[ih] Internet-history Digest, Vol 50, Issue 6

[Greg Skinner]

> On Jan 11, 2024, at 9:14 AM, Noel Chiappa via Internet-history <internet-history at elists.isoc.org> wrote:
> 
>> From:John Shoch
> 
>> When Xerox gave Alto/Ethernet/Dover/PUP systems to a number of
>> universities (Stanford, MIT, CMU, CalTech, Rochester), I think it included
>> Nova-based PUP "gateways"
> 
> Umm, no. I cannot speak with certainty about what Stanford and CMU got, but I
> can say with great certainty that all that MIT got was several UNIBUS
> Experimental Ethernet cards:
> 
>  https://gunkies.org/wiki/UNIBUS_Experimental_Ethernet_interface
> 
> I believe, from scraps I heard about what happened at Stanford and CMU, that
> it was the same there.
> 
> We had to write code to drive them; in the MIT AI Lab, the MIT-AI ITS machine's
> CHAOS-11 got a CHAOS->EFTP protocol translator (so they could print files on
> the Dover); in LCS, I added code the 'C Gateway' to both talk to the
> Experimental Ethernet (we sent IP packets over it; I assume that since PARC
> was on the fringes [yes, I know about the 'hints' early on] of the TCP/IP
> effort, they had already allocated an Experimental Ethernet packet type for
> IP, and we didn't have to ask for one), and speak PUP. (Although the only
> physical network on which it was prepared to send PUPs was our sole
> Experimental Ethernet - so why I wrote a PUP forwarder is a mystery to me -
> there was no place to send PUPs _to_.)
> 
> (The code for both survives - I was just looking at it to give authoritative
> answers about the CGW code. The CHAOS-11 code survives, too. If anyone is
> curious.)
> 
> Nobody at MIT made real use of PUPs; in LCS, we had IP, and in the AI Lab,
> they has CHAOS (and of course both had our own LANs, too). Dave Clark wrote a
> TCP for the Alto, and IIRC it was possible to TELNET from an Alto to a TCP/IP
> host. I suspect that most of the IP traffic on the Experimental Ethernet was
> TFTP packets headed to the Dover Spooler (which talked TFTP on one side, and
> EFTP on the other - although not via a protocol translator, I think; IIRC it
> 'buffered' files on disk).
> 
> 
>> which later led to the Stanford/Cisco multi-protocol routers)
> 
> From what I recall of Yeager's multi-protocol router at Stanford, that was
> true there, but I am not sure about MIT. (My memory is not clear on how much
> of an influence PUP was; see below for more - I now think it was not much.)
> At MIT, we had two competing protocol families entrenched (well entrenched,
> in the case of CHAOS; less so, for TCP/IP) before Ethernet and PUP arrived,
> and thus had a prior incentive to uncover the multi-protocol router approach.
> 
> There is a document from Dave Clark, "MIT Campus Network Implementation",
> iniial draft dated October 1982 (which I don't have in front of me, although
> I may have a copy buried in boxes somewhere), the one I do have is a later
> one, from June 1983. It captures an intermediate stage in the thinking of how
> multiple protocol families would be handled on the proposed MIT Campus Network.
> 
> It talks about two approaches, the first being an "MIT Standard Network
> Protocol", which would be a ubiquitous packet transport service. My
> recollection is that this was the only approach mentioned in the older draft
> - and that I didn't think it was practical. My take came from several
> previous attempts to do something like this for CHAOS and IP (the ill-fated
> 'MIT Protocol Word', or "Muppet"), which had utterly failed to get any
> traction. So I proposed the "multi-protocol spine" approach, and argued Dave
> into switching to that that approach in the later draft.
> 
> To answer charges that multi-protocol routers were impractical, I wrote
> multiple forwarders for the CGW (which was started, IIRC, to show that one
> could get acceptable performance from a packet switch written in a HLL; the
> prevous one I did was a mind-blowing kludge written in MACRO-11, whuch used
> intense macrology to instantiate all N^2 packet patha in a router with N
> interfaces - code also available). Which would explain why I wrote a PUP
> forwarder for it, when there was no earthly operational use for it. Dave's
> later draft refers to the CGW (not by name, though - merely a 'if you think
> this is not feasible, we have one working').
> 
> Dave's draft states that the protocol families the MIT Campus Network needed
> to support were CHAOS, DECNet, X.25, and IP. PUP is not mentioned (except in
> passing, as one of the protocols implemented on the 'see, it can be done'
> machine). This makes sense; as I mentioned, except for the CHAOS-11, no
> MIT machine emitted PUPs at all.
> 
>    Noel
> 
> PS: It's mildly irritating that Wikipedia credits Yeager for being "the
> inventor of a packet-switched, "Ships in the Night", multiple-protocol
> router". It was true independent co-invention; I don't think either one of us
> had heard a word of what the other was doing.
> -- 
> Internet-history mailing list
> Internet-history at elists.isoc.org
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There are a couple of links to network implementation notes on the following page that mention your PUP work and other MIT campus networking activities during 1980.  See NINs #25 and #33.  I thought other ih list members would find this interesting.

https://web.mit.edu/~saltzer/www/publications/memos.html

—gregbo