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From: randy@mc0.UUCP (randy nerwick)
Newsgroups: net.lan
Subject: Sun TCP bug (huge window)
Message-ID: <225@mc0.UUCP>
Date: Fri, 21-Mar-86 20:11:20 EST
Article-I.D.: mc0.225
Posted: Fri Mar 21 20:11:20 1986
Date-Received: Tue, 25-Mar-86 03:15:49 EST
Reply-To: randy@mc0.UUCP (randy nerwick)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 24

We have a Sun 2/170 running 2.2 equipped with a Sun ethernet board which
seems to have a problem when receiving a stream of packets from another
machine.  The advertised window becomes very large (> 60000) about the
same time a packet is missed.  The window starts out at 2048 and usually
decreases before becoming large.  The Sun also occasionally misses packets
and sets the window to zero well before the window has been filled.  

The problem originally showed up as very poor throughput while running
performance tests.  With a Sun 2/170 running 1.4 and a 3Com ethernet board
transmitting a stream of 1000 messages of a fixed size to the Sun running
2.2, many re-transmissions were occurring at small message sizes, particularly
128 byte messages.  The problem also showed up with larger sized messages
which were split into a combination of large and small packets for
transmission.

The problem also shows up with a Vax 750 running VMS 4.1 and an Excelan TCP/IP
package transmitting to the Sun running 2.2, although the throughput is
affected much less than with the two Suns.  We have seen the same problem
with a Sun 2/160 running 2.0 receiving from the Sun running 1.4.

Has anyone else observed these problems?
-- 
Randy Nerwick
Uucp: {sdcrdcf,ihnp4,bellcore}!psivax!mc0!randy