tag:blogger.com,1999:blog-66659537969622930712024-03-13T02:18:25.030+02:00Network MuseumA place to share a little bit of the history and the beauty of networks with my students.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comBlogger34125tag:blogger.com,1999:blog-6665953796962293071.post-46627793803385750042016-02-29T15:21:00.001+02:002016-02-29T15:21:48.642+02:00Mobile telephony circa 1990<div dir="ltr" style="text-align: left;" trbidi="on">
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Many people refer to older cellphones as 'brick phones' due to the size of such phones. However, there was a time - in the late 1980s up to about 1990 - when bricks were diminutive in size compared to mobile phones. Those mobile phones were often installed in cars (and therefore were often referred to as car phones). However, many were not permanently affixed to the car and could be carried to wherever they were needed. The lead acid batteries used by those phones were just one of the factors that impacted on their weight. I knew someone who, due to the nature of his work, always carried his phone with him; to be more precise, he hired someone to carry his phone.</div>
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One of the phones dating from this era was the Siemens C30 Flexiphone (circa 1991).</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6xBTkMTRr57BdVmXBIYucIvX39vvPb5yKc6zDIpuoHHRXAaktZw2ZoLAGwOG8zi4ogu5dS2yreM4LnG1cMK5XfgFGosEcTenxoToAAY4y236zopLfoEuc4-mYQEA_kMe8sOGwMsoSc3U/s1600/PK5_7070-klein.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6xBTkMTRr57BdVmXBIYucIvX39vvPb5yKc6zDIpuoHHRXAaktZw2ZoLAGwOG8zi4ogu5dS2yreM4LnG1cMK5XfgFGosEcTenxoToAAY4y236zopLfoEuc4-mYQEA_kMe8sOGwMsoSc3U/s400/PK5_7070-klein.jpg" width="263" /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYLZCuS-OuolgneUB3tjMerkWMx8bYGt3fi5MupkStz8EaLyf5MBbpXhrq0Xbvba05saEsOp5Egn92HUQzHdqWf8IG9u_UbMcxqHFHKz25eu-yloRRunikF8cY_xuja8a7ClqOhFk7B5w/s1600/PK5_7072-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="263" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYLZCuS-OuolgneUB3tjMerkWMx8bYGt3fi5MupkStz8EaLyf5MBbpXhrq0Xbvba05saEsOp5Egn92HUQzHdqWf8IG9u_UbMcxqHFHKz25eu-yloRRunikF8cY_xuja8a7ClqOhFk7B5w/s400/PK5_7072-klein.jpg" width="400" /></a></div>
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The picture above shows the phone as well as a SIM (<i>subscriber identity module</i>) card to be used with it. Note the telephone number embossed on the card, starting with a 081; the cellular networks that appeared a few years later initially used 082 (Vodacom) and 083 (MTN). Other operators that arrived somewhat later on the scene continued this trend. However, cellular operators soon needed larger number spaces for their numbers and were assigned other prefixes. Number portability also meant that the prefix was no longer a reliable indicator of the operator associated with the number.</div>
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The SIM card shown in the picture above was the 'standard' or 'normal' size for SIM cards - the same size as, say, a credit card. However, even in these early cards the electronics were all located underneath the contact points visible on the surface of the card. Over the years smaller and smaller parts of the SIM card were used by cutting away more and more of the redundant plastic. This lead to the introduction of mini, micro and nano SIM cards, that only differ in the amount of plastic left around the electronics. (However, the electronics evolved independently from the decrease in size of the surrounding plastic by, for example, incorporating more memory as time progressed.) People who have never known 'full size' SIM cards often incorrectly refer to mini-SIM cards as full size cards; however, as demonstrated in the picture below, the 'real full size' cards were indeed once upon a time inserted as is in mobile phones.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjh64sJPhh5B4pelMnXJE3huRPME1gcYqKHoymPKh0xvGcUmnPPp-rp-D_F0WazmagLkyozyGCMUIU1MkB6-RjSfIASLYpYlBo6n7bwgFsdWZb4YCJMgBr21AVCwWbrZKjfhBe4MwmoQtU/s1600/PK5_7074-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjh64sJPhh5B4pelMnXJE3huRPME1gcYqKHoymPKh0xvGcUmnPPp-rp-D_F0WazmagLkyozyGCMUIU1MkB6-RjSfIASLYpYlBo6n7bwgFsdWZb4YCJMgBr21AVCwWbrZKjfhBe4MwmoQtU/s320/PK5_7074-klein.jpg" width="320" /></a></div>
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The logic of using such relatively large SIM cards clearly did not stem from the size of the electronics - which for decades were housed under contacts with a standard size. The relatively large size stemmed from the way subscribers were expected to use mobile phones.</div>
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The astronomical cost of mobile phones meant that few members of the public would be able to afford a phone. And very few of those who could afford a mobile phone were going to lug it around with them. The much more plausible scenario was that mobile phones could be installed in taxis and at other convenient places. The subscriber then only had to carry a SIM card along and insert it in the phone in the taxi (or elsewhere). The fact that the subscriber could then make calls would have been convenient. However, the fact that it would be possible to phone the subscriber at his or her personal number at the phone containing the SIM made this a must-have tool for busy executives. A credit card sized SIM was the obvious choice for SIM cards to be used in this manner.</div>
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The Siemens C30 Flexiphone depicted here offered the business executive additional functionality. With an adapter it could be connected to a fax machine, telephone answering machine and even a mobile computer - all in the convenience of one's own car...</div>
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<span style="font-size: x-small;">Phone kindly provided by Peter Fryer of Risk Diversion (Pty) Ltd</span></div>
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Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-15205819943942599962012-04-08T17:48:00.000+02:002012-04-08T19:51:02.993+02:00Peering at JINXThe Internet - or any internet for that matter - is, by definition, a collection of connected networks.<br />
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The Internet started its history in 1969 as the ARPANET when four nodes were connected from four campuses: the University of California Los Angeles (UCLA), the Stanford Research Institute (SRI) in Menlo Park, California, the University of California at Santa Barbara (UCSB) and the University of Utah. The well known map of the ARPANET below shows the original topology.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjz-xHLphoeJ4C0iJBAyMUHkKeKI1vq9FXC0tK1P7avi2QnBe1XhriLIQUYALXbVuZOpH_ZnC-Yj0o_zMfz6S4NDtp-nW958URG6nfJ02HmgQHceZgHuOHRqHXYBId75nLIrPiPFs8Ii9w/s1600/arpanet1969.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjz-xHLphoeJ4C0iJBAyMUHkKeKI1vq9FXC0tK1P7avi2QnBe1XhriLIQUYALXbVuZOpH_ZnC-Yj0o_zMfz6S4NDtp-nW958URG6nfJ02HmgQHceZgHuOHRqHXYBId75nLIrPiPFs8Ii9w/s640/arpanet1969.gif" width="531" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">To the best of my knowledge this map was drawn by Alex McKenzie. His notes are archived by the Charles Babbage Institute who also now owns the copyright. They have given permission for researchers to quote from the notes.</td></tr>
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Even this simple topology (by modern standards) raises a number of interesting questions about interconnecting sites. Since Utah is only connected to SRI, traffic between Utah and UCSB or UCLA has to be relayed via SRI. Who pays SRI for this service? How much does Utah have to contribute to the links between SRI and UCSB and between SRI and UCLA? Is the link between UCSB and UCLA of concern to Utah at all? Of course, this being a US military project at the time made the questions about funding easy to answer. The other question that this old map illustrates is the one about whom a fifth node should connect to: one, two, three or all four other nodes? In a world where countless organisations and individuals connect their networks or individual computers to the network these questions have, in principle, become impossible to answer.<br />
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In fact very few of the myriad of organisations and individuals connected to the Internet have the skills to decide whom to connect to and how to determine sharing costs. Very few of them are willing to relay information for others, and very few of them want to entrust the relaying of their own information to a competing neighbour down the road. And thus emerged Internet Service Providers (ISPs). Rather than connecting to the Internet 'directly' organisations and individuals rather connect to an ISP. This does not remove the interconnection problem - but delegates it to the much smaller (but still large) number of skilled specialists.<br />
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The connection between ISPs is known as peering. (Technically, peering is the connection of two <i>Autonomous Systems</i>, but a discussion of Autonomous Systems will have to wait for another post.) Two ISPs can (and often do) peer with one another by simply connecting their networks to one another and configuring their gateway routers to route traffic according to their agreed upon policies. But, as we have seen above, this solution does not scale and is only appropriate where there is some special reason for individual networks to peer.<br />
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The more general solution is to establish an 'exchange' where all the ISPs in the area can connect to one another. In South Africa at the time of writing the Internet Service Providers' Association (ISPA) operates two such Internet exchanges: one in Johannesburg (JINX, <i>Johannesburg InterNet eXchange</i>) and one in Cape Town (CINX).<br />
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An Internet exchange is often <i>hosted</i> by one of the bigger ISPs. Both JINX and CINX are hosted by Internet Solutions (IS).<br />
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While I would love to post some pictures taken inside an Internet exchange, I haven't even attempted to ask permission to go and take some. I would imagine that such information (in pictures) is rather sensitive and affects the critical infrastructure of a country. So the best alternative is to show the outside of the buildings that house one.<br />
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JINX is indeed housed in two buildings.<br />
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JINX Rosebank is located at 158 Jan Smuts Avenue, Rosebank, Johannesburg.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmBL16yDjvlVOE8V6UUNcjz10kmj59YEgdXpxHtbo6YxgyJ70XOnB-kY9uGq5MIoKi8Uyz-TrrKX7dlQnV4gKVncCowgy3J1pSx98kkHXcI3jE5xo1_Y4j1aNieGo7EydIKK5RRIm7anI/s1600/qqqq0069-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmBL16yDjvlVOE8V6UUNcjz10kmj59YEgdXpxHtbo6YxgyJ70XOnB-kY9uGq5MIoKi8Uyz-TrrKX7dlQnV4gKVncCowgy3J1pSx98kkHXcI3jE5xo1_Y4j1aNieGo7EydIKK5RRIm7anI/s320/qqqq0069-klein.jpg" width="213" /></a></div>
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The satellite and microwave dishes on the balconies are an indication that this is not an ordinary office complex. The JINX Rosebank facility is located in vaults 14 and 16 somewhere on the second floor of this building.<br />
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The picture above was taken from the east. Walking around to the south presents one with the following view. Note again the various dishes on the balcony. The bank of air conditioners may not be easy to see from this angle, but there are indeed many.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrNGpkoYBXcntdv3rLXELSYI5uTPPCIXbgnImmxWO5dGAFEGC-U6iNHLMIKS_ca2eDmgRhYPX9-sXXaeL0UDLPpksRDPYaUEcGQB1WhofPnvwl1gRuSc4IPBNZNsM9fXWTdDNYAwA2uhw/s1600/qqqq0071-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrNGpkoYBXcntdv3rLXELSYI5uTPPCIXbgnImmxWO5dGAFEGC-U6iNHLMIKS_ca2eDmgRhYPX9-sXXaeL0UDLPpksRDPYaUEcGQB1WhofPnvwl1gRuSc4IPBNZNsM9fXWTdDNYAwA2uhw/s320/qqqq0071-klein.jpg" width="320" /></a></div>
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From the west - from Jan Smuts Avenue - it looks as shown in the picture below.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBMLFM7o0K8CcbMp7zxpmOOoKuL4vbVOkn2-LwAs4TbX5YFdPGkw52KmFOLd0xcjIhDDIFfuMlqBk5I85iuGK7Q8IGDMpIGjGNaZqrE50A3G-JUMhLron709WSPAJ4NeNDx_5LHBnuRVU/s1600/qqqq0079-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBMLFM7o0K8CcbMp7zxpmOOoKuL4vbVOkn2-LwAs4TbX5YFdPGkw52KmFOLd0xcjIhDDIFfuMlqBk5I85iuGK7Q8IGDMpIGjGNaZqrE50A3G-JUMhLron709WSPAJ4NeNDx_5LHBnuRVU/s320/qqqq0079-klein.jpg" width="320" /></a></div>
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Finally, looking from the north towards Johannesburg city centre, one sees the billboard of Internet Solutions claiming its presence (amidst others) in this building.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7Efxx-2mdmDq1eCV34Vlm7RofEooy38WIz7PEtgPJmHkNLtes-AunDOWrcOo32eRNExTohgw_9pypeC4TjAG7fpNnBPwn-52qUe8l5uJvagy_haGXoDOJhLRncBW-5XmJqevLrpjkS9M/s1600/qqqq0081-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg7Efxx-2mdmDq1eCV34Vlm7RofEooy38WIz7PEtgPJmHkNLtes-AunDOWrcOo32eRNExTohgw_9pypeC4TjAG7fpNnBPwn-52qUe8l5uJvagy_haGXoDOJhLRncBW-5XmJqevLrpjkS9M/s320/qqqq0081-klein.jpg" width="240" /></a></div>
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As usual a map may be useful to illustrate our journey thus far (as well as the journey that remains). On the map below the JINX Rosebank facility is on the left. We started our journey on its western side - more or less where the label (W) has been added in green. From there we travelled clockwise until we reached its eastern side - more or less where the label (E) has been added in green.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqItIAZ7sHmxnwM8FcllsLQoOhHcyDiGTvXFaCdA8DwANq1yd8RYeFlLfYNpd9y2_iPXsP481yKheY3q4X7Ph7M6q66euMYcY31CRoVVbhNtHGsHOQWSpYuay-J9GqZRzeL84PJiuCvf4/s1600/map.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="204" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqItIAZ7sHmxnwM8FcllsLQoOhHcyDiGTvXFaCdA8DwANq1yd8RYeFlLfYNpd9y2_iPXsP481yKheY3q4X7Ph7M6q66euMYcY31CRoVVbhNtHGsHOQWSpYuay-J9GqZRzeL84PJiuCvf4/s320/map.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Map derived from satellite imagery by Google Earth and others.</td></tr>
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Immediately opposite the JINX Rosebank facility - towards its west in the same street block - is the Parklands Centre which contains the JINX Parklands facility. On the map above we will follow the passage through the Parklands Centre that starts at its eastern side. The picture below looks towards the Parklands Centre - approximately towards the point labelled (E) in yellow on the map. The journey proceeds through the centre of the Centre and exists on the west - just below the spot labelled (W) in yellow. We now enter the Parklands Centre from the east.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiv2G-X4e_KRxEc3GSCzfE8vm9rhxgz96uVmVRhU1wbNtAxLPy3jXYMPd-89kZYNpscdfGqgFQ90otfa1JqjhAgbHyCqictNZZE7eqhXeBzVoTmPdYm_Xz8jZ7W7_lnobM8x6eAfOn6PGs/s1600/qqqq0083-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiv2G-X4e_KRxEc3GSCzfE8vm9rhxgz96uVmVRhU1wbNtAxLPy3jXYMPd-89kZYNpscdfGqgFQ90otfa1JqjhAgbHyCqictNZZE7eqhXeBzVoTmPdYm_Xz8jZ7W7_lnobM8x6eAfOn6PGs/s320/qqqq0083-klein.jpg" width="320" /></a></div>
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Apart from a Post Office, there does not seem to be happening much in the Parklands Centre.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTbjD-zzINTSHgWJ7UW9t0hjIBLQUAjhXlARc9E1rytbjhZ65C3Qs1XzKBA1ld_yFPDhxx5UzNyOGP-3_9wrNU1cqrnc4Af3w5N9oaBkFaqu4lYc8fNOSFGyDN13XF1ktDiqOacf0nN7M/s1600/qqqq0084-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTbjD-zzINTSHgWJ7UW9t0hjIBLQUAjhXlARc9E1rytbjhZ65C3Qs1XzKBA1ld_yFPDhxx5UzNyOGP-3_9wrNU1cqrnc4Af3w5N9oaBkFaqu4lYc8fNOSFGyDN13XF1ktDiqOacf0nN7M/s320/qqqq0084-klein.jpg" width="320" /></a></div>
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But we know somewhere in this centre - to be more precise, in Vault 4 in this centre - is the JINX Parklands facility. Exiting on the east the facade of the building is composed of drab concrete slabs housing what seems like emergency power generators. Pictures from a few years back (which, because of copyright issues I cannot reproduce here) show a facebrick facade starting slightly deeper in. Hence the part housing the generators must have been a fairly recent addition.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPjOwi9Y6ixWKb-chQDxLAJ6LzAri2PLecQwERYu1e29fxDl_Nifi6tmpYtG_9GKR5NYIBn05NRaqfT1Yzid1e8KOEgOgtQfhCwRUDgccd2lKpc81qIG3u44yOzSneVTZg3OpM0_0OKz8/s1600/qqqq0070-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPjOwi9Y6ixWKb-chQDxLAJ6LzAri2PLecQwERYu1e29fxDl_Nifi6tmpYtG_9GKR5NYIBn05NRaqfT1Yzid1e8KOEgOgtQfhCwRUDgccd2lKpc81qIG3u44yOzSneVTZg3OpM0_0OKz8/s320/qqqq0070-klein.jpg" width="320" /></a></div>
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Note that the Rosebank facility (two vaults) and Parklands facility (one fault) have been interconnected to form one virtual Internet exchange. In fact, at the time of writing, the Rosebank facility is filled to capacity and space only remains in the Parklands facility. On a logical level this is unimportant to an ISP that wants to join the exchange. On a physical level it does make a difference - the new ISP's cabling has to terminate in Parklands.<br />
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<span style="font-family: inherit;">More information about the Internet exchanges is available on the <a href="http://ispa.org.za/">ISPA site</a> - click on INX. Interesting information includes the names of the ISPs that peer at JINX (as well as those that peer at CINX). Here are some other FAQs straight from their site:</span><br />
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<span style="color: #666666; font-size: x-small;"><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;"><b>Q</b>: What equipment is required for connecting to an INX?</span><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;"><b>A</b>: You can connect to the INX switch fabric using either a suitable router or a MetroEthernet service. INX switches have copper based Ethernet connections and singlemode or multimode fibre Ethernet interfaces available. You require a router that supports BGP4 since all peering is done using BGP. BGP4 is supported on numerous devices from many vendors. Speak to your router vendor in order to obtain the best hardware. It is common to have dozens of BGP sessions with other members at the exchange and your hardware should be powerful enough to handle this.</span></span></blockquote>
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<span style="color: #666666; font-size: x-small;"><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;"><b>Q</b>: Who can I get backhaul links to an INX from?</span><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;"><b>A</b>: Backhaul links into the INXs are typically provided as either MetroEthernet or SDH circuits over fibre. You can approach any licensed ECNS holder to provide you with these services. A number of ISPA’s large and medium members will already have a point-of-presence (PoP) at or near the INX environment and may be able to provide these services.
For larger capacity circuits it may be feasible to obtain dark fibre pairs or DWDM wavelengths into the INX environment.</span></span></blockquote>
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<span style="color: #666666; font-size: x-small;"><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;"><b>Q</b>: Can I get wireless access to an INX?</span><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif;"><b>A</b>: Roof or tower space near the INXs is normally limited and it is preferable to connect to an INX via a fibre based circuit. Contact the host of the INX you wish to connect to in order to determine the rules and processes for installation of radio equipment.</span></span></blockquote>
<blockquote class="tr_bq">
<span style="color: #666666;"><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: x-small;"><b>Q</b>: What’s the price of a link between Rosebank and Parklands?</span><span style="font-family: 'Helvetica Neue', Arial, Helvetica, sans-serif; font-size: x-small;"><b>A</b>: Existing cables between the Rosebank and Parklands cages are only for peering traffic on the switch fabric. ISPA is not able to provide these links to members. Members should speak to the host or a licensed operator to obtain these cross-connects.
