[ih] Installed base momentum (was Re: Design choices in SMTP)

[John Day]

Sorry just catching up on this.

Glad you brought up congestion control again. From what I know of the history, it goes like this:

The first discussion of congestion control for networks and what was later called datagram networks is in a proposal by Donald Davies in 1966.

The CYCLADES group immediately recognized the problem when they applied datagrams with end-to-end transport in 1972 and initiated a contract with the University of Waterloo to investigate it. Merek Irland, a brilliant young grad student at Waterloo undertook the Work as his PhD thesis. There are early results in the 4th DataComm Symposium and two papers in the Symposium on Flow Control in Computer Networks held in 1979 at Versailles. Unfortunately, Irland’s work was lost until recently due to unfortunate events: the shutdown of CYCLADES and Irland’s death. (The 1979 symposium is dedicated to him.) I accidentally found out about it and tracked it down. Most of the results are in the thesis.

The ARPANET team under Dave Walden was very much aware of the issue and went to great lengths in the IMP subnet to avoid it. This was helped by the fact that in the early ’Net, with the exception of the 2 or 3 cross country links, stop-and-wait was all that could be done between IMPs. An ARPANET message (not packet) at 56Kbps was several hundred miles long.

Craig, earlier you said this:
> Nicely, the most prominent and
> complementary papers on congestion issues, one by Van Jacobson (TCP/IP) and
> one by Raj Jain and KK Ramakrishnan (DECNET),
> were presented back-to-back at the ACM SIGCOMM conference in 1988.  So if
> you were looking to build (or soon after via NSFNET, connect
> to) a sturdy wide-area network, unless you were a DEC VMS organization,
> your best choice was TCP/IP.

Were you implying that Jain’s work was unique to DECNET?  I have read both work carefully and I didn’t see anything in Jain’s report that was unique to DECNET.  And I have to say that the 4 parts of report of Jain’s team is some of the finest computer science research I have ever seen. I wish we saw more of it.

Take care,
John

> On Feb 13, 2023, at 15:44, Jack Haverty via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> It seems that I didn't receive some messages over the weekend....sorry if anyone has already noted what I say below.
> 
> Re the ARPANET and Congestion Control:   This was definitely a hot topic, in particular after DCA took over operations and the network grew in size.   There were DCA-managed contracts to rework the internal mechanisms of the ARPANET to handle the much larger and diverse networks of IMPs that evolved into the multiple IMP-based networks called the DDN.   Congestion control was just one issue of several that interacted, e.g., routing, flow control, retransmission, buffer management, etc.  The IMP design, although a "packet network", in effect had a "serial byte stream" mechanism internally to make sure all data got from source host to destination.  The ARPANET had the equivalent of parts of a TCP built inside the IMPs to guarantee the delivery of a data stream.
> 
> I'm not sure how much historical detail you'll find in traditionally published papers and journals.   Outside of academia that wasn't a priority.  But there were extensive and detailed reports prepared as part of the ARPANET "operations" contracts and delivered to DCA. Here's one 3-volume, multi-year example that discusses a lot of the work in the early 80s on "congestion control" and new internal IMP mechanisms in general:
> 
> https://apps.dtic.mil/sti/citations/ADA053450
> https://apps.dtic.mil/sti/citations/ADA086338
> https://apps.dtic.mil/sti/citations/ADA121350
> 
> There's hundreds of pages of detail in those reports and there are others available through DTiC.   I was listed as author on some of these, because at the time that contract was one of "my" contracts -- which meant that I had to make sure that the report got written and delivered so we would get paid.   I didn't personally work on the ARPANET technical research, but I did absorb some understanding of the issues and details.  The "IMP Group" was literally just down the hall.
> 
> At the time (early 1980s), I was involved in the early Internet work, when TCP/IP V4 was being created and the various flow and congestion control mechanisms were being defined.  From the ARPANET experience, it was clear to me that the IMP gurus "down the hall" at BBN viewed congestion control as a major issue, and that sometimes surfaced as statements such as "TCP will never work".  TCP didn't address any of the issues of congestion, except by the rudimentary and unproven mechanism of "Source Quench".
> 
> The expectation was that the Internet would work if congestion was avoided rather than controlled, which could be attempted by keeping network capacity above traffic demands, at least long enough that TCP's retransmission and backoff mechanisms in the hosts would throttle down as expected to match what the network substrate was capable of carrying at the time.   Of course those mechanisms were now distributed among the several hosts and network switches (e.g., IMPs, Packet Radios, computer OS, gateways) involved, designed, built, and managed by different organizaions, which made it challenging to predict how it would all behave.
> 
> Even today, as an end user, I can't tell if "congestion control" is implemented and working well, or if congestion is just mostly being avoided by deployment of lots of fiber and lots of buffer memory in all the switching locations where congestion might be expected. That of course results in the phenomenon of "buffer bloat".   That's another question for the Historians.  Has "Congestion Control" in the Internet been solved?  Or avoided?
> 
> Jack Haverty
> 
> 
> 
> On 2/13/23 08:19, Craig Partridge via Internet-history wrote:
>> On Sat, Feb 11, 2023 at 7:48 AM Noel Chiappa via Internet-history <
>> internet-history at elists.isoc.org> wrote:
>> 
>>> 
>>>     > From: Craig Partridge
>>> 
>>>     > We figured out congestion collapse well enough for the time
>>> 
>>> It should be remembered that the ARPANET people (hi!) had perhaps solved
>>> this
>>> problem a long time before. I'm trying to remember how explicitly they saw
>>> this as a separate problem from the issue of running out of buffer space
>>> for
>>> message re-assembly at the destination IMP, but I seem to recall that RFNMs
>>> were seen as a needed throttle to prevent the network as a whole from being
>>> overrun (i.e. what we now think of as 'congestion', although IIRC that term
>>> wasn't used then), as well as flow control to the source host (as we would
>>> now call it).
>>> 
>>> I don't recall exactly where I saw that, but I'd try the BBN proposal to
>>> DARPA's RFP, and the first JFIPS paper ("The interface message processor
>>> for
>>> the ARPA computer network").
>>> 
>> I don't recall the details either, though I remember stories of Bob Kahn
>> going to LA to beat up on the first few ARPANET nodes
>> because he anticipated various issues, I think including congestion.  And
>> he found them and fixes were made.
>> 
>> But remember ARPANET was homogeneous -- same speed for each link and a
>> single control mechanism.  I think John Nagle was
>> the first to point out ("On packet switches with infinite storage") that
>> connecting very different networks had its own challenges.
>> And to my point, not something that a person working with X.25 would have
>> understood terribly well (yes X.75 gateways existed but
>> they typically throttled the window size to 2 packets, which hid a lot of
>> issues).
>> 
>> Craig
> 
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