EGP, extra hop, and peers (was: TN3270)


Mike Brescia (brescia@CCV.BBN.COM)
Thu, 04 Jun 87 10:32:01 -0400


>the network is still sensitive to increased traffic on key paths.
     Has anyone ever looked into the way EGP traffic (and the "extra hop"
     problem that goes with it) effects this?

There are two factors Tom asks about. 1) the EGP protocol routing overhead
2) the "extra hop problem"

For the first, yes, every gateway is pinging 2 or 3 egp core servers every 30
or 60 seconds, and polling for routing information every 2 (or more) minutes.
We recommended earlier that implementers lengthen the times to 60 seconds and
3 minutes. This suggestion was sent out to 'egp-people' list on March 3 and
again on May 18.

For the extra hop problem, we have been recommending that EGP connections be
maintained with 2 of the 3 servers, so that for any net you try to reach will
be known directly to you because both parties are likely to be doing EGP with
the same core server, and the direct route to the other net will be advertized
to you in the EGP net-reachability (NR) message. While your gateway is
not doing EGP with that other gateway, the information is relayed by the core,
and the user traffic is not expected to pass through the core gateway.

There is an extra hop problem when you are trying to reach a local (EGP
advertized) net on the MILNET (or if you are on the MILNET side, you are
trying to reach a local net attaced to the ARPANET). This is more properly
described as a GGP extra hop problem, rather than an EGP one.

     Does anyone have any information on numbers and locations of sites
     peering with each server?

I am sending a snapshot of the routing to Tom Narten. If you want a copy too,
send me a note. It's about 4 pages.

     Would it help to skew the peering so that sites on the east peered with
     bbnnet2, and so on...

This only helps distribute the EGP protocol traffic. We think we can handle
the 60 packets a minute.

     In looking at routing tables gotten via EGP from purdue-cs-gw.arpa,
     only a handful (less than 40 out of 240) of the routes actually go
     through those [core] gateways.

You should be able to get good (ARPANET) routes directly from the EGP. ICMP
redirect will not help unless you are a host instead of (in addition to) a
gateway.

Mike

p.s.: Apologies to those on EGP-PEOPLE mailing list who get two copies. The
distributed mail data base is not yet capable of doing
( TCP-IP | EGP-PEOPLE ) /* c syntax instead of sql :-*/



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