[ih] Exterior Gateway Protocol

Wed Sep 2 14:23:02 PDT 2020

Yes. My first IETF was #3 and a major topic was "FGP", the Follow-On
Gateway Protocol, figuring out a follow-on to EGP (several people on this
list will remember that time). It didn't get far, but we tossed good ideas
around, in particular iirc Mike St. Johns wanted to eliminate using numbers
to prioritize routes in any way. When the IETF developed working groups, I
had a short-lived one named something like "Topology Engineering" that fed
into Guy's WG. The zero-one-infinity mantra, and the conceptualization of
what was eventually called path vector, were great developments.
Unfortunately I got sick just before the Austin IETF so I missed the moment
of birth of BGP but Jeff Honig was there, and we piled in with the
Gatedaemon. Dennis Ferguson (again, that's as I recall) had an
implementation for gated in ~3 weeks.  After that, when I was doing
multicast, attempts at source-asserted path vectors for interdomain
multicast came right out of those early BGP concepts.

On Wed, Sep 2, 2020 at 5:10 PM Guy Almes via Internet-history <
internet-history at elists.isoc.org> wrote:

> Craig et al.,
>    1987 was an interesting year.  The NSFnet-related regional networks
> were connecting new sites and had to solve interesting routing problems.
>    EGP would tell you that a given network was reachable via a given
> gateway router / AS.  But that network might be reachable via two
> different gateways.
>    During that era, our "Sesquinet" regional network in Texas was
> connected to two different valuable "backbone" type networks: the
> Fuzzball-based proto-NSFnet via Boulder and the ARPAnet via Austin.
> Both were useful.  Both had 56kb/s circuits.  Both were congested.
>    At that time, there were a few hundred networks, and I recall going
> through the whole list, one by one, figuring out whether, if they were
> reachable via both the ARPAnet and the proto-NSFnet, which should be
> preferred.  I considered it worth doing, but it was of course Quixotic,
> given the rapidly growing number of connected networks.
>
>    Phill Gross asked me to lead an "Interconnectivity Working Group"
> within the IETF and work to solve some of these problems.  It was a
> great group, with members from the ARPAnet, NSFnet, NASA, ESnet, and
> other communities.  Understanding the various "backbones", their
> differing technical and policy natures, and the limitations of EGP all
> made for fascinating discussions, which did allow us to make progress.
>    One of our explicit marching orders was *not* to invent a new protocol.
>    But we did discuss the problem of how to choose which of two exterior
> routes to use when both advertised a given network.
>    One line of thought was to consider that the Internet, while not
> having a "tree topology", did have a notion of levels of hierarchy,
> e.g., campus, then regional, then national backbone, then international
> links.  I am grateful that we fairly quickly realized that relying on
> that notion of hierarchy would be building on sand.
>    But what kind of "metric" could be used to help make routing decisions?
>    One idea, based on Cicso's IGRP protocol was to characterize each
> transit network with a bandwidth and a delay metric.  Then minimum of
> bandwidth along a path and sum of delay along a path could be used.
> That did not get traction.
>    I'd been teaching a computer scientist where an idea called the
> "zero, one, infinity rule" was discussed.  As applied here, if a single
> scalar number would not suffice as a metric, then allow a metric of
> variable length.  For example, a whole AS-path could be an interesting
> kind of metric could be used.  But, particularly during that era,
> variable-length fields in protocols were not in favor, and we did not
> pursue this idea.
>    Except that, at our next working group meeting (at the January 1989
> IETF meeting at UT-Austin), Kirk Lougheed (Cisco) and Yakov Rekhter
> (IBM) invented BGP in one of the Internet's most famous napkins.  The
> complete AS-path, variable though it was, was a key idea.
>    BGP solved several problems with EGP.
>    I should emphasize that the AS-path was never exactly regarded as a
