Re: Core gateway slot problem

4 Apr 1986 13:29:09 EST

In response to the message sent Fri 4 Apr 86 00:14:07-EST from sy.Ken@CU20B.COLUMBIA.EDU


I suspect BBN warriors may be too bloodied and weary to have announced
a damage report, so please treat the following as an unofficial summary.
When the core tables were expanded over 128 nets at least two bugs developed
which reesulted in broken, oscillating routes within the core system. The
problems then led to massive surges in gateway control traffic, as well as
massive surges in redirects, not to mention aimlessly wandering datagrams
carrying possibly useful user traffic. The situation became acute about
a week ago, since when BBN has been feverishly updating all the core gateways,
some of which are fiendishly hard to update (bubble memories, etc.). In the
last couple of days things have improved, which is a good sign.

The evidence is not hard to detect upon inspection of the EGP hop-count
fields received by your EGP peer. You may notice the gateways wandering
about the ARPANET or MILNET, as well as the high incidence of unusually
large hop counts, not to mention the incidence of nets bobbing up and down.

I have also noticed locally a marked increase in the incidence of ARPANET
host-down messages, which may be realted to gateway reloading and
the suspected traffic surges.

My personal, unsubstantiated suspiciion suspicion is that instabilities
in the core routing system due inconsistent tables (becasue of overflow) may have
contributed significantly to the recent deterioration in performance.


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