[ih] Exterior Gateway Protocol

[Jack Haverty]

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>> 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. :-)
>