</span></span></blockquote>
<div>
Statistics about the traffic flowing through JINX are available at <a href="http://stats.jinx.net.za/" target="_blank">http://stats.jinx.net.za</a>, and the statistics for CINC at<span style="font-family: inherit;"> <a href="http://stats.cinx.net.za/" target="_blank">http://stats.cinx.net.za</a></span></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-29090543039748253102012-03-15T21:22:00.002+02:002012-03-15T21:22:57.372+02:00The size of the NetIt should be obvious that it is impossible to determine the size of the Internet. However, in the day and age in which we live, if you cannot impress someone with numbers, that someone will usually be unimpressed. Therefore we <i>have</i> to measure the size of the Internet. One of the best surveys of the size of the Internet is conducted bi-annually by the Internet Systems Consortium (isc.org). At least their method is clear and they are aware of the limitations of the method. To see the latest size of the Internet (as well as a host of other interesting statistics) consult their site. Our museum's interest in their numbers is more local.<br />
<br />
The graph below depicts the growth in the size of the Internet in Southern Africa (excluding South Africa) between 1997 and 2012. The growth in some countries (Namibia - yellow, Zimbabwe - green and Mozambique - purple) is impressive. Or, at least, it was impressive until the worldwide economic downturn started.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX82XF5jj71Nkm36aurq7AFeONNt7swG1lNK3Ojy0e4sm6TGcdmtzm1lPKYJSCyla9A2IzserdIXUGQvR5nllHUkpS6D3SXK-9P5-ngNZJE4CbCex8AmGWBey9gGbeO40agNTNivWRSFA/s1600/isc-sa-za.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="277" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX82XF5jj71Nkm36aurq7AFeONNt7swG1lNK3Ojy0e4sm6TGcdmtzm1lPKYJSCyla9A2IzserdIXUGQvR5nllHUkpS6D3SXK-9P5-ngNZJE4CbCex8AmGWBey9gGbeO40agNTNivWRSFA/s320/isc-sa-za.png" width="320" /></a></div>
<br />
Unfortunately the impressive growth in these countries pales when the growth in the regional superpower, South Africa, is added to the picture. The graph below shows the growth in South Africa in red. Relative to South Africa the best performer in the previous graph, Namibia (in yellow), shows hardly any growth at all.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZjXOoe7spKg7j5z0BMzjIVAfCvUGItmelDdMzc599_vomKaQAujqnHs34XMrc44LLRSH43D-vUAxjai0jjhzrYJBb7meYZ_gl7NYX_uX4PxxJhnRCcBNk6iblYKoPS7xIOSeAVU5MrrQ/s1600/isc-southern.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="276" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZjXOoe7spKg7j5z0BMzjIVAfCvUGItmelDdMzc599_vomKaQAujqnHs34XMrc44LLRSH43D-vUAxjai0jjhzrYJBb7meYZ_gl7NYX_uX4PxxJhnRCcBNk6iblYKoPS7xIOSeAVU5MrrQ/s320/isc-southern.png" width="320" /></a></div>
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Of course, anyone who has ever travelled through the beautiful Namib knows that people are scarce in that vast country. In a sense it is 'unfair' to plot Namibia next to South Africa. The graph below 'corrects' this by plotting the number of hosts per thousand inhabitants for each country. (The population sizes are from the WHO site - interpolated and extrapolated where necessary.) This shows that Namibia now becomes visible next to South Africa. However, the other Southern African countries still have hardly any presence on the Net compared to South Africa and Namibia.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB-WOsKKI88VHpk6KJUSTxkxPTtSoMhB2P5txbSWEXmv_tg0l6Ys-mFLQJB8NmhvobyFahuTuf2XTG7KdoxD2v92W5u_pv5zNIYs7m6hqwcFyQX7PKDpcSYMMpmz_tsaL2FKpiLAO_E6w/s1600/isc-who.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="289" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB-WOsKKI88VHpk6KJUSTxkxPTtSoMhB2P5txbSWEXmv_tg0l6Ys-mFLQJB8NmhvobyFahuTuf2XTG7KdoxD2v92W5u_pv5zNIYs7m6hqwcFyQX7PKDpcSYMMpmz_tsaL2FKpiLAO_E6w/s320/isc-who.png" width="320" /></a></div>
<br />
In the global context even the overwhelming regional growth in Internet size in South Africa pales. The graph below shows Japan (in pink), Germany (in green), Australia (in beige) and a couple of other countries. South Africa is shown in red - almost a flat line next to countries elsewhere in the world. Note that the country plotted in yellow in this graph (next to South Africa) is Portugal.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2TqCdSvANE_DOvxQfMAhbPsHoHNfgAg__MCGTu6mphcEz7dT2XMoV4BGK4tF5WdPb9nU8CLWKJM70AyuhXsuJYBa17BfmJ6fR0hJ3QOSRdb771W0-sYEaSsAHAEmUli8GcndS4bY7-Vw/s1600/isc-world.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="283" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg2TqCdSvANE_DOvxQfMAhbPsHoHNfgAg__MCGTu6mphcEz7dT2XMoV4BGK4tF5WdPb9nU8CLWKJM70AyuhXsuJYBa17BfmJ6fR0hJ3QOSRdb771W0-sYEaSsAHAEmUli8GcndS4bY7-Vw/s320/isc-world.png" width="320" /></a></div>
<br />
Before concluding that South Africa is on the wrong side of the digital divide it should be noted that the .za TLD ranks 23rd on the list of 270 TLDs measured in the January 2012 survey. Lesotho is at position 189. We leave it to the reader to consider the location(s) of the global digital divide(s).Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-53232132091605600102011-10-25T23:11:00.000+02:002011-10-25T23:11:23.038+02:00A brief history of the cloud - as I recall<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvgIGXKag7EZZ882e6uxFgX418sj7XRTwxpL8FgqVIMq3Fd-YCuBrcTzWjnB6KlM3YHYqrnnMrSArG9SA7PWf4gYfm0oSHfG_o2Pu7cV_g8HapRyZwkRtU4ZORsmIoVxjwkBT4oWkHcn0/s1600/PK5_4467-piepklein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="161" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvgIGXKag7EZZ882e6uxFgX418sj7XRTwxpL8FgqVIMq3Fd-YCuBrcTzWjnB6KlM3YHYqrnnMrSArG9SA7PWf4gYfm0oSHfG_o2Pu7cV_g8HapRyZwkRtU4ZORsmIoVxjwkBT4oWkHcn0/s320/PK5_4467-piepklein.jpg" width="320" /></a></div>
<br />
Once upon a time wide area networks (WANs) had topologies. Lines (or sometimes waves) would connect the various nodes or sites. And whether the WAN was spread across a campus or across a country, one could somehow represent the network using a map.<br />
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The lines that crisscrossed the country typically belonged to some national operator, but the company that rented it sort of 'owned' it and could use (or waste) the available bandwidth in whatever way it wished. The problem, of course, was that while they constantly had the bandwidth available, they also constantly paid for the bandwidth. For busy lines this was sometimes cost-effective. For occasional connections one could consider dial-up links that would only establish the link when necessary. However, in many cases (including frequent but brief communication) a permanent link where one <i>only</i> paid for what was actually transmitted would be a better solution.<br />
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A concomitant problem occurred where the links spanned national boundaries. Within a country a line could be leased from the national operator, but there was no 'international' operator from whom one could lease a line from, say, Cape Town to Cairo.<br />
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The solution to both these problems came in the form of PDNs, which is an acronym for <i>public data networks</i> and/or <i>packet data networks</i>. The networks were public in the sense that they were originally still operated by the national operator and any company (or wealthy individual) could connect to the PDN. They were packet-based because messages were split into packets and packets were intermingled with other users' packets on the same wires, but routed to the correct destinations where the messages were reassembled.<br />
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The first incarnation of these PDNs was X.25 networks. In those days the South African Post Office was the national network operator in South Africa, and the national leased line infrastructure known as SAPONET (for <i>South African Post Office Network</i>). When the (then) new packet-oriented X.25 network was introduced it was called SAPONET-P. The old SAPONET network was renamed to SAPONET-C to emphasise that it used circuit switching.<br />
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One problem that arose with these new networks was that one did not know where the links were. However, one of the major benefits of these networks was that one did not need to know where the links were: It was the operator's responsibility to route packets from their origins to their destinations. It was no longer the user's problem if its link between its Cape Town and Johannesburg offices was down. One transmitted a packet into the network and it was then the operator's responsibility to get it to its destination - using whichever route the operator preferred. The network became a fuzzy entity where users could be blissfully unaware of how it was configured or operated internally.<br />
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Textbooks from the late 1980s soon began representing such WANs as clouds. Exactly how 'realistic' the cloud was drawn depended on the preferences of the author or the publisher. Similarly, anyone who presented a lecture on networking <i>had</i> to draw some clouds during the lecture, which were often drawn with great flair.<br />
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The X.25 cloud was interesting in part because of the set of standards that operated outside, inside, across and between clouds. The book in the bottom left quadrant of the picture above (Uyless D Black, <i>Computer Networks: Protocols, Standards, and Interfaces, 2nd ed,</i> 1993) nicely illustrates where these standards were 'located'. Note, in particular, X.75 that enables different national networks to be interconnected - linking one country's cloud to that of another country.<br />
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Various other incarnations of PDNs followed, including frame relay and ATM. While some netwoks using these technologies still exist (and are often actively used) the trend is to move to TCP/IP. Over time most of the clouds converged and became a single cloud known as the Internet. And for a while the Internet was a cloud - <i>the</i> cloud - but nobody thought it was a big deal.<br />
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But what was changing was who was communicating with whom. In the days of X.25 a company typically communicated with its branches. In some cases some companies did communicate with others. Initial bank networks, for example, connected a bank's branches with its central offices. However, different banks for a long time after they began using networks still communicated in a primitive manner. In South Africa the Automated Clearing Bureau (ACB) was established in 1972. Banks would send tapes with details of their transactions every evening to the ACB, where the tapes where processed and it was (automatically) determined how much the various banks owed one another. In the early 1980s a few brave banks in South Africa connected directly to one another's networks, but most preferred to connect via a central service that was established by the banks and called SASWITCH.<br />
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The 1990s saw terms such as B2B (<i>business to business</i>) and B2C (<i>business to customer</i>) emerge to focus on this changing landscape. Eventually services like eBay and Webmail arguably implemented 'C2C' (<i>customer to customer</i>) networks, although I have never seen the term C2C used in a technical context. Web 2.0 - with its user-provided content - is another example of C2C communication, although its protagonists probably did not foresee the extent to which these 'users' would actually be C2C (<i>commodity to commodity</i>) communicators in a twisted post-modern world where the consumer has become the commodity and vice versa.<br />
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Initially these changing communication patterns had little impact on the cloud(s). The business (or consumer) was merely communicating with the other business (or consumer) via the cloud using the same old (or, at least, similar) protocols that were used earlier. But where the primary problem earlier was to communicate between specific places (such as, say, Johannesburg and Bloemfontein), the focus changed to get to information or a service irrespective of where it was. The business in Bloemfontein can host its Web presence at an ISP in Cape Town - and then move it to an ISP in Pretoria without users knowing or noticing (unless they wish to).<br />
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I remember the strange experience many years ago when I phoned AT&T's helpdesk in Johannesburg, but got the distinct impression that the call was answered somewhere in Europe (from the accent of the person who answered the call, the latency on the line and some other clues). In fact, call-centres were one of the early services to be relocated to anywhere it was convenient. The local 'call-centre' would consist of a telephone number and the necessary circuitry to forward the call as voice data over the network to the real call centre located where labour and/or facilities where cheaper. In the simplest cases it meant that a call-centre was not required to be everywhere, but local numbers could make it appear that help was only a local call away.<br />
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In the same way any service that primarily provided information or digital goods could be located or relocated anywhere. In the simplest cases companies' Web and email servers no longer needed to be on-site; they could be managed by a service provider anywhere on the network. An entire industry came into being to provide such services, and the number and variety of services increased. Initially the companies offering these services were simply on the 'other side' of the cloud: one knew where they were. One still used them with the same old protocols that entered the cloud at some local ingress point and exited the cloud at an egress point at the destination - and the response used the same mechanism in reverse. But quickly things became fuzzier. It is now much harder to say where, say, <span class="Apple-style-span" style="font-family: 'Courier New', Courier, monospace;">google.com</span><span class="Apple-style-span" style="font-family: inherit;"> or </span><span class="Apple-style-span" style="font-family: 'Courier New', Courier, monospace;">f.root-servers.net</span><span class="Apple-style-span" style="font-family: inherit;"> is. At the time of writing many South African readers are probably unaware that much of their communication with Google actually occurs with a Google cache in Cape Town, and that many of their DNS requests (on root level) are resolved by a root name server in Johannesburg, whereas those using the Internet elsewhere in the world when talking to these 'same' entities are talking to physical machines located on other continents. And all of this happens transparently to the user. The information no longer comes from the other side of the cloud - it comes from somewhere inside the cloud; it comes from who knows where.</span><br />
<span class="Apple-style-span" style="font-family: inherit;"><br /></span><br />
A brief description of the history of clouds should also consider what one uses in the cloud: Is it data, an application, a platform, infrastructure, or something else? However, this post is already stretching the limits of brevity, and those facets of the history of clouds will have to wait for a later post.<br />
<blockquote class="tr_bq">
<blockquote class="tr_bq">
<div style="text-align: center;">
<i>"I've looked at clouds from both sides now,</i></div>
<div style="text-align: center;">
<i>From up and down, and still somehow,</i></div>
<div style="text-align: center;">
<i>It's cloud illusions I recall,</i></div>
<div style="text-align: center;">
<i>I really don't know clouds, at all."</i></div>
</blockquote>
</blockquote>
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<br />Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-76450904476601885732011-09-11T12:33:00.000+02:002011-09-11T12:33:37.357+02:00An ATM switchAsynchronous Transfer Mode (ATM) is a networking technology that routes cells (that is, small, fixed-size packets) of data from one end of a network to the other. <br />
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A link between any two switches is divided into multiple channels by using multiplexing. These virtual channel links are numbered with a number called a <i>virtual channel identifier</i> (VCI). That is, any given physical copper cable, optical fibre or other link between two ATM switches consists of multiple (possibly thousands of) virtual channels. When a connection is established it is necessary to find a series of virtual channels (each obviously on a physical link) that connects the two endpoints of the connection. A series of virtual channel links are known as a <i>virtual path</i>, which is identified by a <i>Virtual Path Identifier</i> (VPI). The VPI and VCI are fields in the header of a cell. Whenever a cell arrives at a switch, the switch in essence performs a table lookup using the VPI/VCI pair, as well as the interface on which the cell arrived. From the table it determines the VPI and VCI that should be used by the next switch; it replaces the VPI/VCI fields in the cell header and then forwards the cell through the appropriate network interface.<br />
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Given the description above we can now look at an ATM switch. The switch we will use is FORE System's ForeRunner ASX 200. It looks as follows:<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiymKeEP16Ugrnq5ComecKGUB3y8tUyUd8qbqkKLn4-EDCB7UtqciYD93idtTQw0JfsBPRD8CT1A80g4ivuQTbdIxKA4Wwp3aPv59jcy5bqVjabffhQPwawntYNFh9nhHhONWeH2FUUSAQ/s1600/IMGP0125b-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="232" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiymKeEP16Ugrnq5ComecKGUB3y8tUyUd8qbqkKLn4-EDCB7UtqciYD93idtTQw0JfsBPRD8CT1A80g4ivuQTbdIxKA4Wwp3aPv59jcy5bqVjabffhQPwawntYNFh9nhHhONWeH2FUUSAQ/s400/IMGP0125b-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">ForeRunner ASX 200</td></tr>
</tbody></table>
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Just below the unit's name are four slots, labelled A, B, C and D. The network media will be connected to the modules in these slots. Slot A is currently empty with a blank plate covering it. Slots C and D contain identical modules and slot C contains a different module. We will return to these modules later.<br />
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Just underneath these four slots is a 'drawer' that contains the <i>switch board</i> or <i>switch fabric</i>. It contains the VPI/VCI lookup tables. However, doing a simple table lookup for every cell won't enable the switch to maintain the speed it should. Therefore the <i>fabric</i> is more than just a set of tables.<br />
