[ih] Exterior Gateway Protocol
Jack Haverty
jack at 3kitty.org
Wed Sep 2 10:46:14 PDT 2020
Bob never mentioned why he wanted to have gateways from different
sources, so I'm not sure if the DoD evolution was the driver.
At the time, there were a lot of people/groups fascinated by the
problems inherent in routing protocols, and each wanted to try out their
ideas. I think this interest was heightened by the experience in the
ARPANET, where othes' ideas could not be put into code except by BBN,
whose focus was on running a reliable decade-old ARPANET, rather than a
research testbed for new unproven ideas from the community.
So there was a motivation to "open up" the relatively new gateway
environment in order to promote research and experimentation. That
was the task that Eric and I tackled - with the solution we settled on
being to create a "firewall" mechanism for the gateways so that such
experimentation could happen while maintaining reliability in the "core"
service.
I've always wondered why there was such fascination in the network
community with routing, yet very little interest in other areas, e.g.,
congestion control or operational issues such as problem isolation,
introduction of new releases, etc. Lots of ideas about how to do
routing better.
IIRC, one of the hot topics at the time was how to deal with operational
problems caused by research activities. There was a real desire to
start getting the Internet to stabilize as a reliable communications
service (probably motivated by DoD needs). It had to be as reliable as
the ARPANET had become by then.
Also, IIRC at the time DoD preferred multiple-source solutions, and
"COTS" (Commercial Off The Shelf) was a popular buzzword. So for TCP
to fit well into the DoD world, a single-source gateway was probably not
enough. Sole-source justifications were becoming increasingly difficult.
So, research collided with operations. Dave Mills, for example, was
famous for trying things out on the Internet that should have worked,
but didn't, and brought down some aspect of the core service. His
(research) attitude was "Let's see what happens if I do this", where our
BBN (operational) attitude was "Don't do that!".
My assumption was that Bob was searching for a way to enable research
and operational activities to coexist peacefully in The Internet. Like
all good managers, he delegated that problem, while hanging on that
subway strap.
/Jack
On 9/2/20 9:59 AM, Craig Partridge wrote:
> EGP preceded NSFnet by about 5 years (RFC 827 was released in October
> 1982). CSNET was nascent and IP service on CSNET was still a year or
> so in the future.
>
> Could Bob have been thinking about splitting off DoD IP networks to
> another provider (e.g. the logical step after inserting the
> mailbridges) and using EGP for that purpose?
>
> Craig
>
> On Wed, Sep 2, 2020 at 10:39 AM Jack Haverty via Internet-history
> <internet-history at elists.isoc.org
> <mailto:internet-history at elists.isoc.org>> wrote:
>
> Hi Dan,
>
> Re: the creation of EGP: Five or ten years ago, I summarized the
> events around the creation of EGP on this list (actually the list when
> it was hosted at ISI). You may be able to find it in old
> internet-history message archives.
>
> Here's what I wrote. The "Bob" is Bob Kahn, who was one of the ARPA
> Program Managers at the time. These events occurred just prior to RFC
> 827, sometime in 1981/2:
>
> > I was at one of innumerable meetings. Sorry, I can't remember where
> or when.
> > It was probably in DC, where I spent a lot of time, but my gut
> feeling
> tells me
> > it was the European Internet meeting, maybe in Munich.
> Anyway,... Bob
> and I
> > were hanging on the same subway strap, with the usual group of a
> dozen
> or two
> > people heading out to find dinner. Bob wanted to talk about the
> Internet
> > architecture, and in particular the core gateways. He managed
> over the
> > squealing of the car's wheels to overcome my skepticism and make it
> clear that
> > it would be a good idea to figure out how to make it possible for
> gateways not
> > built by BBN to be full participants in the system of gateways. I
> don't know
> > whether this was motivated by political pressures to enable
> CSNET/NSFNET, or
> > some technical considerations, or by the ARPA charter to focus
> on new
> technology
> > and new ideas, rather than replicating the old ones. But he
> convinced
> me, and I
> > went away with a new direction, and a harder task to make something
> work using
> > an unproven approach.