> "metric", but it provided valuable information.  I'll avoid going
> further with the evolution of BGP, but it was so much better than its
> predecessor and came along at a very fortunate time.
>
>         -- Guy
>
> On 9/2/20 3:57 PM, Craig Partridge via Internet-history wrote:
> > There was a SIGCOMM '87 paper by Mills and Hans-Werner Braun that
> discussed
> > what happened when you tried to break the tree topology.
> >
> > Craig
> >
> > On Wed, Sep 2, 2020 at 1:52 PM Scott O. Bradner via Internet-history <
> > internet-history at elists.isoc.org> wrote:
> >
> >> I found a printout of my late 1990s notes which said that EGP was
> "limited
> >> to a tree structured Internet"
> >> although I recall that people were hacking it to expand its usefulness
> but
> >> the result was not pretty
> >>
> >> Scott
> >>
> >>
> >>> On Sep 2, 2020, at 3:45 PM, Barbara Denny <b_a_denny at yahoo.com> wrote:
> >>>
> >>> That is my recollection too. EGP had topology constraints.
> >>>
> >>> barbara
> >>>
> >>> On Wednesday, September 2, 2020, 08:07:37 AM PDT, Scott O. Bradner via
> >> Internet-history <internet-history at elists.isoc.org> wrote:
> >>>
> >>>
> >>> my recollection was that EGP could not be twisted enough to be able to
> >> deal with the actual
> >>> topology that was evolving on the Internet
> >>>
> >>> Scott
> >>>
> >>> ps - I tried to open an old powerpoint presentation (from the late
> >> 1990s) where I discussed EGP & BGP
> >>> but it seem like the oldest version of PowerPoint I have had evolved
> >> enough that it will no longer open
> >>> that version  - I mention that because there is yet again a discussion
> >> on the IETF list about RFC formats
> >>> and some people have argued, as people have argued for at least 20
> >> years, that moving to MS Word
> >>> would be a good thing
> >>>
> >>>
> >>>
> >>>> On Sep 2, 2020, at 10:39 AM, Grant Taylor via Internet-history <
> >> internet-history at elists.isoc.org> wrote:
> >>>>
> >>>> On 9/2/20 7:55 AM, Dan York via Internet-history wrote:
> >>>>> Grant,
> >>>>
> >>>> Hi,
> >>>>
> >>>>> It also needs more explanation that EGP was replaced by BGP. (The
> >> current sentence there says “essentially replaced” and is a bit vague
> with
> >> no references.)
> >>>>
> >>>> Hum.
> >>>>
> >>>>> If any of you all here know of any RFCs that explicitly indicate EGP
> >> was replaced/obsoleted, or if you know of any journal articles, academic
> >> papers, historical documents, etc., that could be useful, I would be
> glad
> >> to update the article a bit. Or if you can point me to any info about
> the
> >> creation of EGP (there’s a line that needs a source). Or any other info
> you
> >> think would be useful in this Wikipedia article, that would be great.
> >>>>
> >>>> I found a some information about EGP in and around the gated routing
> >> daemon.  I wonder if there might be some more information that could
> help
> >> you.
> >>>>
> >>>>> (Note that for info to appear in the English version of Wikipedia, it
> >> needs to be backed up by a “reliable source” -
> >>
> https://urldefense.com/v3/__https://en.wikipedia.org/wiki/Wikipedia:Reliable_sources__;!!KwNVnqRv!VGbu8UR1ds9tLcdTmqj_BlSaJwdAR7VMX3YliVLEE7V0gQyXuH0Pp6ld3QEI5A$
> - which includes
> >> journal articles, academic papers, news articles, RFCs, etc.)
> >>>>
> >>>> I wonder if you can find any graphs on the number of Internet
> >> connections using BGP.  If similar ever existed for EGP, you can
> probably
> >> compare / contrast the two.
> >>>>
> >>>> I also think that the lack of contemporary EGP implementations is
> >> evidence of BGP's replacement of EGP.  As is the fact that BGP supports
> >> things that EGP does not.  Things which are used all over the Internet,
> >> e.g. multipath.
> >>>>
> >>>>
> >>>>
> >>>> --
> >>>> Grant. . . .
> >>>> unix || die
> >>>>
> >>>> --
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> >>>> Internet-history at elists.isoc.org
> >>>>
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> >>>
> >>>
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> >>>
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> >>
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> >>
> >
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