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Below the switch board is another 'drawer' which is the processor (or computer) that controls the switch. It is therefore aptly called the <i>switch control processor</i> (SCP). It contains a SPARC processor, some memory, control logic and a hard disc. On the front panel of the processor are a couple of connectors. The two serial ports may be used to connect a terminal to the switch. One may then interact with the SCP via the terminal. There are two ports so that one may connect a local terminal, as well as a remote terminal via a modem to the SCP. The Ethernet connector enables one to connect the SCP to a network (via an Ethernet MAU) and then manage the switch via the network. In addition the front panel contains a reset facility and some status LEDs.<br />
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In the next picture the 'drawer' containing the SCP has been partially opened. (Also note that the network modules that were in slots B, C and D have been removed.)<br />
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<tr><td class="tr-caption" style="text-align: center;">Switch with SCP partially opened.</td></tr>
</tbody></table>
When the SCP is removed fully it is possible to see the processing ICs, as well as the hard disc at the rear.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9dJJMGBSefQHVAzUBVfKarnaXCf1GIhDIE4ahGW3ODFVCMWqizK8nbaON7BXBK92hptUq33jLTlscYZD3mmUCalBjUBIcMJwy19tzIzmsV6V2WH0ekf3_CCkuL59zb6guE5kWLgJu9jY/s1600/P1010325-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9dJJMGBSefQHVAzUBVfKarnaXCf1GIhDIE4ahGW3ODFVCMWqizK8nbaON7BXBK92hptUq33jLTlscYZD3mmUCalBjUBIcMJwy19tzIzmsV6V2WH0ekf3_CCkuL59zb6guE5kWLgJu9jY/s400/P1010325-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The SCP from above. Note the hard disc towards the rear<br />
and the processor below the transparent glass.</td></tr>
</tbody></table>
The SPARC processor glistens like a jewel on the SCP.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDJ4EP2sVooSmgkrD_dfB2QayN-mOHoHwStTiCr9As3VAQmrWmIYbqBO7I6kul1F8x_Z2iZfV4Q6RmafTa-GIwQoi47XlQyrMyoeUxTA0SDmhq10lBfKx-cTturKTM0jreqPlASISDDs8/s1600/P1010322-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="277" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDJ4EP2sVooSmgkrD_dfB2QayN-mOHoHwStTiCr9As3VAQmrWmIYbqBO7I6kul1F8x_Z2iZfV4Q6RmafTa-GIwQoi47XlQyrMyoeUxTA0SDmhq10lBfKx-cTturKTM0jreqPlASISDDs8/s400/P1010322-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A closer view of the Sun SPARC processor</td></tr>
</tbody></table>
As noted above, the 'drawer' just above the SCP contains the switching fabric. The next picture shows it removed from the chassis.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwpqrinkaFvLh8w_yH5SxXz_NGpDWW-YETHnutTzoEL_hbrbSsgD-J4ox1rD0nry_OF7LsY6xc66UTAo9PhSexBU6dXdMnri-iBjLW2qZoMk9oVIUwApYTNRXW5694Q4mKn0mg61o_-uI/s1600/IMGP0130-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="265" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwpqrinkaFvLh8w_yH5SxXz_NGpDWW-YETHnutTzoEL_hbrbSsgD-J4ox1rD0nry_OF7LsY6xc66UTAo9PhSexBU6dXdMnri-iBjLW2qZoMk9oVIUwApYTNRXW5694Q4mKn0mg61o_-uI/s400/IMGP0130-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The switching fabric removed from the chassis.</td></tr>
</tbody></table>
The switching fabric contains the slots into which the network modules may be plugged. Note, in particular, the four sockets at the rear of the slots for these modules. The remainder of the switching fabric consists of ICs that facilitate the connection of the interfaces on the network modules with one another as specified by its current VPI/VCI tables.<br />
<br />
Now that the supporting infrastructure has been discussed the four slots that contain network modules can be revisited. This switch can maintain a speed of 2.5Gbps. The capacity is spread equally over the four slots, meaning that every slot can contain a module that will be able to communicate at a sustained 2.5Gbps/4 = 625Mbps. One may either install a module that uses all this bandwidth for a single high-speed medium, or one may install a module that distributes the capacity over several links. The module in slot B contains six (actually six transmit/receive pairs of) connections that each is able to maintain a speed of 625Mbps/6 = 105Mbps. The modules in slots B and D each has four connectors. Each connector should therefore be able to maintain a speed of 665Mbps/4 = 166Mbps.<br />
<br />
The modules in slots B and D are labelled NM-4/155UTP5EC. Reading this label from the left identifies it as a (network) module with 4 ports each operating at 155Mbps over UTP category 5 cable. Somehow the EC indicates that it uses SONET framing (in contrast to a similar model that has only a C in this position and that uses SDH framing). The differences between the SONET and SDH standards are small, but technical and not important for the purposes of this museum. Note that the actual SONET/SDH speed used is 155.52Mbps.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCSfi_KNmpyrJVcy6sO-n7OAdd_BagrwJr3VFGNACSGKeFt-JNe4Auuc1iIw25O-NRQ5aNLuiCatrXeBe_ZNzeNr4SyxEwS5jcAufN9BQWgPjh9ayr6a2_1Sy7R6BL8sZAr6VXX1PeNmw/s1600/P1010328-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="267" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCSfi_KNmpyrJVcy6sO-n7OAdd_BagrwJr3VFGNACSGKeFt-JNe4Auuc1iIw25O-NRQ5aNLuiCatrXeBe_ZNzeNr4SyxEwS5jcAufN9BQWgPjh9ayr6a2_1Sy7R6BL8sZAr6VXX1PeNmw/s400/P1010328-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The NM-4/155UTP5EC modules in slots B and D</td></tr>
</tbody></table>
The network modules are designed to be easily removable. The next picture shows one of the modules partially removed.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgawXgkiEtf-s62vDsi36s_lBUfaTSeGboGbEBiBnuN9GBwmmvTADxnlxpigNKkqNfCgBkNFvgl0GBSEls29FvrEdRO_AqEcirlBxmFjDLpBq36mCh2B-4W-6q8Rx34SUFO9_kpaLlkgiw/s1600/IMGP0127-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="245" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgawXgkiEtf-s62vDsi36s_lBUfaTSeGboGbEBiBnuN9GBwmmvTADxnlxpigNKkqNfCgBkNFvgl0GBSEls29FvrEdRO_AqEcirlBxmFjDLpBq36mCh2B-4W-6q8Rx34SUFO9_kpaLlkgiw/s400/IMGP0127-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">An NM-4/155UTP5EC module partially removed.</td></tr>
</tbody></table>
In fact, the switch was designed to enable hot swapping of these modules. If a module fails it may be removed from the switch and replaced by a similar module without affecting the rest of the network. The replaced module resumes operation as soon as the new module is plugged in.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwKBi7jrDOg_t7uPgqfeSiMpx1Plh6w6fMvVw-8gXUN3-G3IJlkY-aiTqRahcTp8gzs7mrMnmF7ym49QwBXjQHd5ShjsQWgwbD00jMFnDzHK676-s5raAeUpKTvi7GEBF8I-tSD5ZMh5E/s1600/P1010327-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="396" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwKBi7jrDOg_t7uPgqfeSiMpx1Plh6w6fMvVw-8gXUN3-G3IJlkY-aiTqRahcTp8gzs7mrMnmF7ym49QwBXjQHd5ShjsQWgwbD00jMFnDzHK676-s5raAeUpKTvi7GEBF8I-tSD5ZMh5E/s400/P1010327-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">An NM-4/155UTP5EC module viewed from the top.</td></tr>
</tbody></table>
The other module in the switch is an NM-6MM/125B is somewhat more of a conundrum, since I have been unable to find detailed information about it, and its naming convention is different from other modules. It clearly is a module with 6 optical fibre ports. In other modules MM indicates that it uses multimode optical fibre (but the MM usually follows the slash, rather than precedes it). The 125 in the context of fibre may mean 125µm fibre, but this is purely guessing.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKltVYMdWa0_GE7whmPY6WzbdmvtnVH8X9gO90Ber0PdgpQBYUeCzoHYMC6qpi29f3ujGSACZxXxjQxk1TxCsrsJ5jx04G5tE0eFMR4Hz3xypWo0VcsQ_0VcbgcQ8Ym-YTX_wZC-TRboc/s1600/IMGP0128-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="253" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKltVYMdWa0_GE7whmPY6WzbdmvtnVH8X9gO90Ber0PdgpQBYUeCzoHYMC6qpi29f3ujGSACZxXxjQxk1TxCsrsJ5jx04G5tE0eFMR4Hz3xypWo0VcsQ_0VcbgcQ8Ym-YTX_wZC-TRboc/s400/IMGP0128-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The NM-6MM/125B module in slot C (as well as the covered empty slot A).</td></tr>
</tbody></table>
The next picture contains a slightly closer view of the NM-6MM/125B module.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdkC32S-yT_SGKTB0kox9D226SlZDKJM4QF6H9J99kmOhUH1atFGzeO8NyFFh9fTiO3heJGlCHKaQu2AiQUzugmX8facz2jHz0bhAweHaWSBgnzCSSTbyj8S9pEPFmjtOYp0iU6GChoGE/s1600/P1010324-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="202" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdkC32S-yT_SGKTB0kox9D226SlZDKJM4QF6H9J99kmOhUH1atFGzeO8NyFFh9fTiO3heJGlCHKaQu2AiQUzugmX8facz2jHz0bhAweHaWSBgnzCSSTbyj8S9pEPFmjtOYp0iU6GChoGE/s400/P1010324-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The NM-6MM/125B</td></tr>
</tbody></table>
Turning one the power lets the switch erupt in colour as only network devices can.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGLQWUQu9V16_jxv_Dhie35JdVBGB6GzDJc6Vt0AoNyYfE-WITMS7COQLOngPvuVqu0YICQX03n3y_OH1HrzX1QOLZj-vClgIdxsqwmiIa69B3gME3EcyJ3Ur4oJ0eWCxNG3CC05l0Tsc/s1600/PK5_4456-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="173" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGLQWUQu9V16_jxv_Dhie35JdVBGB6GzDJc6Vt0AoNyYfE-WITMS7COQLOngPvuVqu0YICQX03n3y_OH1HrzX1QOLZj-vClgIdxsqwmiIa69B3gME3EcyJ3Ur4oJ0eWCxNG3CC05l0Tsc/s400/PK5_4456-klein.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">ForeRunner ASX 200 powered up</td></tr>
</tbody></table>
The final picture shows the switch, an 18" ruler (underlining the fact that the switch is intended for a 19" cabinet), as well as the network modules outside the chassis.<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8x0-lELGjXizyZmVxJic_q-X2IaxacVK5Q_FhukeSjfpm2XONlzPt8olIUNSmV3kAwM81WDvRXb-kp89W3ovjsrVijxSbEfms_z1EtZjWCG2G5-bi0iZ7AWkJPyA_ngVx0XcsA8lKDpc/s1600/IMGP0129-klein.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg8x0-lELGjXizyZmVxJic_q-X2IaxacVK5Q_FhukeSjfpm2XONlzPt8olIUNSmV3kAwM81WDvRXb-kp89W3ovjsrVijxSbEfms_z1EtZjWCG2G5-bi0iZ7AWkJPyA_ngVx0XcsA8lKDpc/s400/IMGP0129-klein.jpg" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">ForeRunner ASX 200 with network modules.</td></tr>
</tbody></table>
The ForeRunner ASX 200 was built by FORE Systems. FORE Systems was established in 1990 by four researchers from Carnegie Mellon University, Francois Bitz, Onat Menzilcioglu, Robert Sansom, and Eric Cooper, whose first letters from their first names were used to form the acronym FORE. FORE Systems soon became a player to be reckoned with in the telecommunications space - in particular due to their excellent ATM switches. In 1999, a British company, General Electric Company, bought FORE to put itself in a stronger position in the US. Long before this, in 1968, General Electric bought Marconi Wireless Telegraph Company. Long story short: In 2003 General Electric Company decided to change their own name to Marconi Corporation. In 2005 most of Marconi (including what used to be FORE) was sold to Ericsson.<br />
<span id="goog_5650746"></span><span id="goog_5650747"></span>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-38651217782322211722011-08-13T15:19:00.000+02:002011-08-13T15:19:29.626+02:00BeltelIn the late 1970s Bulletin Board Systems (BBSs) emerged. They were systems maintained by computer enthusiasts who referred to themselves as SysOps (system operators). A SysOp would provide the BBS and link it via one or more modems to the telephone service. Other users could then dial into the BBS and leave messages for other users, retrieve messages and upload or download software and other files.<br />
<br />
Soon after that telecomms companies started experimenting with similar technology. BBSs initially allowed users in the local BBS community to exchange information and files. In contrast, the telecomms companies could convince other businesses to link to their systems as service providers. The telecomms companies also had billing arrangements with consumers in place and therefore were able to facilitate selling of information and software and ensure that payment flowed from buyers to sellers.<br />
<br />
The systems adopted by telecomms companies were generally known as Videotext systems. In the UK the videotext system was known as Prestel; in many other countries systems were developed that were to a greater or lesser degree based on Prestel. In 1986 the Sout African version, known as Beltel, was introduced by the South African Post Office (who then also operated the country's phone system). Like other Videotext systems, it allowed communication via a 40-column 'terminal'; it also allowed chunky block graphics where every character could be divided into four 'pixels'.<br />
<br />
Back then the Internet was still a scientific/academic network. In contrast, the Videotext services were commercial and provided a platform for e-commerce to develop. Below is a picture of the 1996 Services Directory containing about 20 pages of lists of businesses that were connected to Beltel, waiting for business from Beltel users.<br />
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</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhItZSFg2UdskbJRjfmgyYrqz5pHxmKN-r5-62-4_PEJ4uYo3h99cj1kB_rqsHyRLt3N9KJwHxdAvXRfBfa6HfjCs0khACr3ZRjMGeA6lo2kPdNOCjnUaOaVdG5OJKPpD9u_Cs8TRiHBu0/s1600/beltel1-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhItZSFg2UdskbJRjfmgyYrqz5pHxmKN-r5-62-4_PEJ4uYo3h99cj1kB_rqsHyRLt3N9KJwHxdAvXRfBfa6HfjCs0khACr3ZRjMGeA6lo2kPdNOCjnUaOaVdG5OJKPpD9u_Cs8TRiHBu0/s320/beltel1-klein.jpg" width="223" /></a></div>In addition to the directory of service providers, the directory also provided some other information. Page 2, for example, answered the question: What is Beltel?<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDELTQpE1U-EE4kpKhLp0q4XvvcirdygDG_S75ws1IoLy4p4F8NSg_I7QVr5G4CkH0rhHzF85FHdpTygCfjAgtP2fPYACEvHRHAvPdjfYWp78v_IA8PI70IQVHiiWwsF-xQohXzJh89UA/s1600/beltel2-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDELTQpE1U-EE4kpKhLp0q4XvvcirdygDG_S75ws1IoLy4p4F8NSg_I7QVr5G4CkH0rhHzF85FHdpTygCfjAgtP2fPYACEvHRHAvPdjfYWp78v_IA8PI70IQVHiiWwsF-xQohXzJh89UA/s320/beltel2-klein.jpg" width="224" /></a></div>Page 25 listed the Beltel tariffs.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVCY8eVOV91BeXu3AH2wGaomC_W4IZFrhTs9tcK2Mh2FrgXLLQjsaxgmu_V-slMIc-YjHHJHNGNCshE9ocTBkUvV8aIMU5rVN9aeJ253MoDtzL-mdapUhVbQlvkH0w2iaaYE2c-Luse-Y/s1600/beltel3-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVCY8eVOV91BeXu3AH2wGaomC_W4IZFrhTs9tcK2Mh2FrgXLLQjsaxgmu_V-slMIc-YjHHJHNGNCshE9ocTBkUvV8aIMU5rVN9aeJ253MoDtzL-mdapUhVbQlvkH0w2iaaYE2c-Luse-Y/s320/beltel3-klein.jpg" width="225" /></a></div>To use the system one either used a dedicated terminal (known as a <i>Minitel</i>) to connect to the system, or one used an ordinary PC with special software installed. The software used with Beltel was known as PCbel and came on a floppy or, later, on what is in South Africa known as a stiffie.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihS1jmbKGzhFW6MfTPMREH1n_CPzqBFIt9rYwrvru5VDuLKNhA2vE5b0Z49TVVYx6oEiIlq1fhWBck4TO2RapUiEH6qDnKjDGCrKpH6in1R0KPSncbGm-Ztk8ZajNgRc9WXasL5XTWumo/s1600/beltel5-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihS1jmbKGzhFW6MfTPMREH1n_CPzqBFIt9rYwrvru5VDuLKNhA2vE5b0Z49TVVYx6oEiIlq1fhWBck4TO2RapUiEH6qDnKjDGCrKpH6in1R0KPSncbGm-Ztk8ZajNgRc9WXasL5XTWumo/s320/beltel5-klein.jpg" width="318" /></a></div>I just placed the PCbel diskette depicted above in my PC and it still seems readable (but not without some complaints from the system). The floppy contains two files:<br />
<br />
<ul><li></li>
<li><span class="Apple-style-span" style="font-family: 'Courier New', Courier, monospace;">install.exe, which is</span> 18368 bytes long and dated 22 January 1993 </li>
<li><span class="Apple-style-span" style="font-family: 'Courier New', Courier, monospace;">newpcbel.exe</span> , which is 168925 bytes long and dated 27 January 1993 </li>
</ul><br />
The primary use of Beltel for many of us was online banking. Years before Internet banking was 'invented' we banked online via Beltel. Here is an example of an online payment to a supplier.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_lqkzP0EXJbLXdY3V6aAks8Diu_5dtSGui9fGH3DGr99nzjLp5l5QVWxCN56T0J-ENirkCy9S5G472zD28W7aqgWlj4yUKJrvLjAmquhWycNY8TYdGXVp27DQqZKvmDS59Z3N4Y9FQsk/s1600/beltel4x-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="315" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_lqkzP0EXJbLXdY3V6aAks8Diu_5dtSGui9fGH3DGr99nzjLp5l5QVWxCN56T0J-ENirkCy9S5G472zD28W7aqgWlj4yUKJrvLjAmquhWycNY8TYdGXVp27DQqZKvmDS59Z3N4Y9FQsk/s320/beltel4x-klein.jpg" width="320" /></a></div>The printout is, in essence, a screenshot of what appeared on my screen when I made the payment. Note the width of 40 columns and height of 24 rows. Note the menu system used for navigation: On this particular screen one could press I for the index, E for the end (of interacting with this particular information supplier) and so on. In the top right hand corner is the amount I had spent thus far: 0,0c - that is, nothing. Banks did not charge for using their services via the Beltel billing system; they rather levied charges directly from the customer's account with them.<br />
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The printout above is dated 28 February 1999, which means it dates from fairly late in Beltel's history. As the Internet developed the use of Videotext systems declined and eventually were withdrawn. My bank 'forced' me to move to Internet banking by increasing its monthly fee for Beltel banking to an exorbitant amount, while Internet banking was offered at a low fee (and eventually free).<br />
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Earlier in the history of Beltel it was assumed that few users had printers at home. When one joined Beltel banking the bank typically gave one a folder in which to keep a record of one's transactions. First National Bank called their Beltel bank <i>Videobank</i>. Below is my folder for such record keeping. Page 1 is unfortunately missing. The first entry on page 2 is dated 29 December 1993. Extrapolating to page 1 suggests that I started using online banking around August 1993 - about 18 years prior to this post.<br />
<div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdK80IHWOZGedNCy0WygJ7JkmVYHbQ_tjcN6GFpXrfumq17U5SmPxuTHAgyb9q8xY8Udlw0hBR05BkmG3OTAytTeo9ZQAY7OJMeaxvTAGWDYnwCeHM9GRjU4KplIysp2EhkVfRNo3RPTg/s1600/beltel6-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhdK80IHWOZGedNCy0WygJ7JkmVYHbQ_tjcN6GFpXrfumq17U5SmPxuTHAgyb9q8xY8Udlw0hBR05BkmG3OTAytTeo9ZQAY7OJMeaxvTAGWDYnwCeHM9GRjU4KplIysp2EhkVfRNo3RPTg/s320/beltel6-klein.jpg" width="163" /></a></div><br />
Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-62075824435091259152011-08-01T22:08:00.000+02:002011-08-01T22:08:11.718+02:00RS-232-C breakout boxIn years gone by the primary interface used for communicating data was the serial interface. Its name stems from the fact that data was communicated one bit at a time, one bit after another - that is, serially. The alternative was a parallel interface, where all the bits making up, say, a byte would be communicated in parallel. In principle a parallel interface is faster, but also more expensive since it needs one circuit for every bit, whereas serial needs a single circuit to communicate one bit at a time. Most current data communication technologies use serial transmission: USB, Ethernet via coax, Firewire, Ethernet via UTP at 100Mbps or less, etc. Where the water is muddied somewhat is at the faster communication rates: Ethernet via UTP at gigabit speeds tend to transmit two bits in parallel...<br />
