DELNI Strangeness

Clive Dawson (AI.CLIVE@MCC.COM)
Wed 10 Sep 86 14:51:05-CDT

Here's a bit of info to add to the general folklore:

We moved to a new building last week, and after putting everything back
together, we found that TELNET connections from our Sun workstations
to our DEC-20 (they're on separate Ethernets, gateway is a Sun) were
suffering from horribly poor throughput. Echo delays ranged from 1 to 10
seconds, with no load to speak of on any of the systems or the nets.

After being stumped for a couple of days, we finally realized that the only
thing that had changed was that the Sun gateway and the DEC-20 were now
sharing the same DELNI, whereas before they had been on two different
DELNIs. We made a quick switch and put the Sun onto its own transceiver
two meters away from the DELNI's transceiver. The results were immediate
and dramatic. Echoing delays disappeared completely and users were once
again happy.

Now the obvious question:

Does anybody have an explanation? Is there something fundamentally
different about intra-DELNI communication that could cause such
enormous performance problems?



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