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From: tcp-ip@ucbvax.ARPA
Newsgroups: fa.tcp-ip
Subject: Re:  Problems with ACC's LHDH/ECU HOST/IMP interfaces?
Message-ID: <9501@ucbvax.ARPA>
Date: Wed, 31-Jul-85 05:29:18 EDT
Article-I.D.: ucbvax.9501
Posted: Wed Jul 31 05:29:18 1985
Date-Received: Fri, 2-Aug-85 00:31:03 EDT
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Organization: University of California at Berkeley
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From: Mike Muuss <mike@BRL.ARPA>

We have about 8 ECU links here, and no trouble that can't be cleared
by the RESET switch, at worst.

We run anywhere from 9600 baud to 480,000 baud, with most links
at 50,000 64,000 and 100,000 baud, and one each at 9600 and 480,000.

All operate as Distant Hosts.  Most connect to an ACC LH/DH-11,
the remainder connect to BBNCC C/70 computers.

My only observation so far is that when the 9600 baud link becomes
marginal, things work worse that I would have expected.  There may
be some timeouts in the ECUs which need tuned for link speed.

Another factor which is important:  For our hosts operating at the
end of ECU links, especially ones which go marginal, we turn off
RFNM counting in the software.  Even though TCP can handle dropped
packets, the IMP/HOST protocol (ISO layer 2) can NOT stand dropped
RFNM packets, and if this is happening to your host, it will "gum up"
and give "out of buffer space" messages.  On 4.2 BSD systems,
a "netstat -h" with values of 8 in the RFNM column indicate that
you have this problem.  I can supply C code patches for this
if you need it.
	-Mike