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For many, many years the most popular standard was RS-232 (that is Recommended Standard number 232 of the Electronics Industries Association or EIA). The standard was issued in a number of versions, with B, C and D suffixed to the later versions. However, industry did not see the need to proceed beyond the C-version, and RS-232-C was therefore the standard used in practice.<br />
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Despite being a standard one often spent countless hours trying to get two pieces of equipment to talk to one another. Some of the problems stemmed from the fact that few vendors' products really complied with the standard. Other problems often stemmed from the way the communication interfaces were used: The standard really specifies a way to interface a computer to a peripheral unit. Clearly, the more interesting option was to get two computers to talk to one another.<br />
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Given such a myriad of problems every self-respecting data communication fan had a breakout box.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBeBAlw3_zWu1khA_PcI67zaJzt0mA4QuzyTEnPk5P6suqyrvcp4aQgG4HNkD1M76DSUxkiZxtslfE2Jm69KPVLBW61fJGeMRON5eMC2WCUKZ4AFmL-6SNm725X1T2ylprp1y6YkmWTRE/s1600/pk5_4240-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhBeBAlw3_zWu1khA_PcI67zaJzt0mA4QuzyTEnPk5P6suqyrvcp4aQgG4HNkD1M76DSUxkiZxtslfE2Jm69KPVLBW61fJGeMRON5eMC2WCUKZ4AFmL-6SNm725X1T2ylprp1y6YkmWTRE/s320/pk5_4240-klein.jpg" width="227" /></a></div>The picture above illustrates such a breakout box. It contains two plugs that enable it to be inserted into a serial link. A number of LEDs allow one to observe the voltage level on some of the wires. A number of switches allow one to make or break a specific connecting line between the two communicating units. A number of sockets allow one to jumper one wire to another. These aspects are illustrated in more detail below.<br />
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The standard specifies four facets of serial communication: mechanical, electrical, functional and procedural. The first, mechanical, recommends that a 25-pin DB-25 plug should be used. This breakout box complies with that specification. On the box itself a female DB-25 socket is available.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_ucGM8vC2MOGMWFaLaLqQ62eGw1kf3mjhK8pPlpfvaqEWEycZvpxELCRu_oNPs1EYCrOg7dZftUOI9OJ6vYi13n7syP6vpIHSb5-AhuvUUC9FjFuxQxy7HQdEU3aAMxixSiQqPH65kZk/s1600/PK5_4241-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_ucGM8vC2MOGMWFaLaLqQ62eGw1kf3mjhK8pPlpfvaqEWEycZvpxELCRu_oNPs1EYCrOg7dZftUOI9OJ6vYi13n7syP6vpIHSb5-AhuvUUC9FjFuxQxy7HQdEU3aAMxixSiQqPH65kZk/s320/PK5_4241-klein.jpg" width="320" /></a></div>Linked via a ribbon cable on the other side of the box is a male DB-25 plug.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgshrCFG-NZcHJN2AJBLxG31q5aVXSjuRa5BxDCDO9IfZXQxrrHBPUIc_95Cb0hBChUhXE2kgIPHT2l3DvYRMOKmMWHoDmm0olKhqyePKvoA5KVxhT8BO058e31mwBN1_rkpPhFHmVkoVs/s1600/PK5_4245-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="148" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgshrCFG-NZcHJN2AJBLxG31q5aVXSjuRa5BxDCDO9IfZXQxrrHBPUIc_95Cb0hBChUhXE2kgIPHT2l3DvYRMOKmMWHoDmm0olKhqyePKvoA5KVxhT8BO058e31mwBN1_rkpPhFHmVkoVs/s320/PK5_4245-klein.jpg" width="320" /></a></div>An obvious question is why a serial interface needs 25 pins (and 25 wires connecting them). The answer lies in the fact that the standard contains some wonderful bells and whistles, such as the ability to communicate via a secondary serial channel without interrupting the communication taking place via the primary serial link.<br />
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Industry soon responded to this extravagance by ignoring most of the 'unnecessary' pins, and replacing the DB-25 plug and socket with a DB-9 plug and socket. This illustrates just one way in which vendors used their own versions of standards. (Also, technically, it was a DE-9, but everybody called it a DB-9.)<br />
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The breakout box, however, supports all 25 connections. Three banks of eight DIP switches enable one to make or break the corresponding connection. Line 1, <i>protective ground</i>, is permanently connected - the connection status of the remaining 24 depends on the setting of a DIP switch.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWz2IbMT_aUFLyF18ItoE96Pi9c822qBOwMjPZplnCzeJgUBM86XINbP9IoYQKnyUEm7tQh2FudPJKr0ZXJRrL9iF3TwT-eJs3RmX4Jlwb5BngvXO0mfvYEVSgqweTuxHVmfzShLZMsWk/s1600/PK5_4258-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWz2IbMT_aUFLyF18ItoE96Pi9c822qBOwMjPZplnCzeJgUBM86XINbP9IoYQKnyUEm7tQh2FudPJKr0ZXJRrL9iF3TwT-eJs3RmX4Jlwb5BngvXO0mfvYEVSgqweTuxHVmfzShLZMsWk/s320/PK5_4258-klein.jpg" width="320" /></a></div>Only the most important lines are wired through a LED. The electrical specification of RS-232 states that about -15 volt indicates a 1 and about +15 volt a 0. (In fact, anything below -3V indicates a 1, and anything above +3V a 0.) The LEDs on this particular breakout box glow green for a negative voltage (1) and red for a positive voltage (0).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi6rguM_aMbruDF84vqv3Sj_9uGMaz_VOyx-M4DPX9PUWWBBMl8d1xCaMBWgvhOiN6XMFAd2nqcPz51Bd9W2Wq70-1JRAXYAeWzqNGbt7QcJE5H_TUHSY_cOU6G-491ns7dotpwoizTm94/s1600/PK5_4253-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi6rguM_aMbruDF84vqv3Sj_9uGMaz_VOyx-M4DPX9PUWWBBMl8d1xCaMBWgvhOiN6XMFAd2nqcPz51Bd9W2Wq70-1JRAXYAeWzqNGbt7QcJE5H_TUHSY_cOU6G-491ns7dotpwoizTm94/s320/PK5_4253-klein.jpg" width="320" /></a></div><br />
The functions of the various pins of the interface are listed in the lid of the unit for ease of reference. (This is the essence of the functional specification of RS-232-C.)<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX6kS4LkuFpJx0Owx69CNzCRpF2U0-XVIDr4Lw7uRvUOM1r7ntyNfOeGzy7KVVgRCovtywiTm2zsbAXjYJPJgHYBBOhmJO0aT1Dby5fT5qZBvkrIQQMwfBl_T5ewg-pic1I4wrzWXSYYI/s1600/PK5_4247-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="301" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX6kS4LkuFpJx0Owx69CNzCRpF2U0-XVIDr4Lw7uRvUOM1r7ntyNfOeGzy7KVVgRCovtywiTm2zsbAXjYJPJgHYBBOhmJO0aT1Dby5fT5qZBvkrIQQMwfBl_T5ewg-pic1I4wrzWXSYYI/s320/PK5_4247-klein.jpg" width="320" /></a></div>The picture above (when enlarged) not only lists the names of the pins, but also identifies the direction of the signal. The two endpoints are labelled DTE and DCE. DTE is an abbreviation for <i>data terminal equipment</i>. The DTE may be a dumb terminal, but in most interesting applications the 'terminal' is really a computer. DCE used to indicate <i>data communications equipment</i>, such as modems. However, it was changed to stand for <i>data circuit-terminating equipment</i> - that is, it referred to the sort of thing that one would attach to the end of the telecommunications company's circuit, such as a modem.<br />
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One needs one further historical note to fully appreciate the specification: in the very old days modems were referred to as <i>datasets</i>. Therefore line 6 (DSR, <i>data set ready</i>) in modern language would have been called <i>modem ready</i> or something similar.<br />
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To consider the (procedural) operation of the interface assume a DTE (such as a PC) wants to send a byte to a DCE (such as a modem). The DTE uses line 20 (DTR, <i>data terminal ready</i>) to signal the DCE that it is ready. The DCE uses line 6 (DSR, <i>data set ready</i>) to indicate to the DTR that it too is ready. The DTR then raises RTS (<i>request to send</i>). If the DCE agrees, it raises CTS (<i>clear to send</i>). The bits making up the byte are then transmitted via TD (<i>transmitted data</i>). Note that there is not an equivalent set of signals to transmit data from the DCE to the DTE: the DCE raises CD (<i>carrier detect</i>) when it sees data arriving on the phone line at the other end of the modem. Without waiting for permission, the DCE then sends the data to the DTE via RD (<i>received data</i>).<br />
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Of course this asymmetry causes problems when one wants to connect two identical devices (such as two PCs). Problems also exist when devices do not fully support the standard. In the picture below pins 6 and 20 on the DTE side are jumpered. Therefore the moment the DTE says it is ready via line 20 (DTR) it gets a 'confirmation' (its own signal) via pin 6 (DSR), making it believe that the DCE is ready. Similarly one may jumper RTS and CTS together so that a <i>request to send</i> will lead to an immediate <i>clear to send</i>, without even involving the DCE. These are the type of tricks one would use to get a DCE to accept data even if it was not able to signal its own readiness to receive data.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgs3lXWuvpQMo9J-zy_rMN2QPItGvBrttU5tENpDHkX4K_y9VQqudPCGRba3yT_Zh-zXlnmlYhUWSl8tI1FZ7cePREnMcmI8o7tz2M_tTCZwfSU23ilHskjbadfmrElNg4ZKRS4VgVFPqw/s1600/PK5_4246-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="222" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgs3lXWuvpQMo9J-zy_rMN2QPItGvBrttU5tENpDHkX4K_y9VQqudPCGRba3yT_Zh-zXlnmlYhUWSl8tI1FZ7cePREnMcmI8o7tz2M_tTCZwfSU23ilHskjbadfmrElNg4ZKRS4VgVFPqw/s320/PK5_4246-klein.jpg" width="320" /></a></div><br />
One particular serial cable that was quite popular was the so called <i>null modem </i>- a serial cable used to connect two computers (or, in general, two DTEs). RD on one plug would be connected to TD on the other, and vice versa. The DTR is connected to DSR and CD on the other end: when this PC wants to transmit, it raises DTR, and the other PC thinks that the 'modem' is ready, <i>and</i> that data is arriving via it. (Similarly DTR on that end is connected to DSR and CD on this side). Finally, one could jumper RTS and CTS together on each side, so that either side can give itself permission to send. If this did not work (and it often did not) then it was time to reach for the breakout box. I remember a time when I had to connect a Univac 1100 mainframe to a Burroughs B20 micro via a serial cable. No matter what I did, I was unable to push communication speed above 300bps. And the serial interface on the mainframe cost more than what a typical car did...<br />
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Here is the breakout box with a matchstick as an indication of its size.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgno4OUlbZGrvZ8bGS2GTjQ0tnHHh0cpNQ0wAF5DRohAtfv6e72tZzVrw_wCPJ6W5CN9oGLTqekez1gEIh84imR-p0h-S5NxxDwYNjpo8nOvjzZC5xQX0BWaQB2gu46J-GTITMRiVxBF8o/s1600/PK5_4251-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgno4OUlbZGrvZ8bGS2GTjQ0tnHHh0cpNQ0wAF5DRohAtfv6e72tZzVrw_wCPJ6W5CN9oGLTqekez1gEIh84imR-p0h-S5NxxDwYNjpo8nOvjzZC5xQX0BWaQB2gu46J-GTITMRiVxBF8o/s320/PK5_4251-klein.jpg" width="320" /></a></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-15974574530990832182011-07-30T18:44:00.000+02:002011-07-30T18:44:11.987+02:00Token ring multistation access unitA physical ring topology is prone to fail when any of the nodes on the ring fail. Suppose the beads below are nodes and the string represents network links. A break at any node or any link breaks the ring.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigwe-l5c4wyxDmL9pAbeZCZxCMzFySICXjd5UcEsrP16ndmGw3uRDlBrpQ3Chr8wikpsXvL16_EcHlKf5vcFdCERaM_fitDJ33d5_4vC_83OHUtIpBwJkEIZaXyy3Lf2Q2NXbF0ARXNbM/s1600/PK5_4232-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigwe-l5c4wyxDmL9pAbeZCZxCMzFySICXjd5UcEsrP16ndmGw3uRDlBrpQ3Chr8wikpsXvL16_EcHlKf5vcFdCERaM_fitDJ33d5_4vC_83OHUtIpBwJkEIZaXyy3Lf2Q2NXbF0ARXNbM/s320/PK5_4232-klein.jpg" width="320" /></a></div>The solution is to wire all nodes on the ring via a central 'hub' that bypasses any node that is not responsive or not present. Below the nodes are linked though such a hub.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjw8ULoFBfL5PgL7ilTy0zldBz3e2bcXuE896dsaRmuDlXeHTF-UOvHbuB7uyxKushwGE3uDe1CVsMC08-ZvBtxQeKXk_7z_I-0Uuerhxyb_MHhrAz8-rX8Ir1wD0Ik_n0CxBKToPt-xwE/s1600/PK5_4228-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjw8ULoFBfL5PgL7ilTy0zldBz3e2bcXuE896dsaRmuDlXeHTF-UOvHbuB7uyxKushwGE3uDe1CVsMC08-ZvBtxQeKXk_7z_I-0Uuerhxyb_MHhrAz8-rX8Ir1wD0Ik_n0CxBKToPt-xwE/s320/PK5_4228-klein.jpg" width="320" /></a></div>If a node becomes unresponsive, the hub simply bypasses that node and the ring remains a ring.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0SZeZojWcatFnGFnC8UeJHRvAnSRviXzYpHRRlP12o9SIHIYiX8xESZWaECaH7tUoq3di2q2he9cy_-2rJFC6DwVNiNYXnf2YeFrgEF3mKtg1VHNg7dhB4kKzzgIp47reALVFZWRN-tU/s1600/PK5_4229-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0SZeZojWcatFnGFnC8UeJHRvAnSRviXzYpHRRlP12o9SIHIYiX8xESZWaECaH7tUoq3di2q2he9cy_-2rJFC6DwVNiNYXnf2YeFrgEF3mKtg1VHNg7dhB4kKzzgIp47reALVFZWRN-tU/s320/PK5_4229-klein.jpg" width="320" /></a></div><br />
The 'hubs' through which token ring networks are wired are known as multistation access units (MSAUs or MAUs). Below is an 8-port IBM 8228 MSAU. It can operate at either 4 or 16Mbps using the IEEE 802.5 standard. It also has RI and RO (ring-in and ring-out) ports enabling it to be connected to up to 31 other MSAUs making it possible to build a ring of up to 256 nodes. (Later MSAUs also supported 100Mbps, and plans were made to build 1Gbps MSAUs, but were abandoned before they were built.)<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhE0tJnIyeykszOTIn6YQj-LOxhtyRQq-1wIanFcnVJ1wuOcmewBretHXSPMHCCjUe8IOOBq6h36To0WC1iCeN349NL1vma_yPaZTOaSVUfdlwaHdodhzO5DpwAygii8JdeQbzEvcjM6Ss/s1600/PK5_4219-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="180" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhE0tJnIyeykszOTIn6YQj-LOxhtyRQq-1wIanFcnVJ1wuOcmewBretHXSPMHCCjUe8IOOBq6h36To0WC1iCeN349NL1vma_yPaZTOaSVUfdlwaHdodhzO5DpwAygii8JdeQbzEvcjM6Ss/s320/PK5_4219-klein.jpg" width="320" /></a></div><br />
The ports on the IBM 8228 use the IBM Data Connectors (IDCs).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjombXKcXC05PiflVN0gwP4glC3UK_FpeEYV-4NzpPr7zIXfQFuriij42WSXdscojQkC_pG663B5wywoAmabNUih357OP1p9dyAfIg7pYchv7pJTnVJ9Dc3yEVHXqWJeqMIY71Nxn5TWsg/s1600/PK5_4221-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="223" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjombXKcXC05PiflVN0gwP4glC3UK_FpeEYV-4NzpPr7zIXfQFuriij42WSXdscojQkC_pG663B5wywoAmabNUih357OP1p9dyAfIg7pYchv7pJTnVJ9Dc3yEVHXqWJeqMIY71Nxn5TWsg/s320/PK5_4221-klein.jpg" width="320" /></a></div>The connectors are interesting because the 'plug' and the 'socket' are identical. For this reason the data connectors are often called <i>hermaphroditic</i>. As one may observe in connector number 7 above, two pairs of copper strips are exposed in the middle - one for sending and one for receiving. To plug another connector onto this one it would be turned by 180°. The transmission pair of the one would automatically mate with the receiving pair of the other and vice versa.<br />
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The next picture shows two cables that are about to be plugged into one another.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhryOy3YX7IevMYczc2EoYecKxA4Lz4r35SnjsmPC2nTMcDajPft7n512eAPDxtnvsLCrTJ7tNayv4-_KXgcoREOxPWwaTMLqoFUkoXgHJSO1DwJt1Yci6ShClDMNhth3v_rn3ZB6Uzgck/s1600/PK5_4224-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhryOy3YX7IevMYczc2EoYecKxA4Lz4r35SnjsmPC2nTMcDajPft7n512eAPDxtnvsLCrTJ7tNayv4-_KXgcoREOxPWwaTMLqoFUkoXgHJSO1DwJt1Yci6ShClDMNhth3v_rn3ZB6Uzgck/s320/PK5_4224-klein.jpg" width="145" /></a></div>And voila! The two become one.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipTYDP0dTPcTDZPEv5AdU4nW2QruRJjVjq0NiXeUEugEIXuujuFGWboiA2SQQBjQ1e_asuhwQ3kfSZ6BPT4BrTT-bSrrX6fYgXalB_gTRmPiakYu9USGn7436dx8XqdF_hb9cnuCTRgAA/s1600/PK5_4225-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipTYDP0dTPcTDZPEv5AdU4nW2QruRJjVjq0NiXeUEugEIXuujuFGWboiA2SQQBjQ1e_asuhwQ3kfSZ6BPT4BrTT-bSrrX6fYgXalB_gTRmPiakYu9USGn7436dx8XqdF_hb9cnuCTRgAA/s320/PK5_4225-klein.jpg" width="156" /></a></div><br />
An aspect of the connectors that may not be clear in the post thus far is their size. The MSAU is intended to be built into a 19" cabinet. Each connector measures about 25mm x 25mm x 40mm. That is huge!<br />
<br />
Here is the MSAU with the 18" (45cm) ruler from earlier posts.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSr1VWTMVFIPHaskXgUMNcOQyi62gy8uz-SJspbt8ERnm-xuwuI0YuiRyGjKjwIKRPY9zZ2P4f6RSeoNNT9Dhm7cvIzIOt_ULi4C751vdJxEF_t3dCdLSm6JGECkb6MC-a7h3vxth9nAw/s1600/PK5_4222-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="161" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSr1VWTMVFIPHaskXgUMNcOQyi62gy8uz-SJspbt8ERnm-xuwuI0YuiRyGjKjwIKRPY9zZ2P4f6RSeoNNT9Dhm7cvIzIOt_ULi4C751vdJxEF_t3dCdLSm6JGECkb6MC-a7h3vxth9nAw/s320/PK5_4222-klein.jpg" width="320" /></a></div><br />
The IBM 8228 MSAU was shipped with eight baluns that converted the IDC to an RJ-45 socket. Baluns, however, will be the topic of a future post.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-33622828998793810032011-07-24T12:25:00.000+02:002011-07-24T12:25:36.462+02:00Sun JavaStationIn the second half of the 1990s a few vendors had a dream: Let's build a computer where the operating system, applications and data are somewhere on the network. IBM succinctly described the dream in in the manual of its Network Station 300.<br />
<blockquote>"The Network Station Series 300 is designed for environments that combine a need for multiple server access with browser access to applications and data that reside on a corporate intranet or the Internet. ... [It] can be thought of as the 'Internet computer'."</blockquote>(IBM's Network Station will be featured later in this museum.)<br />
<br />
These computers were known as network computers - a phrase still trademarked by one of the vendors.<br />
<br />
Sun's contribution was the JavaStation - or the JavaStation NC (where NC indicates that it is a network computer). The first JavaStation version looked like a brick. The second (and 'real') version of the JavaSation had a much more futuristic appearance.<br />
<div class="separator" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyXqf1uQX0VEyHJ29DV9-pxj5p9I-GLZfY5oRo-dgJrcbX-ngrPxJCQrmqm5Is10rTsVDJS5ZpGSNUarM4ViOPfWHyCL35Nbo7SJOnlJlEWxbWo5fBAZs4_y13egNV77KlH0RXZf6fRuY/s1600/PK5_2035-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyXqf1uQX0VEyHJ29DV9-pxj5p9I-GLZfY5oRo-dgJrcbX-ngrPxJCQrmqm5Is10rTsVDJS5ZpGSNUarM4ViOPfWHyCL35Nbo7SJOnlJlEWxbWo5fBAZs4_y13egNV77KlH0RXZf6fRuY/s320/PK5_2035-klein.jpg" style="cursor: move;" width="320" /></a></div>On the technical side the major innovation of the second version was the ability to operate outside the context of an intranet. It could boot on its own, and then use applications, data and other services from the Internet, without any 'local' facilities.<br />
