Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!ucsd!orion.oac.uci.edu!mothra.nts.uci.edu!meggers
From: meggers@mothra.nts.uci.edu (Mark Eggers)
Newsgroups: comp.protocols.tcp-ip.ibmpc
Subject: maxseg in NCSA / CUTCP
Keywords: fragmentation - reassembly
Message-ID: <26CC5A27.25268@orion.oac.uci.edu>
Date: 17 Aug 90 20:57:11 GMT
Distribution: comp
Lines: 25

I am trying to run CUTCP or NCSA Telnet from the 'downstream' side of PC-Route
2.1.  Since these PD telnets do not do tcp reassembly, I have set up the
following in config.tel

mtu=576
maxseg=512

This should assure me that no fragmentation occurs.  However, when I connect
to a Sparc running 4.03c, this is what happens:

 0.00 TCP from 128.200.35.2.3602 to mothra.nts.uci.edu.telnet seq 612000, SYN,
window 4096, <mss 1024>
 0.01 TCP from mothra.nts.uci.edu.telnet to 128.200.35.2.3602 seq 100A7200, ack
612001, SYN,  window 4096, <mss 1024>

128.200.35.2 is the PC, and mothra.nts.uci.edu is the Sparc.  Both sides are
using an mss of 1024, which will be fragmented by the 19200 SL/IP link
running between the two PC-Route routers.

How can I prevent this fragmentation??

BTW - PC/IP from FTP software performs flawlessly in the same setup, so at
least the routing is set up properly.

thanks - /mde/