> >
> > Back at BBN, the challenge was not only to figure out how to make a
> stable
> > heterogeneous Internet, but also how to convince the people on the
> project that
> > it was a good idea to let other people build gateways and hook
> them up
> to "our"
> > system. Fortunately the meetings of the TCP and IP working groups
> were great
> > training for this kind of work. I recruited one of the best
> thinkers
> from the
> > ARPANet crowd - Dr. Eric Rosen. He and I sat down for several
> multi-hour
> > brainstorming sessions, and came up with the notion of "autonomous
> systems",
> > which were sets of routers owned/managed by a single
> organization, and
> > interconnected with other such systems to form the overall
> Internet.
> EGP (which
> > I think evolved into BGP) and the concept of IGP (which basically
> means whatever
> > mechanisms are used among the routers inside their own closed
> system)
> made it
> > possible to use different approaches within different ASes.
> This led
> to RFC
> > 827 and a bunch of others in the early 80s.
> >
>
> IMHO, it's important to note that we defined EGP *not* as a general
> purpose routing protocol, but rather as a "firewall" mechanism, which
> would permit different internal mechanisms (IGPs) to be introduced
> into
> the Internet, each isolated in its own "autonomous system". This is
> described in RFC 827. If a particular AS wanted to protect
> itself, it
> could design its own IGP to be "skeptical" of routing information it
> received from other ASes through the EGP interactions. EGP was not
> intended to "solve the problem". It's purpose was to create an
> experimental testbed in which various ideas could be tried to find
> good
> answers.
>
> So, the purpose of EGP was to make it possible for diverse groups
> to try
> out their ideas in the operational Internet, in their own AS, and
> retaining the possibility of isolation between different ASes so that
> flaws in one could be prevented from causing outages elsewhere. That
> of course depended on exactly what mechanisms each group
> implemented in
> their own internal IGP mechanisms to provide such isolation. For
> example, an AS might choose to ignore routing information from another
> AS claiming a "better" route to some network that the AS itself has a
> route to reach totally within that AS.
>
> In particular, Eric continued that work and wrote a series of internal
> BBN documents about ideas for the IGP to be used in the "core
> gateways"
> AS, which BBN was tasked to operate as a reliable 24x7 core Internet
> service.
>
> I don't know if that BBN IGP ever got implemented in the core
> gateways. Other groups doing gateways (Dave Mills' et al, the MIT
> group, Cisco, etc.) presumably did their own IGPs, but I never heard
> much about anyone's IGP design or implementation.
>
> /Jack Haverty
>
>
> On 9/2/20 6:55 AM, Dan York via Internet-history wrote:
> > Grant,
> >
> > On Sep 1, 2020, at 11:24 PM, Grant Taylor via Internet-history
> <internet-history at elists.isoc.org
> <mailto:internet-history at elists.isoc.org><mailto:internet-history at elists.isoc.org
> <mailto:internet-history at elists.isoc.org>>> wrote:
> >
> > Does anyone know of any surviving implementations of Exterior
> Gateway Protocol, BGP's predecessor.
> >
> > I know that NetWare 4.x has an implementation of EGP. But I'm
> not aware of anything else that did support it. I assume that
> Cisco IOS of the time did. Did any other network operating system
> vendor or 3rd party vendor have EGP implementations?
> >
> > I have no knowledge of EGP implementations … but related to EGP,
> one of my personal late night hobbies/distractions during the
> pandemic has been diving more deeply into Wikipedia editing, and I
> noticed that the page for EGP needs some citations / references:
> >
> > https://en.wikipedia.org/wiki/Exterior_Gateway_Protocol
> >
> > 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.)
> >
> > 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.
> >
> > (Note that for info to appear in the English version of
> Wikipedia, it needs to be backed up by a “reliable source” -
> https://en.wikipedia.org/wiki/Wikipedia:Reliable_sources - which
> includes journal articles, academic papers, news articles, RFCs, etc.)
> >
> > Dan
> >
> > P.S. Please do note that this Wikipedia updating is something I
> do on my own personal time and is not part of any of my
> responsibilities and work at the Internet Society. This is just me
> wanting to update info in Wikipedia to be more accurate. :-)
> >
>
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