<div class="separator" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMAUt4qAi9K-baS6nBlvql8P1NeQNpuwZxsbFEuW1_UFXiJuMxXUjw0MfpK_ZMISQT5AG9lx-SfrDKRoAaFApxDcExGT7U_NQjHSYh9RoCrRjoS1L6qpIeTo91Wnih3TdssJMNBJV3tos/s1600/PK5_2043-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="229" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMAUt4qAi9K-baS6nBlvql8P1NeQNpuwZxsbFEuW1_UFXiJuMxXUjw0MfpK_ZMISQT5AG9lx-SfrDKRoAaFApxDcExGT7U_NQjHSYh9RoCrRjoS1L6qpIeTo91Wnih3TdssJMNBJV3tos/s320/PK5_2043-klein.jpg" style="cursor: move;" width="320" /></a></div><div style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px;">On the outside there is hardly any indication of the intended use of the JavaStation. Two 'doors' at the rear reveals something more about its intended use.</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGCMcX_ejPb-Ka9ahmrLL9XufV5-bEkTQCRRD773ghbBRZvQYmCDe2uYNVIwtKTX_jMePWIHZ4iRUCK-W3n3i388XZrol9wAh67atje5hNcuVFsFxFabacFG0hYksXnW4JByNLrnoz92w/s1600/PK5_2040-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGCMcX_ejPb-Ka9ahmrLL9XufV5-bEkTQCRRD773ghbBRZvQYmCDe2uYNVIwtKTX_jMePWIHZ4iRUCK-W3n3i388XZrol9wAh67atje5hNcuVFsFxFabacFG0hYksXnW4JByNLrnoz92w/s320/PK5_2040-klein.jpg" width="267" /></a></div>The key connector is the RJ-45 socket that enables it to be connected to the network. Provision is also made for a (PS/2) keyboard, a (PS/2) mouse, microphone, speakers and a serial connection (and, of course, electricity).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWNXfxcltPZH6U9R3CW49PT6MLaEIIrrlh4l3d33zaG-pFIAoV0PIEjFmdUCOgyqjuXLnVraUWlgrE8CG6WZUS-jeKzXETO6u9vujbe_zOmYS_wS5XhslGxjK2ThMsiyT_Yf7_wUUjL20/s1600/PK5_2041-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWNXfxcltPZH6U9R3CW49PT6MLaEIIrrlh4l3d33zaG-pFIAoV0PIEjFmdUCOgyqjuXLnVraUWlgrE8CG6WZUS-jeKzXETO6u9vujbe_zOmYS_wS5XhslGxjK2ThMsiyT_Yf7_wUUjL20/s320/PK5_2041-klein.jpg" width="198" /></a></div><br />
In order to estimate the size of the JavaStation it is pictured below with a matchstick.<br />
<div class="separator" style="clear: both; margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0px; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrDqnPGjSRZ7MhcXcHbQN_Eb1EZzerLhGk-YrK9oobTeTN5KlWUhaLh4xzqAT3LiPe2TxbApChxMwymoV3ShfEPZtDuoKiSK6d3NN9rh1rmeIjZQ114RTby4dAN10I-u-mIvLeZooNYqo/s1600/PK5_2048-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgrDqnPGjSRZ7MhcXcHbQN_Eb1EZzerLhGk-YrK9oobTeTN5KlWUhaLh4xzqAT3LiPe2TxbApChxMwymoV3ShfEPZtDuoKiSK6d3NN9rh1rmeIjZQ114RTby4dAN10I-u-mIvLeZooNYqo/s320/PK5_2048-klein.jpg" style="cursor: move;" width="229" /></a></div><div>On the inside it has a (fast for the time) 100Mhz MicroSPARC IIep CPU and provision for up to 64MB of RAM.</div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-41433012816414323182011-07-09T00:06:00.000+02:002011-07-09T00:06:51.116+02:00ISDN 'modems'In order to connect one's network to the outside world via <a href="http://www.networkmuseum.net/2011/07/isdn-bri.html">ISDN BRI</a> one needs some device to do so. In an <a href="http://www.networkmuseum.net/2011/07/isdn-bri.html">earlier post</a> it was explained that the NT1 terminates the telco's network and 'converts' it to an S/T bus. Now we need devices to plug into that bus.<br />
<br />
In general the lines coming into a company are plugged into some networking device, such as a router. A medium-sized company may, for example, have lines coming in from various offices - they may run a copper cable to their building next-door, have leased lines to their bigger branch offices and then use (or have used) ISDN to connect to a number of their smaller offices. This means their router (or other network device) has to be able to connect to a range of possible media. And nobody wants to replace an expensive piece of technology the moment other technology changes - for example replacing the ISDN line to the telco with an optical fibre to the ISP should not require a new router. The solution was obvious: put the interface to the media on an interface card that could be replaced when necessary. We have seen such solutions in mainframes, minicomputers and personal computers. A number of products that are currently being built ignore that lesson - they are engineered for obsolescence because often the battery is built into the unit. When the battery dies, so does the unit. The unit will not survive until new technology comes along.<br />
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But, back to interface cards. The card below provides an ISDN interface for a range of Cisco routers. It is a Cisco ISDN BRI S/T 1 port module for the 17XX / 26XX / 36XX series routers. As the S/T indicates, it is intended to be plugged into the S/T bus (or the S/T bus into it?). In most contexts one would simply take an appropriate cable with two RJ-45 plugs on each end, and plug the one end into the NT1 and the other end into this interface card.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZtK_5olwF6S_k_RlEgsdc5BikO7cJt7YRBe57oRERh90dLC8q80Y1bLtrQvGoQOVurhQ0dF607_aDfTpB6QwAbAcWx3w9bBDBWMolS4aaohQ2KJ_DgXz4TtVFNDN1ccHXM2wnQZvBmnM/s1600/PK5_2029-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="227" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZtK_5olwF6S_k_RlEgsdc5BikO7cJt7YRBe57oRERh90dLC8q80Y1bLtrQvGoQOVurhQ0dF607_aDfTpB6QwAbAcWx3w9bBDBWMolS4aaohQ2KJ_DgXz4TtVFNDN1ccHXM2wnQZvBmnM/s320/PK5_2029-klein.jpg" width="320" /></a></div>In the picture, the S/T socket is clearly labelled as such. There are three tiny lights behind the holes in the cover plate. Those holes are labelled B1, B2 and OK. Obviously the OK light glows if the interface card operates correctly, and the B1 and B2 lights indicate activity on each of the two B channels.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgt8-uEQkwR1rwN0xs4XNQRv8nkV6-2532YcgieE0WZ3d73Oi-IZkOyKKJniZ4PhKBcyu3U6pwwql4SOHt0CFhsWmKe7EvWps9joYW1tUZo4PymTG5SAG810TNw4W35h4NyD2aUNSLR3LU/s1600/PK5_2030-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="179" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgt8-uEQkwR1rwN0xs4XNQRv8nkV6-2532YcgieE0WZ3d73Oi-IZkOyKKJniZ4PhKBcyu3U6pwwql4SOHt0CFhsWmKe7EvWps9joYW1tUZo4PymTG5SAG810TNw4W35h4NyD2aUNSLR3LU/s320/PK5_2030-klein.jpg" width="320" /></a></div><br />
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This particular module is the Cisco WIC-1B S/T. <i>WIC</i> is an abbreviation for WAN interface card. The intention is to feature several others WICs on this site at a later stage.<br />
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The word 'modem' was placed in quotation marks above because one normally uses a modem to connect to a telephone line and ISDN BRI is, in some sense, a glorified telephone line. However, where normal telephone lines use analog signals, ISDN uses digital signals and the role of the ISDN WIC would be to provide a digital-to-digital connection. Some conversion may be required, but it is not modulation or demodulation, and calling this WIC a modem would therefore be incorrect.<br />
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However, the following product is a bit harder to classify. Whereas the medium to big enterprise may use a Cisco (or Nortel, or other) router, the small office or home office only wants to plug a few devices into its ISDN line. So, let's look at a US Robotics Courier ISDN modem (omitting the quotation marks around 'modem' while we are making our minds up whether it is indeed a modem).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEin8MZfZHRxRnUzOvPb_Wp70jkoBaxIlCabyERSJHxFEpIZx4JhICngIdpCMUo5XavrK9IIMWim6qAi9B1n5zuThTX43Y8phXNW4IDryApThMZYdIvJdpEFuKz78FReFnEjKEu7DhM18XU/s1600/pk5_2021-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="244" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEin8MZfZHRxRnUzOvPb_Wp70jkoBaxIlCabyERSJHxFEpIZx4JhICngIdpCMUo5XavrK9IIMWim6qAi9B1n5zuThTX43Y8phXNW4IDryApThMZYdIvJdpEFuKz78FReFnEjKEu7DhM18XU/s320/pk5_2021-klein.jpg" width="320" /></a></div>At the very least, the word <i>modem</i> appears clearly on the faceplate of this piece of equipment. Some readers may also recognise the <i>V.34</i>, which refers to an old analogue modem standard.<br />
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Let's look at the rear of the unit in an attempt to figure out what is going on.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaWZpdb0cRjNeJgUxhEH7CUleqpPEM6RWlrif7d5E29Z_TMuDCwnaQUUGYBsPSLnYDLhOlXMtU9RK1MwA2aqO-M3cTbQ6yG_pC8ldRWZqIylfrITY5EzcQlbm8EItnvtrAkqRRuv34F5I/s1600/PK5_2023-klein2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="236" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaWZpdb0cRjNeJgUxhEH7CUleqpPEM6RWlrif7d5E29Z_TMuDCwnaQUUGYBsPSLnYDLhOlXMtU9RK1MwA2aqO-M3cTbQ6yG_pC8ldRWZqIylfrITY5EzcQlbm8EItnvtrAkqRRuv34F5I/s320/PK5_2023-klein2.jpg" width="320" /></a></div><br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdfqLx6pMVOcOWDN3_xnvoHtQx_F90pnOQMWzOkAExtzlkIRRjY_O9Llqfx-WlxXKY4nVD8_txB2hTBvbF-G95jlGe4H9eqXcJMDWuTPddGUIxqukFNYotCkrOnmAd9SYIbvtZMdl4c-A/s1600/PK5_2023-klein3.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="97" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdfqLx6pMVOcOWDN3_xnvoHtQx_F90pnOQMWzOkAExtzlkIRRjY_O9Llqfx-WlxXKY4nVD8_txB2hTBvbF-G95jlGe4H9eqXcJMDWuTPddGUIxqukFNYotCkrOnmAd9SYIbvtZMdl4c-A/s320/PK5_2023-klein3.jpg" width="320" /></a></div>The reader should immediately notice the S/T socket. This is where it will be connected to the S/T socket on the NT1. To the left is a fancy socket for the power adapter, which we may ignore. Then there are two more interesting sockets: an RJ-11 socket labelled phone and a DB-25 female plug labelled data.<br />
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The RJ-11 socket is intended for an ordinary old-style analogue telephone. This unit will convert the analogue signals from the phone to digital signals before sending them out on the S/T bus, and it will convert digital signals arriving on the S/T bus to analogue signals that will be audible as normal speech on the analogue phone. For this the unit acts in reverse when compared to a normal modem, where digital signals are converted to analogue signals to go out on the phone line. Here the analogue signals of the phone are converted to digital to go out on the digital phone line and vice versa. Does that mean we may call the unit a modem (or is it perhaps a <i>demod</i>)?<br />
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As usual there are complications. The telco is really now providing two networks: one analogue and one digital. If you use your fancy ISDN modem to phone someone who is still using the plain old telephone system (POTS) you are sending out digital signals on a digital network and they are waiting for analogue signals on an analogue system. So, somewhere the telco has to interface its digital network to its analogue network and if it sees digital telehone data coming along an ISDN B channel it has to convert it to analogue before placing it on the analogue network, and vice versa. Of course if you are calling someone who has a digital phone on the ISDN network (or who has a similar setup than you) that phone (or the modem there) will 'understand' the digital signals and interpret them correctly without any further involvement from the telco.,<br />
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Let's now move our attention to the DB-25 female plug labelled <i>data.</i> This is a serial (or RS-232-C) connection. For the modern reader, an RS-232-C interface is almost like a modern USB or FireWire interface; it's just much slower and much more fiddly. Of course this is where the computer is plugged in. It provides a digital connection between the computer and the modem, so it seems most of our problems disappear. Digital-to-digital is usually simple - we may have to rearrange the bits a bit, add some overhead bits and so on, but it all really amounts to repackaging . Again life is not that simple. It is possible that the party you are communicating with also uses an ISDN line, in which case most of our problems are indeed solved. It's digital to digital to digital - via RS-232-C, then via the ST bus, then via the U loop, then via the telco's ISDN infrastructure, then via a U loop again, via another S/T bus, an RS-232-C link and we are at our destination!<br />
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However, suppose you want to communicate with a poor soul who is still using an analogue modem on the POTS. There seem to be two possibilities. The one is that you use the telephone plug - convert your digital data to analogue, send it into the phone interface that will convert it to digital immediately, transmit the digital data to the bridge between the telco's analogue and digital networks, where it will be converted to analogue again - until it reaches the destination modem, and where it will be converted to digital again for consumption by the destination computer. If this sounds a bit cumbersome (and error prone) it does because it is. A better solution would be to keep the data in digital format as it travels from the computer, along the ISDN line, until it gets to the point where it hops over to the POTS network. At this point we have no choice - the data has to be modulated to analogue - but it only has to happen once which is a significant improvement. However, the rate at which data can be carried along an analogue phone line is slower than the 64kbp (and much slower than 128kbps) of ISDN. So, if we want to use this option we have to tell our ISDN to limit speeds that can go over to an analogue network.<br />
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To discuss the matter further would require a detailed discussion of the rather complex configuration of the modem. Amongst others it entails telling the data channel what the maximum speed it is allowed to use if it will connect to an analogue modem on the other end. And it entails configuring the analogue B channel such that it knows whether is gets voice or data (or fax) inputs. The interested reader will find the modem's manual online. After working through that documentation the reader should be able to answer the question whether this is a real modem or not.<br />
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<div style="text-align: center;">-o0o-</div><br />
Let's return to the WIC. As noted, the user of the router can in principle replace the WIC with any other WIC. So, if the user wishes to start using ADSL rather than ISDN BRI, the ISDN WIC can be pulled out and replaced with an ADSL WIC. Of course this means the user has to ask the telco to convert its line to an ADSL line. ADSL will have to wait for a later post. In the meantime, here is an example of an ADSL WIC.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSkbb0L3Jfcwa4tZGuJnvhFp2PdLD0zMVOvHhSrwFmKjV3QRWlInIQAWnSrOPqZgV751uT6NNfujWSghwvkfap2ag2k2ZYSYGPavRh63WFbK5qt0BYQr0HhcFo67YkE7pr8GUsUAaDLuA/s1600/PK5_2031-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="223" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSkbb0L3Jfcwa4tZGuJnvhFp2PdLD0zMVOvHhSrwFmKjV3QRWlInIQAWnSrOPqZgV751uT6NNfujWSghwvkfap2ag2k2ZYSYGPavRh63WFbK5qt0BYQr0HhcFo67YkE7pr8GUsUAaDLuA/s320/PK5_2031-klein.jpg" width="320" /></a></div><br />
Side by side one can see that the two WICs look rather similar. The ADSL one uses an RJ-11 plug - like normal phones do, while the ISDN uses an RJ-45. Other than that the status indicators are different (and the placement of the socket obviously differs).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjph8IAfRikX1AxmrDw65waRaZSKfDWb2r9ROLddUWMZSGe2w_hQLVatTVjRCXfrHl-6O3F7LeVYo7kHk7pkQSy10-v9zgLVeHUB0pmgvOUlH4qWojRrT2LcbTgEOx9nEw47nE4CS92RvE/s1600/PK5_2032-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="99" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjph8IAfRikX1AxmrDw65waRaZSKfDWb2r9ROLddUWMZSGe2w_hQLVatTVjRCXfrHl-6O3F7LeVYo7kHk7pkQSy10-v9zgLVeHUB0pmgvOUlH4qWojRrT2LcbTgEOx9nEw47nE4CS92RvE/s320/PK5_2032-klein.jpg" width="320" /></a></div><br />
To conclude, here are the three devices featured in this post together (and two matchsticks have been added so indicate size).<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpC3DEHtP-LFUJdVTrZ7u5KZ0lzuy1w5mUHIu2iAqlE-EpkMeHFD10-weKuKz9mK3FQ07RLXkXlpHznBX2MuAMUu2sy47IB9WtSpJ_gX7ls4BDRiULWFsGFGTDkDwjfgwxGU77A0iJg8k/s1600/PK5_2033-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpC3DEHtP-LFUJdVTrZ7u5KZ0lzuy1w5mUHIu2iAqlE-EpkMeHFD10-weKuKz9mK3FQ07RLXkXlpHznBX2MuAMUu2sy47IB9WtSpJ_gX7ls4BDRiULWFsGFGTDkDwjfgwxGU77A0iJg8k/s320/PK5_2033-klein.jpg" width="320" /></a></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-45707336209980115642011-07-05T09:50:00.000+02:002011-07-05T09:50:28.203+02:00Roaming costs<div style="text-align: center;">This is the front page of the Financial Times (Europe) of 4 July 2011:</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2YH2Y2uCNy7SbNZk3d9qS2_zGvsJxvoKCppknoxqIWprND0qrvLKcq4XGR0Nfjs4h819_nTz8XOniwL_yomIna-SRnqaPJzzoLH3AT99oQJIxA46z0VgNgxK33VMGnDFuBDAtmqUUHrU/s1600/P1000115-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2YH2Y2uCNy7SbNZk3d9qS2_zGvsJxvoKCppknoxqIWprND0qrvLKcq4XGR0Nfjs4h819_nTz8XOniwL_yomIna-SRnqaPJzzoLH3AT99oQJIxA46z0VgNgxK33VMGnDFuBDAtmqUUHrU/s320/P1000115-klein.jpg" width="274" /></a></div><br />
<div style="text-align: center;">The crux of the headline story is:</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWSuUaQ_FNQfkVNWotvOgfb2l55DD08KhkSgxyiYsWywULsIhY7heeL9abXq4SlsQL-AXBKB2k0iMIOpWg5KciIG8m3nOqGaBNdXHAjSUysJlTq351O7JPdg5ta67YVKqC1gt_ve5o8Hc/s1600/P1000109-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWSuUaQ_FNQfkVNWotvOgfb2l55DD08KhkSgxyiYsWywULsIhY7heeL9abXq4SlsQL-AXBKB2k0iMIOpWg5KciIG8m3nOqGaBNdXHAjSUysJlTq351O7JPdg5ta67YVKqC1gt_ve5o8Hc/s320/P1000109-klein.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"></div><br />
<div style="text-align: center;">Visually, at the prevailing exchange rate, this means:</div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFKOiB-hmcJ79UUEpY3do893K9yQznb5ihyphenhyphenrVSgAowlPQ41V3FgpqA5sA-_AfgfM8pAjvHvIaaBmKlVlvLd4IWi8bljWMkBISK8qCaVE2bSaJ3KDn695-XCpaTAKES5967T3WEV9DjkUg/s1600/P1000113-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="165" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFKOiB-hmcJ79UUEpY3do893K9yQznb5ihyphenhyphenrVSgAowlPQ41V3FgpqA5sA-_AfgfM8pAjvHvIaaBmKlVlvLd4IWi8bljWMkBISK8qCaVE2bSaJ3KDn695-XCpaTAKES5967T3WEV9DjkUg/s320/P1000113-klein.jpg" width="320" /></a></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-14959035412443350382011-07-05T07:51:00.000+02:002011-07-05T07:51:11.442+02:00ISDN BRIIntegrated Services Digital Network (ISDN) - as the name indicates - is a digital network (provided by telecommunications companies) that may be used for various (integrated) services. The services that may be 'integrated' in this manner include (voice) telephony, fax, (computer) data and anything else that may be represented as 1s and 0s. ISDN comes in two flavours: Basic Rate Interface (BRI) and Primary Rate Interface (PRI). PRI will take a E1 (or T1) line at one end and split it into 30 (or 23) 'data' channels. BRI will take a more-or-less normal telephone cable and split it into two 'data' channels. BRI is the topic of this post.<br />
