Re: odd routings


J. Noel Chiappa (JNC@XX.LCS.MIT.EDU)
Fri 3 Oct 86 01:48:28-EDT


        I have a few quick comments on some recent messages; I'm going
to be a good citizen and package them togther in one reply!

        1) The extra hop problem in EGP. (Enter broken record mode.) I've
explained this several times, but let me try again quickly. This is a
problem with *GGP* (NOT EGP), the routing protocol run between the core
gateways. It was designed before EGP, and thus does not interoperate
correctly with it. If MIT has core gateway A as an EGP peer, and Rutgers
has a peer core gateway B, then there is no way (using GGP) for A to
inform B that to get to MIT it can go direct; both B and all its clients
(e.g. Rutgers) think they have to go through A. This is the cause of the
funny routes with routes to CMU, MIT, etc. Your gateway is just fine, and
it's not EGP's fault either. (Leave broken record mode.) The extra hop
problem will only be solved when GGP is retired; i.e. when the PDP11 core
gateways are replaced by Butterflys, probably. The extra hops probably are
a significant gratuitous strain on the system.

        B) Ping wars between gateways might be causing problems if BBN
never installed the patch to add more connection blocks (don't worry if
you know what this is), but if that patch is in it shouldn't be a problem.
Can anyone from BBN clue us in? I saw a note in a recent message from BBN
which talked about installing a 'performance improvement' patch to help
with the recent problems; are they referring to the increased number of
connections blocks? If not, what?

        C) "Mail's the culprit." One thought at MIT was that mail was
responsible for the bulk of our outgoing traffic. Measurements of a day's
traffic indicated that SMTP accounted for 35% of the packets and only 27%
of the data through the gateway. (These numbers do not count all traffic
from the MIT complex, since some of our biggest timesharing machines are
on the ARPANet directly, and these figures count only traffic from the MIT
net. The traffic mix on the timesharing hosts might include more mail,
which would bias the whole figure.) Still, these numbers are a long way
from indicting Mail as the culprit in the congestion. Does anyone else
have any numbers on traffic breakdown by types?

        Noel
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