NSFNET woe: causes and consequences


mills@udel.edu
02-Oct-87 01:05:04-UT


BAD MSG:
the reasons. If I am correct, you are not going to like the consequences.
Last Thursday the primary NSFNET gateway psc-gw became increasingly flaky,
eventually to the point where it and its seventy-odd nets disappeared from EGP
updates. Backup gateways linkabit-gw and cu-arpa picked up the slack, but not
without considerable losses and delays due to congestion. When the new ARPANET
code was installed over the weekend, psc-gw and its PSN (14) both completely
expired, reportedly due to "resource shortage," the usual BBN euphemism for
insufficient storage or table overflow, especially for connection blocks which
manage ARPANET virtual circuits. Apparently, BBN backed out of the new code,
so the PSN is unchanged from Thursday.

Meanwhile, Maryland gateway terp, also connected to a PSN (20) running the new
ARPAware, began behaving badly, so much so that terp was simply turned off,
leaving another Maryland gateway to hump the load. At this time (Thursday
evening) the gateway is still off. Since both psc-gw and terp have similar
configurations, connectivity and PSN (X.25) interfaces, one would assume the
same varmit bit both of them.

Meanwhile, I was sitting off PSN 96 trying to figure out what was going on and
noticed linkabit-gw 10.0.0.111 and dcn-gw 10.2.0.96 could not reach psc-gw at
its ARPANET address 10.4.0.14. However, both of these buzzards could reach
other hosts with no problem. Furthermore, EGP updates received from the usual
corespeakers revealed psc-gw was working just fine. I concluded something
wierd was spooking the ARPANET; however, I found that cu-arpa 10.3.0.96 and
louie 10.0.0.96 could work psc-gw at its ARPANET address. I thought maybe X.25
was the key, since all of the other PSN 96 machines use 1822, and cranked up
swamp-gw 10.9.0.96 using X.25, but found no joy with psc-gw either.

When Dave O'Leary of PSC called to tell me their ACC 5250 X.25 driver for the
MicroVAX was spewing out error comments to the effect that insufficient
virtual circuits were available, all the cards fell into place. The 5250
supports a maximum of 64 virtual circuits. Apparently the number of ARPANET
gateways and other (host) clients has escalated to the point that the



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