PSN 7.0 and NSFnet Gateways

Lars Poulsen (lars@ACC-SB-UNIX.ARPA)
Tue, 13 Oct 87 14:26:15 PDT

With the deployment of PSN 7.0 now under way, a few X.25
sites have reported performance problems, and more may
follow as the network changes to the new end-to-end module.
Since most of the X.25 sites are connected using ACC
products, any such problems are of concern to ACC.

It is our understanding that the problems seen so far are of
two kinds:

(1) Throughput drops for some very few hosts with very high
     traffic load. This has been attributed to a buffer
     shortage in the CMU-14 node and an error (now
     corrected) in the "routing patch" code. This problem
     will disappear when the network goes to PSN 7.1.

(2) A shortage of virtual circuits between X.25 hosts and
     the PSN. This seems to only affect a few gateway hosts
     with many EGP peers. BBN has suggested more aggressive
     reclaiming of idle virtual circuits; this can be done
     either in the PSN or the host code. However, it may not
     help if the gateway's routing daemon polls its peers at
     fixed intervals: all the virtual circuits will then be
     needed at the same time.

The goal of this conversion is to provide higher throughput,
and this will be to everyone's advantage. Individual sites
that suffer the opposite effect may want to contact ACC's
customer service to enquire about the availability of a
product update which addresses the throughput issue from
another angle by using larger packet sizes and larger packet
windows. Like all of our product updates, this is free to
customers under service contract, and available for a
nominal fee to others.

Lars Poulsen, ACC Customer Service

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