Re: Poor performance related to egp?


Bob Braden (braden@isi.edu)
Fri, 31 Oct 86 10:04:19 PST


The examples you cite of "horrible" EGP routing are probably due to the
extra-hop problem in the core. Apparently we have not done an adequate
job of information-spreading, if you are not aware of this problem. I
seem to recall a blaze of messages on this very subject within the past 6
months, probably on the tcp-ip list. It began with a complaint almost
identical to yours, and ended with a scholarly explanation of the
extra-hop problem by Dave Mills.

The extra-hop problem can at worst double the core traffic, and it is
scheduled to go away when the Butterflies take over the core. I forget
the exact predicted date from BBN, but rescue is in sight.

As for performance, in some funny sense EGP is (deliberately) designed for
poor performance, in the sense that it is intended to server as a firewall
against misbehaviour by routing domains outside the core. It is true, as
Mike StJohns says, that EGP is not a routing protocol; it is also true that
this fact has led to serious restrictions in topology and therefore a
crash effort is being mounted to replace EGP with a routing protocol, under
the direction of the INENG and INARCH task forces.

However, maybe we are asking too much of EGP. Perhaps we are trying to
make it a technical fix for administrative problems. To avoid bad things
like oscillations and routing loops in the face of the "diversity" (to
use a nice word) of the Internet as a whole, EGP or whatever replaces it
will always have to use long time constants and provide some sub-optimal
routes. At the present time, the Internet is growing largely by
accretion of new Autonomous Systems, and this must lead to some
degradation as you cross boundaries. If we want better overall
performance, we need to persuade these systems to aggregate into bigger
systems, each run by centralized and professional Internet management,
and each using a carefully-optimized IGP.

I go into all this polemic, because lately I have been exposed to an
awful lot of technological optimism (ask NASA about that!) about
Internetting. I wish we could convince some of the new players in the
Internet game that it takes great technical sophistication and wisdom
to make this stuff work well. The Anarchy Model of Internetting,
while theoretically feasible due to EGP, is not really a very wise way
to go.

Bob Braden



This archive was generated by hypermail 2.0b3 on Thu Mar 09 2000 - 14:36:58 GMT