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Below is the NT1 device supplied by Telkom if one had a BRI ISDN line installed at one's home or one's office. (There was an alternative device that will be mentioned in a later post.)<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7zRA41DyFS1TX-7gXF6QkQv-VEjzl7jXVO-v7cy2oNTJYY_6qfCkxOLo5x1lqUcturBZZZ2zvkDM5tSnuyX4wJuvIBSGEHGeL_hn1iSO6kQuy1QmCtqOCD7FbgqheTBZHq3036fipvkc/s1600/PK5_9451-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7zRA41DyFS1TX-7gXF6QkQv-VEjzl7jXVO-v7cy2oNTJYY_6qfCkxOLo5x1lqUcturBZZZ2zvkDM5tSnuyX4wJuvIBSGEHGeL_hn1iSO6kQuy1QmCtqOCD7FbgqheTBZHq3036fipvkc/s320/PK5_9451-klein.jpg" width="246" /></a></div>Note that this NT1 device is not an "ISDN modem" - those will be discussed in a later post (to the extent that they exist). The NT1 is the network terminator installed in one's house or office. It used to be part of Telkom's network and thus belonged to Telkom. The user's equipment could be plugged into the other side of the NT1.<br />
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Opening the NT1 provides more colour, but not more insight into its operation.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQvbKbwX4vdQte994651BEwjP56FqIWhbJ1D4rPFqHqJzesKLcq9F80eDp_aAa-rUBS4y8nZNVUc4oCZaHHGsch-pR3iFJKW5AYWLBpX6FQejEGjsKsmrGnEVxOlhWEKIfJfGRLhkzcWY/s1600/PK5_9449-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="233" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQvbKbwX4vdQte994651BEwjP56FqIWhbJ1D4rPFqHqJzesKLcq9F80eDp_aAa-rUBS4y8nZNVUc4oCZaHHGsch-pR3iFJKW5AYWLBpX6FQejEGjsKsmrGnEVxOlhWEKIfJfGRLhkzcWY/s320/PK5_9449-klein.jpg" width="320" /></a></div><br />
Let's rather look at the four sockets that are provided.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1Q_N1t6Pli4Nn7ajuvX2-YR-gZRNpKbjLhOLAUsUgNIUyV5dIeokfOHe9vbicrhenoCx54RW2gCH1TOLhg14pTK11rnKpC8fMi8m_4IcjMiTKU263W-YMhWBvJWcPtRelGwNmPYbuYCk/s1600/PK5_9452-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="172" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1Q_N1t6Pli4Nn7ajuvX2-YR-gZRNpKbjLhOLAUsUgNIUyV5dIeokfOHe9vbicrhenoCx54RW2gCH1TOLhg14pTK11rnKpC8fMi8m_4IcjMiTKU263W-YMhWBvJWcPtRelGwNmPYbuYCk/s320/PK5_9452-klein.jpg" width="320" /></a></div>On the left is the socket into which Telkom's line was plugged. This is known as the U interface. The nice thing was that one's ordinary old copper wire running from the exchange could the used. At the exchange they simply removed the link from the normal telephone system and attached it to an 'exchange' network terminator. And, at one's home the telephone was unplugged and the NT1 plugged in. Where the old telephone line could only be used for a single conversation, it now provided two data channels, either of both of which could be used simultaneously to carry data (including digitised voice from a digital telephone).<br />
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The not-so-nice consequence of this alternative use of the telephone cable was the following. Normal telephone wires supply 50 volts of electricity. Once the line was connected to the exchange network terminator 100 volts of electricity came down the line. No, it was not able to electrocute someone (because the current was limited), but it was quite capable of sending a phone or modem up in smoke. There are a couple of sad tales of people who found a 'telephone jack', unplugged whatever was plugged into it and plugged a modem in - only to immediately learn that this was no ordinary phone jack...<br />
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The next two sockets - like the U interface - are RJ-45 sockets. As noted earlier, this is where the user's equipment would be plugged in. It is easy to infer that each of those sockets would provide one of the two data channels, but such an inference would be wrong. The interface on the user's side is actually a bus (known as the S bus or S/T bus) into which multiple (more than two) devices could be plugged. Those two sockets are merely two access points to the bus. If one had more than two devices, connections to those sockets would be split to enable one to connect multiple devices.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwsJWrlonGCjKX3mg4KMwcrei4ct7yFzF4Crk40x_0piMzlhfM7AaE1c3nMvgYyGMYdzd7_JY5z7IU78KyXCmuRQiNIpgZVlMgJrSVwfuiRZowT-TefnLGPwg48s9a6y9SVzPbnY8jIL0/s1600/PK5_9453-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwsJWrlonGCjKX3mg4KMwcrei4ct7yFzF4Crk40x_0piMzlhfM7AaE1c3nMvgYyGMYdzd7_JY5z7IU78KyXCmuRQiNIpgZVlMgJrSVwfuiRZowT-TefnLGPwg48s9a6y9SVzPbnY8jIL0/s320/PK5_9453-klein.jpg" width="311" /></a></div>The observant reader may have noticed that there is a part of the cover that can be removed. Once removed it exposes some contacts and some switches. Let's ignore the switches and just look at the contacts. The upper two contacts provide an alternative to attach the NT1 to the copper cable from the telecommunications company. Rather than using a normal phone jack, the incoming line could be inserted into the top two holes. This immediately removes the temptation for anyone to plug a modem into the phone jack, because there no longer is a normal phone jack. Similarly, the bottom four holes provide an alternative attachment point for the S bus (replacing the need to use the two external RJ-45 connectors). If these connectors inside the box were used, it was typical to plug blank RJ-45 plugs into the external RJ-45 sockets.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggZqKHMRmmn5lCuCbyx9VY63g6OCtuhUP792kIRLP-aPFdlTMa10AEUh3N9w2cDEoZF8dGQOLIfX71zO3NRV5OO8M94OLLzItZkfnR6ZI1pZIDXt_MYOTALtki4ce_Z80pcdzG3cuIjE4/s1600/PK5_9454-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="177" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggZqKHMRmmn5lCuCbyx9VY63g6OCtuhUP792kIRLP-aPFdlTMa10AEUh3N9w2cDEoZF8dGQOLIfX71zO3NRV5OO8M94OLLzItZkfnR6ZI1pZIDXt_MYOTALtki4ce_Z80pcdzG3cuIjE4/s320/PK5_9454-klein.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: left;">The last remark about four points to connect the S bus may yet again lead the reader to the wrong conclusion. It is <i>not</i> the case that they provide two holes for each of the two S sockets. Looking at the picture above one may (correctly) infer that each of the RJ-45 S sockets uses four wires. Two wires are used for sending information and two wires for receiving information. Therefore the four holes seen earlier just provide access to the four lines of the S bus. They would be split as required.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">We said earlier that BRI provides two 'data channels'. Technically those channels are known as <i>bearer</i> channels, or B channels. Each B channel operates at a (guaranteed) rate of 64kbps. And then there is a control channel, known as a D channel, operating at 16kbps. BRI is therefore also often denoted as 2B+D.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">If any device on the S bus wants to communicate it would send a request via the D channel. A B channel would then be allocated to it (or, if requested, both B channels could be allocated to it providing a guaranteed 128kbps connection). If one device uses one B channel, another may use the other. Though multiple pieces of equipment could be connected to the S bus, at most two B channels could be in use at any time - and it is possible that one device could be using both. For incoming calls it was possible to let any device answer it, or, based on various schemes, to let a specific device answer the call. If one had four digital phones on the S bus it possibly did not matter who answered, but if one had a fax machine, telephone and computer connected, who answers could be important. Even when using only telephones, it could be important exactly which phone rang.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">64kbps sounds slow by today's standards. However, it should be kept in mind that the bandwidth is guaranteed. Even a megabit per second ADSL line may slow down to almost no throughput - something which is not supposed to ever happen on an ISDN line.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">We are now in a position to discuss the function of the NT1. On the one side (the U side) is a single copper loop carrying three channels (2B+D) in two directions. These six streams of data need to be multiplexed and demultiplexed by the two network terminators. In addition the NT1 has to manage the S bus: if a device puts data on the 'send' pair of the S bus, the NT1 should figure out on which channel it belongs and then multiplex it accordingly. Similarly, if data arrives from the U interface, the NT1 should figure out for which device it is intended and then send it out on the S bus with the appropriate addressing information on the receive pair of wires of the S bus.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">Just in case their is any doubt left in the reader's mind: An ordinary phone cannot be plugged into either of the S sockets. One needs a digital phone that can put the appropriate addressing information on the S bus and respond when its address appears on the S bus.</div><div class="separator" style="clear: both; text-align: left;"><br />
</div><div class="separator" style="clear: both; text-align: left;">Oh, yes - we never discussed the fourth plug. It is a normal figure-8 connector that is used to provide electricity to the NT1.</div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-65652318830657834962011-06-28T22:19:00.000+02:002011-06-28T22:19:25.211+02:00InfraredThe idea to be able to communicate without physically plugging in is an old one. A few years ago infrared was the primary technology used to achieve this. The most popular standard was one specified by the Infrared Data Association (IrDA); the acronym IrDA was often used to refer to the infrared port itself. IrDA communicated at 115kbps. A fast infrared specification (FIR) was also published that was supposed to communicate at 4Mbps. One did not encounter many FIR interfaces - and one never encountered a 4Mbps infrared link.<br />
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The problem with visually showing an infrared port is that they mostly look like black plastic. A small black rectangle on the side of a (black) notebook or cellphone does not make an interesting picture. So, here is an IrDA unit that may be installed on a personal computer to enable it to communicate with cellular phones and other portable devices with a similar interface.<br />
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As can be seen from the picture the front of this adapter indeed looks like black (reflective) plastic.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZIDCfAKCUwqyNFMpY1DWjqzVJ6yI7fgzq6GmbXjuQhLFJXG51lwcZOtS1dZflUD93Ilx8PUIEWWPSBswdT6V7cHnD435lsi2CMKcqJMhVeH3CPp8c9iDWw-aNHJOOvkq1GYMY-QP0bZI/s1600/PK5_9440-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="217" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZIDCfAKCUwqyNFMpY1DWjqzVJ6yI7fgzq6GmbXjuQhLFJXG51lwcZOtS1dZflUD93Ilx8PUIEWWPSBswdT6V7cHnD435lsi2CMKcqJMhVeH3CPp8c9iDWw-aNHJOOvkq1GYMY-QP0bZI/s320/PK5_9440-klein.jpg" width="320" /></a></div><br />
From the top it is somewhat easier to see what the unit looks like.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii0bEjSsR-w7Mnt-levd2ODuSw4eLMoO1iQ0RH1cacijmk3tUuQAjaWlUdGiVXerSq-SIUSPB1TkE0LsbBICnll9SnCOHYDVJHTqHWKfogVlr8ioIK1wrzMuxvq85gEIWnTXuVhTuzVI0/s1600/PK5_9443-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEii0bEjSsR-w7Mnt-levd2ODuSw4eLMoO1iQ0RH1cacijmk3tUuQAjaWlUdGiVXerSq-SIUSPB1TkE0LsbBICnll9SnCOHYDVJHTqHWKfogVlr8ioIK1wrzMuxvq85gEIWnTXuVhTuzVI0/s320/PK5_9443-klein.jpg" width="320" /></a></div><br />
Normally infrared light is not visible to the human eye. However, some cameras are able to record infrared light that makes it indirectly visible. The next picture was taken with such a camera while the IrDA unit was communicating. The red light on top of the unit (appearing to be orange in the picture) is a normal red light that flickers so that the user can see that the unit is operating. This red light causes some other red reflections in the translucent plastic. The important thing to notice is the light that looks purplish in the picture. This is the infrared light shining behind the translucent plastic to transmit data. As noted this light is normally invisible to humans.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwtSHFgX76P-HLlTKKW3Zgc0WuM1bp4X2SpZBDKKJw7RmDzwo2BhRuTgI_jb9HBRKhCtXKRmHCnDL8IVKnNm0elrgYdxjyVPJQO8sfob7ujgFc41MMsRZlAxmTv2rAeG8TD4B6-DVpOUA/s1600/A2841133-edited.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwtSHFgX76P-HLlTKKW3Zgc0WuM1bp4X2SpZBDKKJw7RmDzwo2BhRuTgI_jb9HBRKhCtXKRmHCnDL8IVKnNm0elrgYdxjyVPJQO8sfob7ujgFc41MMsRZlAxmTv2rAeG8TD4B6-DVpOUA/s320/A2841133-edited.jpg" width="320" /></a></div>To get two devices to communicate via infrared one would line them up so that their IrDA ports pointed towards one another and were in close proximity. (Typically they had be be closer than about 1m to each other.) And then one could request a file to be transferred or some other communication to take place.<br />
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This particular IrDA adapter was designed to plug into a DB-9 serial port. While every personal computer in the world at some point in the history had a serial port it was surprising how difficult it was to find a computer into which the IrDA adapter could be plugged to get it to light up. Later posts will say more about serial interfaces.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaWkp4mQstD_v6FC5-4K-vxNieOUtyySROpNig2u0yx26tucT5nBR2c2Ro2P8YSvo8q3obo3WHTo0-fUcr4ujpuXTYbKDamR_HHiNv-jrI_r4cxQ6jAgAG-FGoP_Zz9WJySE2vhqC8Dog/s1600/PK5_9444-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="180" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjaWkp4mQstD_v6FC5-4K-vxNieOUtyySROpNig2u0yx26tucT5nBR2c2Ro2P8YSvo8q3obo3WHTo0-fUcr4ujpuXTYbKDamR_HHiNv-jrI_r4cxQ6jAgAG-FGoP_Zz9WJySE2vhqC8Dog/s320/PK5_9444-klein.jpg" width="320" /></a></div><br />
Let's also say something about the camera used to take the infrared picture. With film cameras one can load an infrared film into any camera and take pictures (with some special considerations - for example, the point at which infrared is in focus is somewhat different from the point at which visible light is in focus, so one needs to focus at a somewhat different point than what one wants to be in focus).<br />
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In the case of digital cameras, all sensors are sensitive to infrared light. This is nice if one wants to take infrared pictures. However, the vast majority of people who take pictures, want to take a picture of the visible object and infrared light tends to enter into the picture at unexpected places and ruin the picture. Therefore most digital cameras have a filter in front of the sensor that only allows visible light to pass. Special forensic cameras are available that do not have this filter, but they are horribly expensive.<br />
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Another option is to find an old digital camera that was manufactured before these visible light filters were installed. This is the type of camera used to take the picture above. However, before saying a bit more about the particular camera it should be noted that two other options exist. One is to use a video camera without such a filter; such video cameras (often with a 'night mode') are more readily available. Finally, one may buy a modern camera and break the filter out. (Remember not to damage the sensor!)<br />
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The camera used to take the infrared picture in this post is a Kodak DCS 315. Launched in 1998, the 1.5 megapixel camera represented cutting edge technology aimed at the serious photographer. At about $5 000 (in the US) or £5 000 (in the UK) or almost R100 000 (in South Africa) it was considered a budget alternative when compared to other digital cameras at the time. As can be seen from the picture below it used a Nikon Pronea 600i body on top, with electronics added to the bottom and rear by Kodak. Normally one would use it with a hot mirror filter screwed into the front of the lens to cut out infrared light. The picture shows the camera without such a filter, because the filter was (obviously) removed to take the picture of the IrDA adapter in action. In general, most current cellphones take better pictures than this professional oldie, but cellphones still can't photograph infrared light...<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhc5sCdHn0syM1MSNcZYoJGxXjHW1qupQYlS6bNgh0aVi9F4a3dLZ1BNwODNxM17Mvh0Yum-0WtdFNTFe5DDh4AeefnWV5FwkgRIt-qovux6ycBJHCkmTerAeMVKonGQ_9IOKTIGeE5HG4/s1600/PK5_9447-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhc5sCdHn0syM1MSNcZYoJGxXjHW1qupQYlS6bNgh0aVi9F4a3dLZ1BNwODNxM17Mvh0Yum-0WtdFNTFe5DDh4AeefnWV5FwkgRIt-qovux6ycBJHCkmTerAeMVKonGQ_9IOKTIGeE5HG4/s320/PK5_9447-klein.jpg" width="231" /></a></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-83504096102503522172011-06-21T23:01:00.000+02:002011-06-21T23:01:17.206+02:0019-inch cabinetsNetwork equipment is often placed in cabinets that happen to be 19" wide. Now I first have to explain to my students that 19" is read as <i>19 inches</i>, where <i>inch</i> is the imperial unit of length used in South Africa until the end of the 1960s. (It is still used in a few places in the world.) The simplest rule of thumb to covert between imperial and metric units of length is to remember that a standard ruler was 12" (that is 1', or one foot) long and those same rulers are now 30cm long. Hence we are talking about cabinets that are 47.5cm wide, but nobody calls them 47.5cm cabinets. Some people do call them 19" racks, though. (A more precise conversion of 19" is 482.6mm.)<br />
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Below is a picture of such a 19" cabinet. The glass door has been opened so one can clearly see the innards. The most important things no notice are the 'pillars' with square holes in them on both sides of the cabinet.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_atjDIsEizmioKY1XaCf1nC8LnUIC-y6b-DB6FksBY6Jx-R-DxuJHeVvkx_VkV1HCJlt9pX2rAjw13mq_nI09iqFDfs9s1XF2nsz7Vzt6_XzU6AoePHTefx0YZUiOKqtuJx9Q_tGP_HQ/s1600/PK5_8930-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="228" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_atjDIsEizmioKY1XaCf1nC8LnUIC-y6b-DB6FksBY6Jx-R-DxuJHeVvkx_VkV1HCJlt9pX2rAjw13mq_nI09iqFDfs9s1XF2nsz7Vzt6_XzU6AoePHTefx0YZUiOKqtuJx9Q_tGP_HQ/s320/PK5_8930-klein.jpg" width="320" /></a></div><br />
An old ruler has been placed at the bottom of the cabinet; it dates from the 1960s and is therefore marked in inches. The crop below shows that the distance from hole to hole is about 18".<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzlZKTox3gjtq7-4cvIkQ3KbrUJxS5iw6nFaM0j7Dj_tMQNZncwFHAn2Nn0VlsiHUoAxtSLNjDUYEja6_eyqADUGH7-NZu92Agi3zhSsDf6cW-KL8g-FWIPOmtxlOtO5UTyqrytlYTobs/s1600/PK5_8930-crop.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzlZKTox3gjtq7-4cvIkQ3KbrUJxS5iw6nFaM0j7Dj_tMQNZncwFHAn2Nn0VlsiHUoAxtSLNjDUYEja6_eyqADUGH7-NZu92Agi3zhSsDf6cW-KL8g-FWIPOmtxlOtO5UTyqrytlYTobs/s320/PK5_8930-crop.jpg" width="320" /></a></div><br />
