<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Aug 30, 2015, at 11:09, Vint Cerf <<a href="mailto:vint@google.com" class="">vint@google.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">I used to manage the TYMNET engineering team when I was SVP at MCI and the protocols were by no means slapdash. They were quite carefully thought out. The mechanism was statistical multiplexing of keystrokes into frames for hop by hop transfer. As the frame arrived at the next hop, it was disassembled and new frames created including other keystrokes from other forwarders that lay along the source-to-destination paths to the target. Sort of like buses or airplanes full of people that land at a hub airport, and reassemble onto new buses or planes for the next hop.</div></div></blockquote><div><br class=""></div>Okay, so they weren’t slapdash. Yes, this sounds very close to the stat mux protocols that Codex did. They insisted it wasn’t packet switching but I finally convinced them that the only difference was the granularity. I later used this as the argument for why people should be considering ATM over IP, rather IP over ATM. ;-) It was the same idea.<br class=""><blockquote type="cite" class=""><div dir="ltr" class=""><div class=""><br class=""></div><div class="">There was a "colored ball" protocol to determine whether the train of keystrokes had been fully delivered to the destination by tossing in a colored ball and waiting for it to return. </div></div></blockquote><div><br class=""></div>This is what I thought was slap dash. I remember reading an early article (probably around 76 when the first Telenet articles were ) on TYMNET in which they described how they built the network and ran into problems and found they needed to add the “colored ball” stuff, which was something they should have seen before they started. I am sure that by the time you saw it at MCI it had evolved quite a bit.<br class=""><blockquote type="cite" class=""><div dir="ltr" class=""><div class=""><br class=""></div><div class="">Joe Rinde was one of the authors of the TYMNET protocols - he seems to have moved to Arizona and gone into the real estate business (!). </div><div class=""><br class=""></div><div class="">I am copying him (if the email is still valid) for his observations.</div><div class=""><br class=""></div><div class="">Joe - I recall that X.25 was an exterior "skin" for the TYMNET colored ball protocols and that X.75 was indeed in use for inter-network exchanges via X.25. Can you confirm?</div></div></blockquote><div><br class=""></div>That would make sense since X.25 was a DTE-DCE protocol and not necessarily a DCE-DCE protocol.</div><div><br class=""></div><div>Take care,</div><div>John<br class=""><blockquote type="cite" class=""><div dir="ltr" class=""><div class=""><br class=""></div><div class="">vint</div><div class=""><br class=""></div></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Sun, Aug 30, 2015 at 7:06 AM, John Day <span dir="ltr" class=""><<a href="mailto:jeanjour@comcast.net" target="_blank" class="">jeanjour@comcast.net</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word" class="">Not off the top of my head, but there were articles in conferences at the time on Tymnet and how it worked internally. The protocols were (I believe) mostly homegrown. What I remember about Tymnet was that they were pretty slapdash. They never saw anything coming until they ran into it, so even something like flow control was a retrofitted kludge. At least that is the impression, I had at the time.<div class=""><br class=""></div><div class="">Take care,</div><div class="">John</div><div class=""><div class="h5"><div class=""><div class=""><div class=""><blockquote type="cite" class=""><div class="">On Aug 30, 2015, at 06:22, Jim Carpenter <<a href="mailto:jim@deitygraveyard.com" target="_blank" class="">jim@deitygraveyard.com</a>> wrote:</div><br class=""><div class=""><p dir="ltr" class="">Telenet used X.75 inside but I'm not sure what Tymnet used or when they used it. If anybody has any recommended bedtime reading for (technical) details of the internals of Telenet and Tymnet, especially TYM2, I'd be quite interested.</p><p dir="ltr" class="">Jim Carpenter</p>
<div style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex" class=""><div dir="ltr" class="">the US-based Telenet and Tymnet both offered X.25 service and implemented X.75 I believe.</div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Sat, Aug 8, 2015 at 11:04 AM, John Day <span dir="ltr" class=""><<a href="mailto:jeanjour@comcast.net" target="_blank" class="">jeanjour@comcast.net</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">X.75 was widely used within PTT packet-offerings. As you would imagine mostly outside North America.<br class="">
<div class=""><div class=""><br class="">
<br class="">
> On Aug 8, 2015, at 10:18, Miles Fidelman <<a href="mailto:mfidelman@meetinghouse.net" target="_blank" class="">mfidelman@meetinghouse.net</a>> wrote:<br class="">
><br class="">
> Which raises an obvious question: Did X.75 ever get much traction? In<br class="">
> my days at BBN (1985-1992), and for a few years earlier, when I was<br class="">
> selling time sharing services, and using TELENET, I can't really recall<br class="">
> ever encountering it in real use.<br class="">
><br class="">
> Miles<br class="">
><br class="">
> Vint Cerf wrote:<br class="">
>> Larry Roberts asked me what he should use for protocol in Telenet and<br class="">
>> I said TCP but he said he could not sell datagrams and went on to<br class="">
>> develop X.25's virtual circuits with French, Canadian and UK<br class="">
>> assistance at CCITT (now ITU-T). That was standardized in 1976 while<br class="">
>> TCP was evolving. I told him we would run TCP (eventually TCP/IP) over<br class="">
>> X.25 and by 1981 or so that is what we did in CSNET. 1822 was never a<br class="">
>> contender for a global standard. X.25 begot X.75 which was the CCITT<br class="">
>> response to the Internet's TCP/IP.<br class="">
>><br class="">
>> OSI was yet another effort to craft a non-TCP/IP Internet and that got<br class="">
>> started in 1978, using X.25 as the underlying virtual circuit basis.<br class="">
>> Eventually an OSI connectionless mode was developed CLNP but never<br class="">
>> gained much popularity.<br class="">
>><br class="">
>> The TCP/IP vs OSI battle lasted from 1978 to 1993. X.25 was around<br class="">
>> from 1976 to 2003 or so as I recall. I shut down the last MCI X.25<br class="">
>> offering about 2003 or so if memory serves.<br class="">
>><br class="">
>> On Sat, Aug 8, 2015 at 3:42 AM, Miles Fidelman<br class="">
>> <<a href="mailto:mfidelman@meetinghouse.net" target="_blank" class="">mfidelman@meetinghouse.net</a> <mailto:<a href="mailto:mfidelman@meetinghouse.net" target="_blank" class="">mfidelman@meetinghouse.net</a>>> wrote:<br class="">
>><br class="">
>><br class="">
>>> On 08/08/2015 08:12, Jack Haverty wrote:<br class="">
>>> ...<br class="">
>>>> But I don't think there's much written<br class="">
>>>> material about that battle between TCP/IP and X.25 in the<br class="">
>> ARPANET arena.<br class="">
>><br class="">
>> Jack,<br class="">
>><br class="">
>> Granted that the TCP/IP cutover happened 2 years before I got to<br class="">
>> BBN, so my exposure wasn't quite firsthand -<br class="">
>> but weren't the battles really between 1822 and X.25, and then<br class="">
>> TCP/IP vs. the ISO stack? After all, 1822 and X.25 were both<br class="">
>> single subnet protocols, with no support for internetworking (and<br class="">
>> that IP runs over both of them, just fine).<br class="">
>><br class="">
>> Miles<br class="">
>><br class="">
>><br class="">
>><br class="">
>> --<br class="">
>> In theory, there is no difference between theory and practice.<br class="">
>> In practice, there is. .... Yogi Berra<br class="">
>><br class="">
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