[ih] Exterior Gateway Protocol

Wed Sep 2 15:08:36 PDT 2020

gents, in the midst of this EGP/IGP/BGP recollectioning:

where did/does SFP fit in with gateway protocol historying?
geoff

On Wed, Sep 2, 2020 at 11:10 AM 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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Geoff.Goodfellow at iconia.com
living as The Truth is True