In a real network many units will be fastened to the cabinet. The picture below is an example that shows a typical installation. Careful observation reveals that each of the pieces of equipment in this cabinet is exactly three holes high - somewhat more precisely they are 44.5mm high. The height of a cabinet is measured in units, abbreviated as U. Counting the holes in the cabinet above (27 holes) reveals that it is a 9U cabinet. Since the top and bottom of the cabinet in the picture below are not visible, it is not possible to determine its size from the picture. At least eleven units are visible in the picture, with spaces between some of them. This cabinet is obviously much bigger than our earlier example. Note that some pieces of equipment may be larger than 1U - a rack-mountable computer may, for example, be 2U high.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBLLaTfR-JyHb7Src52q84LyRF65SLMnAEqd1uh9Lg8U5zOLL78vC0qRyVfLK9-xVKaRLLdXg-MGMpw2jvO4i1RrCCwpbtKK8UNQsuDsbIOSqWpWx_DbyAVMYqCivlwmc66BE25p2BpEg/s1600/PK5_8823-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBLLaTfR-JyHb7Src52q84LyRF65SLMnAEqd1uh9Lg8U5zOLL78vC0qRyVfLK9-xVKaRLLdXg-MGMpw2jvO4i1RrCCwpbtKK8UNQsuDsbIOSqWpWx_DbyAVMYqCivlwmc66BE25p2BpEg/s320/PK5_8823-klein.jpg" width="212" /></a></div><br />
Here is the earlier cabinet again, this time from the inside. The rounded shape is distortion caused by the lens used. This cabinet has some horizontal pieces of metal, which is unusual. The most important piece of metal in this picture is still the pillar on the right with its holes that face the glass door.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTgrncEuApLNAZfYRT2MErPJgvMjL2qHNlTn8hjrrf4bNmo5Ge-Zqiqn8x3PcgCo7cKZTZdOaWaYAJcwEtsfTc3XBre7aqjGhHXmPS9OTdCP78QRTaGjWFCwIcI2yBocQViHalaYTPbGk/s1600/PK5_8933-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTgrncEuApLNAZfYRT2MErPJgvMjL2qHNlTn8hjrrf4bNmo5Ge-Zqiqn8x3PcgCo7cKZTZdOaWaYAJcwEtsfTc3XBre7aqjGhHXmPS9OTdCP78QRTaGjWFCwIcI2yBocQViHalaYTPbGk/s320/PK5_8933-klein.jpg" width="320" /></a></div><br />
The traditional way of fastening equipment to the cabinet is by means of bolts and cage nuts. Note the two nuts in the picture below are indeed in their own little cages.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhV4TJWYDom_Cp0x6xay-sTk3B3G9iw6nGpAFgVHRRvqmpZUQ3U8hk5L65EFimkDIZowUPT-aHYFnGSgSF8E4ZmL0G7qMdr_dIOZ7DN56s6k2hNszU02Us7GcRtvdLVld_MXQy0ObJsGh0/s1600/PK5_9385-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="233" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhV4TJWYDom_Cp0x6xay-sTk3B3G9iw6nGpAFgVHRRvqmpZUQ3U8hk5L65EFimkDIZowUPT-aHYFnGSgSF8E4ZmL0G7qMdr_dIOZ7DN56s6k2hNszU02Us7GcRtvdLVld_MXQy0ObJsGh0/s320/PK5_9385-klein.jpg" width="320" /></a></div><br />
A closeup makes the nature of the cage even clearer.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqeueZ17pj0BM3LUkUhu65E95Sx7mr9DmcWai3UIhVywMq-n8nIlykYNWtTLcS696-c3V29hjuI5pmYkBg6ZC8xE3RMt7QLnkoUOuKtJFGQYhI49n3Ld64raaVmW6Co5yteB893FDro54/s1600/PK5_9407-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjqeueZ17pj0BM3LUkUhu65E95Sx7mr9DmcWai3UIhVywMq-n8nIlykYNWtTLcS696-c3V29hjuI5pmYkBg6ZC8xE3RMt7QLnkoUOuKtJFGQYhI49n3Ld64raaVmW6Co5yteB893FDro54/s320/PK5_9407-klein.jpg" width="320" /></a></div><br />
To use the cage nuts they are clipped into the square holes of the front pillars. The picture below shows how the caging clips into the hole and the cage then holds the nut in place. It is now possible to fasten a piece of equipment from the front without having to try to hold the nut at the back.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRYVQOwGg1DNfS-YzKRxFEwKBBNpsKj5J2Wi7EMuyURt3w2wmMGXUTjzzQWNvdwkbVmVU7ZyNClY-VOfR6MqgEtPNufl_RM-Uv5xAvkeRXOmpigsya1FmdRexavux8tHOf6I7fPH1cWDA/s1600/PK5_9391-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRYVQOwGg1DNfS-YzKRxFEwKBBNpsKj5J2Wi7EMuyURt3w2wmMGXUTjzzQWNvdwkbVmVU7ZyNClY-VOfR6MqgEtPNufl_RM-Uv5xAvkeRXOmpigsya1FmdRexavux8tHOf6I7fPH1cWDA/s320/PK5_9391-klein.jpg" width="127" /></a></div><br />
In the picture below two bolts have been screwed into nuts. In this case they hold a matchstick - to indicate scale. These two screws have one hole open between them. The matchstick is therefore about 1U high.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyHtziSt8_17hYQddaPsfsSkbOxL5TUGCq8MsaZ3t5nSjLLghznfX5jduhyJO1hWlUCCBObtOvA_SiEafJ_80uxzmHltD1MOTiv1V1BBZXL0_R8s91Tg920piTjsqBXLkiQxeUQ3_wfIg/s1600/PK5_9399-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyHtziSt8_17hYQddaPsfsSkbOxL5TUGCq8MsaZ3t5nSjLLghznfX5jduhyJO1hWlUCCBObtOvA_SiEafJ_80uxzmHltD1MOTiv1V1BBZXL0_R8s91Tg920piTjsqBXLkiQxeUQ3_wfIg/s320/PK5_9399-klein.jpg" width="214" /></a></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-89310923520091442662011-06-20T19:36:00.000+02:002011-06-20T19:36:22.897+02:00TrunkingIn many office buildings a wire conduit runs along some of the walls that enables one to easily install a new cable to any office (and, in principle, to remove old unused cables). The terms <i>reticulation</i> or <i>cable management</i> are used for guiding cable through such conduits. Often the conduits are installed about 1m above the floor to make it easy to plug plugs into sockets installed in the conduits. Such conduits are known as <i>trunking</i>. (Apparently they are known as <i>wireways</i> in some parts of the world.)<br />
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Here is an example of trunking installed just below the window sill in an office that will not be identified.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiirJ5ewMRVqOYOQtYZ_AyiDRGhQcTKCH2us7s7qwO_NtHUnZhAdqlwle5jEZ91MwhbKJuM2IWIal5jAeKgrPgpq5YrD95VrI4XhCGrlU50EADXbzNGr9Wi3j_jKFJ_PEXw0WoMIaIi77o/s1600/PK5_9372-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiirJ5ewMRVqOYOQtYZ_AyiDRGhQcTKCH2us7s7qwO_NtHUnZhAdqlwle5jEZ91MwhbKJuM2IWIal5jAeKgrPgpq5YrD95VrI4XhCGrlU50EADXbzNGr9Wi3j_jKFJ_PEXw0WoMIaIi77o/s320/PK5_9372-klein.jpg" width="198" /></a></div><br />
Viewed from a more conventional angle one can see a South African electrical socket on the cover over the top duct and several sockets and cables attached to the cover on the bottom duct.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLvH5KdDjpOWErTQ22K6OACdfFSbgBE2c5bH_cfOo_yye03I0dP2kAHc8Ij2kx21-befGzZLLtgYc-yADjXqm9SWd7yBpczocuLh6OEOG46E3GyUKGzXhV2ODhZjELz5lxpstyY0prkxI/s1600/PK5_9375-edited.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="119" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLvH5KdDjpOWErTQ22K6OACdfFSbgBE2c5bH_cfOo_yye03I0dP2kAHc8Ij2kx21-befGzZLLtgYc-yADjXqm9SWd7yBpczocuLh6OEOG46E3GyUKGzXhV2ODhZjELz5lxpstyY0prkxI/s320/PK5_9375-edited.jpg" width="320" /></a></div>The first socket on the bottom lid is an old South African telephone socket featured in an <a href="http://www.networkmuseum.net/2011/06/phone-plugs.html"><span id="goog_430030150"></span>earlier post<span id="goog_430030151"></span></a>. It is no longer being used in this installation. Next, just below the electrical socket, is a pair of thinnet coaxial cables. The logic of having a pair is that one goes to the left in the duct and the other to the right. The coax cables are no longer being used in this installation. The third item is a pair of RJ-45 sockets. They are actively being used. Finally there is a pushbutton that once upon a time could open the security door that allows access to the corridor. The button is no longer being used in this installation.<br />
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Removing the covers reveals the innards of the trunking.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGu3tl7QtVpfn-uK6Yu9fJO2Lf6x40Pkro0uSOj0xCbXRcnW_2IFfRy9DrUZyUBUaAitZQulIUyogeYaehtPE990ba7feZMWCvdUdEQ8KV4RzV289bySDTKi76Xf7D372ef3JsRrGIVZU/s1600/PK5_9369-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGu3tl7QtVpfn-uK6Yu9fJO2Lf6x40Pkro0uSOj0xCbXRcnW_2IFfRy9DrUZyUBUaAitZQulIUyogeYaehtPE990ba7feZMWCvdUdEQ8KV4RzV289bySDTKi76Xf7D372ef3JsRrGIVZU/s320/PK5_9369-klein.jpg" width="320" /></a></div>The top duct clearly carries the power lines - live, neutral and earth.<br />
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The middle duct is unused.<br />
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The bottom duct contains a large number of UTP cables - as one would expect in a modern setup. Note the black coaxial and cream phone cables also making an appearance. Also note the loops in some of the cables: When installing cables one quickly learns to take a cable beyond its intended termination point and then return with a loop. This gives one some space to work when attaching the socket or other fixture to the end of the cable.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-77881398290567861852011-06-12T15:47:00.001+02:002011-06-12T16:08:30.440+02:00Phone plugsMany South Africans will remember the phone plugs used in the old days - the plug shown in the picture below. In fact, many probably still use these old plugs. (I remember when these old plugs were the new ones that replaced an even older variety...)<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX7sPQ20CGRw69f-KB82Xoly7gT95zj_5F6lT805S6y-DWUIreWRnRLS8GpIPx2_7HjYQh8oXUZrDnXkWHKo9yu9f4alBWMN-lLGrt_CcRgaF6aLcmhBOCXDXStSLkD8dsV0r2pDlDnQs/s1600/PK5_8914-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX7sPQ20CGRw69f-KB82Xoly7gT95zj_5F6lT805S6y-DWUIreWRnRLS8GpIPx2_7HjYQh8oXUZrDnXkWHKo9yu9f4alBWMN-lLGrt_CcRgaF6aLcmhBOCXDXStSLkD8dsV0r2pDlDnQs/s320/PK5_8914-klein.jpg" width="320" /></a></div>Of course, early modems sold in South Africa used the exact same plug. However, in later years modems had the now ubiquitous RJ-11 plugs and came with a separate adapter.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2ffjCpRRjzwLdn7O6DdK0_NBMflcOwYZB_lebeZVg955jpqNovKKUEFIhithaehnkBEDGCjFW7sdlqkk8b0iXZpv8uiMXU2oizqpv0bTnxJxvuv9nb0ddDmFphyl62ft3FVYS75L2sxs/s1600/PK5_8916-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2ffjCpRRjzwLdn7O6DdK0_NBMflcOwYZB_lebeZVg955jpqNovKKUEFIhithaehnkBEDGCjFW7sdlqkk8b0iXZpv8uiMXU2oizqpv0bTnxJxvuv9nb0ddDmFphyl62ft3FVYS75L2sxs/s320/PK5_8916-klein.jpg" width="320" /></a></div>The RJ-11 socket should look familiar to most readers of this post.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_msb70iu6QGsOn5nPXusjkyv389IAYc-2HzcVm8pVTgyOiRCShp3YZBl_uC8LKCEOI_TFmFiCFuEz37fWC7FTgAcgCAQnODU_tIjx0Z9s0_KslmeglMvrYgUCQzIraxpA2KJEEW3KMrA/s1600/PK5_8918-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi_msb70iu6QGsOn5nPXusjkyv389IAYc-2HzcVm8pVTgyOiRCShp3YZBl_uC8LKCEOI_TFmFiCFuEz37fWC7FTgAcgCAQnODU_tIjx0Z9s0_KslmeglMvrYgUCQzIraxpA2KJEEW3KMrA/s320/PK5_8918-klein.jpg" width="320" /></a></div>It's the other end that looks strange to a new generation of students.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiycLFwbkgxrdDELlkDurDm2aeCv94eLjFedQC_FDYjBitUSXgkBRLC3nw8ly4P2aFeuynDi0XOUMPpMadhyXJFUQ1wEtcPRP9B0KGdzOWOEiz5wuKCEehKJWpatIx5cAfnCpKr_i6U-fw/s1600/PK5_8919-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiycLFwbkgxrdDELlkDurDm2aeCv94eLjFedQC_FDYjBitUSXgkBRLC3nw8ly4P2aFeuynDi0XOUMPpMadhyXJFUQ1wEtcPRP9B0KGdzOWOEiz5wuKCEehKJWpatIx5cAfnCpKr_i6U-fw/s320/PK5_8919-klein.jpg" width="320" /></a></div>Of course, it's not only South Africa who had strange phone plugs. Many kits were available that allowed one to convert local phone sockets to RJ-11 sockets wherever one travelled in the world. The picture below shows one such kit manufactured by Targus that enabled one to travel through most of Europe and remain connected.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdHW-fjWO-zLmROeHB5AFQip76O9izaEh4VGjeokfNC9Q4W-0FPxc14xkIkTsU_YxI0GIUgMRx5XZjYIegQFTDI9Iq2M1i89dotrNw4VlaiNj2U6Q_2cJpCG8YiR1weNjZNCojCdCxA9g/s1600/pk5_8921-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdHW-fjWO-zLmROeHB5AFQip76O9izaEh4VGjeokfNC9Q4W-0FPxc14xkIkTsU_YxI0GIUgMRx5XZjYIegQFTDI9Iq2M1i89dotrNw4VlaiNj2U6Q_2cJpCG8YiR1weNjZNCojCdCxA9g/s320/pk5_8921-klein.jpg" width="258" /></a></div>All these plugs split the local socket into an RJ-11 socket, as well as a local socket. One could therefore unplug the phone in one's hotel room, plug in the adapter, and then plug the phone back into the adapter. In addition one could plug one's modem into the RJ-11 socket of the adapter.<br />
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Here are the 'business ends' of the adapters.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQlUdwIeVbdk5qmSlnq8JkUwkmT8vIikG8e2g31tjBizHgRWIny_sC8ZJIzvEpS84s5ZZZbkC_z23XucW5GFslLd0ugsCFl-TCPLDZ052B0AFmjJAy_YuCkjj6BqBN1HqQORilkctcO8I/s1600/PK5_8923-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQlUdwIeVbdk5qmSlnq8JkUwkmT8vIikG8e2g31tjBizHgRWIny_sC8ZJIzvEpS84s5ZZZbkC_z23XucW5GFslLd0ugsCFl-TCPLDZ052B0AFmjJAy_YuCkjj6BqBN1HqQORilkctcO8I/s320/PK5_8923-klein.jpg" width="246" /></a></div>Unfortunately these plugs did not solve all one's problems. One also needed a local ISP to call. Alternatively one had to make an incredibly expensive call to one's home country that typically suffered from really bad interference. The best option was to use an ISP with an international presence.or one that had a roaming agreement with various national ISPs. Unfortunately such ISPs were scarce - especially in the early years of mobile computing.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-24583195065866658822011-06-11T21:11:00.000+02:002011-06-11T21:11:01.664+02:00ThicknetOriginally LANs were built using a rather thick variety of coaxial cable. Later, when a thinner version was adopted, the original was colloquially referred to as <i>thicknet</i> and the later variety as <i>thinnet</i>.<br />
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A cross-section through thicknet looks more or less as one would expect.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijwvs4F_2o6G5opx_yRj912hjbakimLlb5GHczc22U_46_PSVFe9g_2pbuSuHJa5M6nOOFqcTZ5zj6uKROemh_xYb9d4NaFRHVbOgrYT6iy1d79W4xuPtgBDUOLdt2LsbCtMZyG8xQMW4/s1600/PK5_8903-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijwvs4F_2o6G5opx_yRj912hjbakimLlb5GHczc22U_46_PSVFe9g_2pbuSuHJa5M6nOOFqcTZ5zj6uKROemh_xYb9d4NaFRHVbOgrYT6iy1d79W4xuPtgBDUOLdt2LsbCtMZyG8xQMW4/s320/PK5_8903-klein.jpg" width="320" /></a></div><br />
Nobody can deny the inherent beauty in such cables.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-lnhlGvV8NOrCGksKCRmQGuJR_WHfVooWe8iXxlRZJpXPKhH4yBQs_g7FAOk6UcLQtTmm3nNkUvaDmk7T1KwRQYyk3bYw1Uke8rwysKmRRM1geyHjfGLEKQgMey2GXN_VsFSbvuz2KKU/s1600/PK5_8904-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="271" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg-lnhlGvV8NOrCGksKCRmQGuJR_WHfVooWe8iXxlRZJpXPKhH4yBQs_g7FAOk6UcLQtTmm3nNkUvaDmk7T1KwRQYyk3bYw1Uke8rwysKmRRM1geyHjfGLEKQgMey2GXN_VsFSbvuz2KKU/s320/PK5_8904-klein.jpg" width="320" /></a></div><br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLHAyuZx-7G7Z2IvVw4wl93PmfBI30Qkko7oVslv3_RgcKjM4kLPhjiT_y3v3TjhigHsyO8cDESYh2IzQD1q8E8unS9zjeFwXl7zUgJQDDVRBwB5zBg7tZx2rtWOq6tUyGB5o6xGc33tQ/s1600/PK5_8906-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="124" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLHAyuZx-7G7Z2IvVw4wl93PmfBI30Qkko7oVslv3_RgcKjM4kLPhjiT_y3v3TjhigHsyO8cDESYh2IzQD1q8E8unS9zjeFwXl7zUgJQDDVRBwB5zBg7tZx2rtWOq6tUyGB5o6xGc33tQ/s320/PK5_8906-klein.jpg" width="320" /></a></div><br />
As always a sense of scale might be useful.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_1juORgCj27oOIv-ODlFZg7JbTVbLNY8GEQBfc7fQX6u8Qc07pKF9HxMynVVD4Uc43HuK0tspg1b8Nn40Zd5NS3A6eINLXow_nWRgsRCNP3_JtYl5tLReBldXnhGe6sKfyxTM41JabQc/s1600/PK5_8908-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="312" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_1juORgCj27oOIv-ODlFZg7JbTVbLNY8GEQBfc7fQX6u8Qc07pKF9HxMynVVD4Uc43HuK0tspg1b8Nn40Zd5NS3A6eINLXow_nWRgsRCNP3_JtYl5tLReBldXnhGe6sKfyxTM41JabQc/s320/PK5_8908-klein.jpg" width="320" /></a></div><br />
A more realistic comparison is one with related cables.<br />
<div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBdOsTJQnXcsj60qkmO5fsCoyyOXNFU7o6XuBKnsfXaTbd4p3nEoeNCh4vQngTJz8wvPhP9vXpU8e4WwYp1JVBMbD7y8ncJ6xHG8JJEJjAm5EssLi5GyRpymBwWfncmwOi__JktYa-GmE/s1600/PK5_8884-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="221" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBdOsTJQnXcsj60qkmO5fsCoyyOXNFU7o6XuBKnsfXaTbd4p3nEoeNCh4vQngTJz8wvPhP9vXpU8e4WwYp1JVBMbD7y8ncJ6xHG8JJEJjAm5EssLi5GyRpymBwWfncmwOi__JktYa-GmE/s320/PK5_8884-klein.jpg" width="320" /></a></div>The coax on the left is thicknet. Officially it is known as RG-8/U or, in Ethernet applications, as 10Base5. The 10Base5 designation stems from the fact that it could be used for baseband transmissions at 10Mbps over distances of up to 500m.<br />
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Next to the thicknet is an example that looks like thinnet. This example is RG-59B/U. Real thinnet looks very similar, but has an impedance of 50Ω, compared to the 75Ω of RG59B/U.<br />
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The white coax is RG-6/U - commonly used to connect antennas and satellite dishes to TV sets.<br />
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The final cable is Cat 5e UTP - commonly used in current network installations.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-49830250424194357472011-06-10T19:33:00.000+02:002011-06-10T19:33:20.549+02:00Air-blown fibre - Part 3Air-blown fibre, <a href="http://www.networkmuseum.net/2011/06/air-blown-fibre.html">as noted earlier</a>, is blown through a microtube that is installed between the two endpoints. Such microtubes may be connected using various connectors. A simple example is one that provides a straight-through connection. Here is an example.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjopAh9I4T9b5alTBMRwFmEbRKWt-y9mnxpwyPJUoZH03ToUD64aNFdqu6iwogspxILJCqCJam4zFStgrhGD2bi9M_8UhCeA7xDb3D7Vkm-m9r2wDh5l6D3BHhGqlURksDSYre-6ijltZI/s1600/PK5_8882-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="160" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjopAh9I4T9b5alTBMRwFmEbRKWt-y9mnxpwyPJUoZH03ToUD64aNFdqu6iwogspxILJCqCJam4zFStgrhGD2bi9M_8UhCeA7xDb3D7Vkm-m9r2wDh5l6D3BHhGqlURksDSYre-6ijltZI/s320/PK5_8882-klein.jpg" width="320" /></a></div>To connect a tube it is simply pushed into the connector, which locks it in place. The tube it should be connected to is inserted at the opposite side.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsVaqALrb084q98aMyyrU69vMxCJBB6UCExsTP9HRGyImsLH8lZcK_qSybuKyEwKj9GqDkitfCleaw4WOwuRsvqXAOOnN0MwGOHgaT2Zipc5lxpvZhkDgtHt8b6UqI1Up-9JOzyLwWZcc/s1600/PK5_8881-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="158" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsVaqALrb084q98aMyyrU69vMxCJBB6UCExsTP9HRGyImsLH8lZcK_qSybuKyEwKj9GqDkitfCleaw4WOwuRsvqXAOOnN0MwGOHgaT2Zipc5lxpvZhkDgtHt8b6UqI1Up-9JOzyLwWZcc/s320/PK5_8881-klein.jpg" width="320" /></a></div>To release the tube again, the white ring at the edge of the connector is pushed inwards.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-39053142683626214422011-06-09T00:11:00.001+02:002011-07-04T10:04:53.889+02:00Air-blown fibre - Part 2The air-blown fibre shown <a href="http://www.networkmuseum.net/2011/06/air-blown-fibre.html">below</a> has yet more secrets to reveal.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvXkbd17jsxhlsutdzWNMVLzizrtk9hSbwBNfCj2Uq4qsmw7Yw4w2CR4wz7mjXENgcrGcqc3n_ef-K1CJCJlOf1WKypG4V2BpulOPUIu0hE3aAw_64-USF2-2LghMa7GOPEN8WGj-YdWQ/s1600/PK5_8864-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvXkbd17jsxhlsutdzWNMVLzizrtk9hSbwBNfCj2Uq4qsmw7Yw4w2CR4wz7mjXENgcrGcqc3n_ef-K1CJCJlOf1WKypG4V2BpulOPUIu0hE3aAw_64-USF2-2LghMa7GOPEN8WGj-YdWQ/s320/PK5_8864-klein.jpg" width="320" /></a></div>Now one can clearly see the eight cores (or eight fibres) in the single 'fibre'<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKzxaTQe0NUuqmKKw9-5J70KvlOA0L7lVMq3Ir9f6-jjJsFoX96ZkdXR19xj5xcSSr8jeuLurejKr_kL7uwjUoB_KZCbWjbmI6PXAU0AfH4E2RD-cVnJOxtQiItLzneLZmCuQwAB1qJwc/s1600/PK5_8864b-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKzxaTQe0NUuqmKKw9-5J70KvlOA0L7lVMq3Ir9f6-jjJsFoX96ZkdXR19xj5xcSSr8jeuLurejKr_kL7uwjUoB_KZCbWjbmI6PXAU0AfH4E2RD-cVnJOxtQiItLzneLZmCuQwAB1qJwc/s320/PK5_8864b-klein.jpg" width="320" /></a></div>Zoomed in a bit more matters become even more obvious.<br />
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Yet again we need our matchstick to get a sense of scale.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgcKkHO0tswzWD3GX9pUxwOpCYiG_WDh3yqHFkdBfsBrOo_DbvQhN-IyF6RC80JWOqyfcsT4BVNII_PlQPLqPTASFCPv9VUvBsKq9TCJDUY5yLfCfe11Q6ZprrikGZj-chIv5hvumZ_-gg/s1600/pk5_8865-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgcKkHO0tswzWD3GX9pUxwOpCYiG_WDh3yqHFkdBfsBrOo_DbvQhN-IyF6RC80JWOqyfcsT4BVNII_PlQPLqPTASFCPv9VUvBsKq9TCJDUY5yLfCfe11Q6ZprrikGZj-chIv5hvumZ_-gg/s320/pk5_8865-klein.jpg" width="309" /></a></div><br />
Perhaps the setup to take these pictures may be interesting to some readers.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifjrkO-pWgKmaxRM_r_XxIfIQzAzQ4jESiCxYStc3bmfTjFHTCIHrNyr0SuPVBL3xDPyD9SH9ZRar9OKgbEjI1xFqsyX5UwSIMn1NovHd6UtByelt45RWDSo54i6Ume07rUbIecris2-0/s1600/P1000025-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifjrkO-pWgKmaxRM_r_XxIfIQzAzQ4jESiCxYStc3bmfTjFHTCIHrNyr0SuPVBL3xDPyD9SH9ZRar9OKgbEjI1xFqsyX5UwSIMn1NovHd6UtByelt45RWDSo54i6Ume07rUbIecris2-0/s320/P1000025-klein.jpg" width="237" /></a></div>In this case a Pentax K-5 (silver!) fitted with a Pentax Auto Bellows K and a Pentax DFA 100 f/2.8 manually stopped down to f/8 at an exposure time of about 15s was used. Strange how the auto functions of years gone by become manual (if they are old enough). The Auto Bellows can step down the lens, but no longer fire the shutter, because the shutter mechanism is triggered by an electrical contact. I cannot use my latest DA lenses because they have no aperture ring to limit the degree of stopping down that will occur. But I am digressing. The next post will focus on networks again.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-88026095825817949392011-06-07T22:20:00.002+02:002011-06-08T11:29:51.044+02:00Air-blown fibreInstalling optical fibre can be a costly and difficult process. One relatively recent option to ease the task is known as air-blown fibre. Rather than installing expensive fibre, one installs tubes, which look like straws that are often bundled together.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLO7elXUGudWtkF8wyKjVy1JrnZDgRB7VLEZsQFKtrcbdRJm88af04s8wdkz7p0fkxzUsw9IniOq7UnPM0vQlzdKcAVJmzKZdZjWhV-jigaUApNxbLhVaAkUcdpYDXFD43kGQ9BrdD82w/s1600/pk5_8836-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="229" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjLO7elXUGudWtkF8wyKjVy1JrnZDgRB7VLEZsQFKtrcbdRJm88af04s8wdkz7p0fkxzUsw9IniOq7UnPM0vQlzdKcAVJmzKZdZjWhV-jigaUApNxbLhVaAkUcdpYDXFD43kGQ9BrdD82w/s320/pk5_8836-klein.jpg" width="320" /></a></div><br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigZUuJvSS3bnbf_-UllQGLyskUqTulq3TwnJ1djufXawDk3eSYbcV1-lDyzW_tNroy1szLa251Jdxwl-1La5OsrMkC3XOGXdDuJ8mSs13Js9IXZLmguauIjOlulPjKh2-yYfy9hKJKeWI/s1600/PK5_8838-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="127" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigZUuJvSS3bnbf_-UllQGLyskUqTulq3TwnJ1djufXawDk3eSYbcV1-lDyzW_tNroy1szLa251Jdxwl-1La5OsrMkC3XOGXdDuJ8mSs13Js9IXZLmguauIjOlulPjKh2-yYfy9hKJKeWI/s320/PK5_8838-klein.jpg" width="320" /></a></div>Fibre is then blown through these tubes as required. The tubes may be installed over hundreds of meters - even a few kilometers. And fibre can be blown through the tubes at tens to hundreds of meters per second. Initially more tubes can be installed than required and fibre could be blown through them when required. And an obsolete fibre can be removed and replaced with a new one.<br />
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The next picture shows a fibre in one of the tubes.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWX0Gk1dkDWQXKxshCdFlc7L3rLm4yv1_2jlYIXORlApesjCvc5eMUkuUS7uMqjIVy60E1IykKWSVZGsWrP2dq_8bYy889u37dknNWFyMz5mkTrkiYWESTunm9fMn12uqRHzPVPWOiNTE/s1600/PK5_8844-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="238" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWX0Gk1dkDWQXKxshCdFlc7L3rLm4yv1_2jlYIXORlApesjCvc5eMUkuUS7uMqjIVy60E1IykKWSVZGsWrP2dq_8bYy889u37dknNWFyMz5mkTrkiYWESTunm9fMn12uqRHzPVPWOiNTE/s320/PK5_8844-klein.jpg" width="320" /></a></div>When one shines a light through the fibre it becomes clear that it actually consists of several fibres (or cores). The next picture contains the same fibre as above, but this time lighted from the other end.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJo6sa4X30p-tF_wjPg8872JURfjKziM1RJOXuDrV_BGtHVw4P2IcxpQ2HhbpkjStv5DnKw2tz4k_ayInG2QpexLNZJ4RVIYTTOjxeALAUP6uNFyKIK9mccw5DNp0qhTzqa7M9yr2Itz4/s1600/PK5_8854-edited.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="194" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJo6sa4X30p-tF_wjPg8872JURfjKziM1RJOXuDrV_BGtHVw4P2IcxpQ2HhbpkjStv5DnKw2tz4k_ayInG2QpexLNZJ4RVIYTTOjxeALAUP6uNFyKIK9mccw5DNp0qhTzqa7M9yr2Itz4/s320/PK5_8854-edited.jpg" width="320" /></a></div>Of course we need an image with a matchstick in it for a sense of scale. The following picture not only includes the matchstick, but also shows the fibre above with its outer coating stripped away.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQLy8D6SgFkZKn2x6mTNlHX2NryjhUmdAPAP-28c6869RY_sZZAuRzt61-MaqtXLJguL5i-nkktL3G6WRh4z8X8b5LhedhBV6bAE1Ryw2XsCvUxGJNaFOCWSXDzv5ff3FODi5rQAu7UZY/s1600/P1000023-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="160" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQLy8D6SgFkZKn2x6mTNlHX2NryjhUmdAPAP-28c6869RY_sZZAuRzt61-MaqtXLJguL5i-nkktL3G6WRh4z8X8b5LhedhBV6bAE1Ryw2XsCvUxGJNaFOCWSXDzv5ff3FODi5rQAu7UZY/s320/P1000023-klein.jpg" width="320" /></a></div><br />
To take matters to the real world, the next picture was taken at the place in a network room where all the various parts of some big network come together. Various pieces of optical fibre are visible. In particular, note the microtubes (making loops!) through which fibre has been blown to other buildings.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAyWXFL5rdXWr8cyYyVm3TTlvvK5ofAEjVHObABGRN_TTwShq6P5xFjDUo-Kx8p_81oAxiorD5epbZi_-4v99vMNMPuUlZzNXZqwWbvkh6u5oU8-Z0opRBtNOsRioVgwWSytelKJq6QYk/s1600/PK5_8827-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAyWXFL5rdXWr8cyYyVm3TTlvvK5ofAEjVHObABGRN_TTwShq6P5xFjDUo-Kx8p_81oAxiorD5epbZi_-4v99vMNMPuUlZzNXZqwWbvkh6u5oU8-Z0opRBtNOsRioVgwWSytelKJq6QYk/s320/PK5_8827-klein.jpg" width="212" /></a></div>Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-70743031044736463752011-06-03T20:50:00.002+02:002011-06-04T08:53:25.477+02:00Building the netbook - circa 1998A small, highly portable laptop that can be used for typing and sending emails seemed necessary to me for as long as I can remember. Whether such a machine was fast or had a big screen did not matter. In other words, I have been craving the netbook long before its inception. However, even though it feels like an eternity, the option to build such machines is a relatively recent one. The laptop with the monochrome screen mentioned in <a href="http://www.networkmuseum.net/2011/05/rau-on-netscape-navigator-301.html">an earlier post</a> was my first such machine. I now found the receipt: 1997! It is less than 15 years old, has 20MB of memory and a 400MB disc...<br />
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One thing missing from many (most?) laptops of the time was any real mechanism to network it. Dial-up was one option using some external modem. A later post will talk about this. But to have a truly networkable laptop, one needed a real network interface. So I got a 3Com Etherlink III 3C589C LAN PC card for my 1997 laptop.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoRGIOpl_r3VCys0MGmaC-LLddw2iHS6b6DyejymDTXrQ1_OjDxooRK-Z8chcfnm-6kjxsEcIc6edKRZEANcoc3D9TanJiUyUs_gIndl1y1hS_jj5JwB8gesqiW6XISWH8k4SfAVULkdU/s1600/PK5_8768-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="147" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoRGIOpl_r3VCys0MGmaC-LLddw2iHS6b6DyejymDTXrQ1_OjDxooRK-Z8chcfnm-6kjxsEcIc6edKRZEANcoc3D9TanJiUyUs_gIndl1y1hS_jj5JwB8gesqiW6XISWH8k4SfAVULkdU/s320/PK5_8768-klein.jpg" width="320" /></a></div>As can be see from the photo, the interface consisted of two parts: a dongle and a PCMCIA card (or, as some people insisted to call it: a PC card, which was technically correct).<br />
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The dongle is obviously the part that connected to the network. Most networks I wanted to connect to used coax, but it was obvious that UTP was coming. So, I tried to future-proof my investment by buying a dual adapter - one that could connect to coax using a BNC connector, as well as to UTP, using an RJ-45 plug. Alas, the UTP connection was only a 10BaseT, and 10Mbps soon turned out to be too slow.<br />
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Here one sees the card and dongle assembled - ready to be inserted into the laptop's PCMCIA slot.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWvTE50mYkAje7OwGwP5l0gBFElDHfQKQlDw6LoKn6IZmauShUfoQrcV_00wB67ThtMyakbCgGoOyOkJFWUTgvkmVjyst5AawJuK3Bkj5ck9qzC4bXMAJN-ZR7UvXJUK9t8HZMzU6AJOg/s1600/PK5_8771-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="236" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWvTE50mYkAje7OwGwP5l0gBFElDHfQKQlDw6LoKn6IZmauShUfoQrcV_00wB67ThtMyakbCgGoOyOkJFWUTgvkmVjyst5AawJuK3Bkj5ck9qzC4bXMAJN-ZR7UvXJUK9t8HZMzU6AJOg/s320/PK5_8771-klein.jpg" width="320" /></a></div>But the need for speed had to be satisfied. And satisfaction came in the form of the SMC8040TX PCMCIA 10/100Mbps Fixed-Port Adapter.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5cz9boItT2XxO8SeWlTlSkzNp_QEBefYFFKGtRuX2t3X4lCeRt2KiSalNPT4lPf3VnLtik022IgWKdHE7xY6AdgvpHk5vM9GSHzr6V-fOW8fFU_X1ICqPF-3NLDeu-kUZYFd_l47E5e4/s1600/PK5_8772-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="173" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5cz9boItT2XxO8SeWlTlSkzNp_QEBefYFFKGtRuX2t3X4lCeRt2KiSalNPT4lPf3VnLtik022IgWKdHE7xY6AdgvpHk5vM9GSHzr6V-fOW8fFU_X1ICqPF-3NLDeu-kUZYFd_l47E5e4/s320/PK5_8772-klein.jpg" width="320" /></a></div>The SMC still could work at 10Mbps. But at 100Mbps it was ten times as fast as its predecessor.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjp-qPEuQmxxgwmKBJtxU54CSahlYZG-lVYX91IqFHdtX-Oy4QGOkfuB85Ph3fR8UHnY7DcTj-Oy3F-xrhPCs-qluC3eILxmnXrzNzSY6hSRDfIP6yhT3zlpwbjY3qSSJNA9n5x6ETrCm8/s1600/PK5_8773-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="212" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjp-qPEuQmxxgwmKBJtxU54CSahlYZG-lVYX91IqFHdtX-Oy4QGOkfuB85Ph3fR8UHnY7DcTj-Oy3F-xrhPCs-qluC3eILxmnXrzNzSY6hSRDfIP6yhT3zlpwbjY3qSSJNA9n5x6ETrCm8/s320/PK5_8773-klein.jpg" width="320" /></a></div>Obviously the SMC dates from the year 2000. For those who have not 'lived' the years 2000 to about 2004: Apple's iMac G3 was produced from 1998 onwards in a range of bright translucent colours. Following Apple's lead, everything else in those years was also produced in bright translucent colours. Here is our kettle circa 2000.<br />
<div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAEfJUO1ztvRRWQFn3lrRloEppkdEpoKL2n4xrYQKmP2bkc7MbEYXLpc7m7_4PiOh9k54DUUBGLySw2jTzcFyD9zllLSfx4KmS6oK_6HC_mdCX7u8MLIaRuGCyrauheClKCOe-wwfywfo/s1600/PK5_8784-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhAEfJUO1ztvRRWQFn3lrRloEppkdEpoKL2n4xrYQKmP2bkc7MbEYXLpc7m7_4PiOh9k54DUUBGLySw2jTzcFyD9zllLSfx4KmS6oK_6HC_mdCX7u8MLIaRuGCyrauheClKCOe-wwfywfo/s320/PK5_8784-klein.jpg" width="239" /></a></div><br />
There can't be too many fields where one can reminisce about the good old days a mere decade ago...Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-64995593375019416392011-06-03T10:45:00.001+02:002011-06-03T11:16:57.924+02:00Satellite phonesBelow is a rather poor picture of a satellite phone (and another in its box). I recently took the picture in a shop display in Johannesburg in rather poor light using my cell phone - hence the poor quality. The visible phone is intended for use with the Iridium constellation of low earth orbiting (LEO) satellites. Since the entire earth is covered by the constellation it is really true that one can make calls "from anywhere [on earth] to everywhere" on earth - unless one is somewhere where there is too much of an obstruction between the phone and the sky.<br />
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While the picture is poor it does illustrate the relative size of the phone's antenna when compared to the phone. The phone itself is rather bulky too.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTf1qrwmZZj1Y2_aVYRK_vqTVJp91UXu8LQwf3PpTj9NrnxRSzmDyN_3u9ByUcITvNwo4uMIR8220PrKoV5D1HG9rljkm665Hc31-Jn1Ol37KpfjepblRCVSC06nx4gIvZWqYpilNyfkM/s1600/NokN8219-edited.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="164" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTf1qrwmZZj1Y2_aVYRK_vqTVJp91UXu8LQwf3PpTj9NrnxRSzmDyN_3u9ByUcITvNwo4uMIR8220PrKoV5D1HG9rljkm665Hc31-Jn1Ol37KpfjepblRCVSC06nx4gIvZWqYpilNyfkM/s320/NokN8219-edited.jpg" width="320" /></a></div>I did wonder whether it was an option to buy one of these phones to have a physical example in my museum.. The answer is a resounding no. This cost of the phone is about R15 000. Calls currently typically cost between $1 and $2 (US) per minute (depending on where on earth you are). Data calls currently cost about $1.50 (US) per kilobyte. The phone weighs 266g. Its dimensions are 143x55x30mm. The battery lasts about 30 hours while on standby and about four hours when in use.<br />
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The phone (or, at least box) on the left uses the Inmarsat geostationary satellites (GEO). It is slightly heavier than the Iridium phone (279g vs 266g) and slightly bulkier (at 170x54x39mm). Interestingly, despite the higher altitude of the Inmarsat satellites, talk time is double that of the Iridium phone and claimed standby time is 100 hours. The claimed data rate is up to 20kbps.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-53803451046977150422011-05-31T22:39:00.000+02:002011-05-31T22:39:17.841+02:00African Undersea Cables<a href="http://manypossibilities.net/">Steve Song's</a> map of African undersea cables strikingly illustrates the changing landscape of African network connectivity. To get the most recent version of his map it is best to obtain it from <a href="http://manypossibilities.net/african-undersea-cables/">his site</a>. Here is the version of May 2011 reproduced with his kind permission.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizw3wD2dxTsF1lr4orH1SVo3QqGyVtuQzyaOO8pHEcTem7zH9Dg02PRkGaMFIafvU9dbmCAuL_tJGb9Rks58_CQkm3h2lcqj5bYqYl859pznGiIsZ5he3jELLc3QlEekpWDAGmr76f7HI/s1600/cable_map29.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="294" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizw3wD2dxTsF1lr4orH1SVo3QqGyVtuQzyaOO8pHEcTem7zH9Dg02PRkGaMFIafvU9dbmCAuL_tJGb9Rks58_CQkm3h2lcqj5bYqYl859pznGiIsZ5he3jELLc3QlEekpWDAGmr76f7HI/s320/cable_map29.png" width="320" /></a></div>It is almost unimaginable that, until recently, South Africa's only real undersea connectivity to the outside world was via the SAT3/SAFE cable system - a system which is hard to spot on this map.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-1539708333344109452011-05-31T19:28:00.003+02:002011-08-13T15:15:49.656+02:00RAU on Netscape Navigator 3.01I have just booted up one of my old laptops. One of the prominent applications on the (rather short) list of Windows 95 applications was Netscape Navigator 3.01. Upon opening it I found the following page still cached in it (dated 10 April 1997):<br />
<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJZQooTDG8ubgzjGNK2H3t0k_mhVtYA3qFqvw17XFq9_4803TO5ataVIrn-VdXVshzxMn_KjWKBv7IUIwXblPmQUAHzIZ_iwnyhQKmfEE-U0HP0rJieQUUOutEevSXeQD1UEtcssbUTAc/s1600/PK5_8762-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="242" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJZQooTDG8ubgzjGNK2H3t0k_mhVtYA3qFqvw17XFq9_4803TO5ataVIrn-VdXVshzxMn_KjWKBv7IUIwXblPmQUAHzIZ_iwnyhQKmfEE-U0HP0rJieQUUOutEevSXeQD1UEtcssbUTAc/s320/PK5_8762-klein.jpg" width="320" /></a></div>It should be noted that this is not a monochrome image. The display of the laptop was (and still is) monochrome. The smudges on the picture are imperfections developing on the display rather than dirt.<br />
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This was an early home page of the Rand Afrikaans University (RAU). (RAU was merged with other academic institutions to form the University of Johannesburg in 2005.) The homepage was typical of early university homepages. Usually they were developed by some 'techie' without any corporate involvement.<br />
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Scrolling down one finds the following useful information:<br />
<div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPuNPGhXPj06v33ryij0-QYxd1ClXhCHNTpXlS7HjiJVFW6HJhJeqlC13QMVWzYhnHadY2XvxCkeYRRPvHzwSL05kEqLvEvkt33OGs4re-HBgkuLAZMXW2qrzz8vqtCzZ5c1f1wDp1W5A/s1600/PK5_8763-klein.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="239" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPuNPGhXPj06v33ryij0-QYxd1ClXhCHNTpXlS7HjiJVFW6HJhJeqlC13QMVWzYhnHadY2XvxCkeYRRPvHzwSL05kEqLvEvkt33OGs4re-HBgkuLAZMXW2qrzz8vqtCzZ5c1f1wDp1W5A/s320/PK5_8763-klein.jpg" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><br />
</div>The 'general information' section consists of six links. Just finding something else to link to was an achievement - hence the links to sites such as CNN.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.comtag:blogger.com,1999:blog-6665953796962293071.post-67140501339205737102011-05-31T17:52:00.003+02:002011-05-31T18:23:50.531+02:00Wired: 1919 - from Shorpy<a href="http://www.shorpy.com/">Shorpy</a> is a great source of images from the distant past. Quite a number of them deal with topics of interest to networking enthusiasts.<br />
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Here is one such example that dates from circa 1919 and takes a "behind the scenes look at communications tech some 80 years after the telegraph tapped out its first message."<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEis6iLvf5DVDhCs78VX5YZ-87wJo6j2WmCYjMh4bJinF7eVyaOSvQ8FS4Z793kb378_AkojsBmTkkUQtPYVGFLeq-dPp3KXRvG2q-maA5ZO1rynefQqnvjzEHQmFWOvdDIgTs9SzviQpNs/s1600/20545a.preview.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEis6iLvf5DVDhCs78VX5YZ-87wJo6j2WmCYjMh4bJinF7eVyaOSvQ8FS4Z793kb378_AkojsBmTkkUQtPYVGFLeq-dPp3KXRvG2q-maA5ZO1rynefQqnvjzEHQmFWOvdDIgTs9SzviQpNs/s320/20545a.preview.jpg" width="252" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Wired: 1919<br />
(Used with <a href="http://www.shorpy.com/digital-images">kind permission</a> of <a href="http://www.shorpy.com/">Shorpy</a>)</td></tr>
</tbody></table>To really appreciate the detail one should look at the large version of the picture available from the <a href="http://www.shorpy.com/node/7945">original Shorpy post</a>. The comments left by Shorpy readers are usually also worth reading to gain a deeper insight into the details depicted in the photo.Martin Olivierhttp://www.blogger.com/profile/06576219134546063445noreply@blogger.com