Path: utzoo!censor!geac!lethe!tvcent!comspec!telly!attcan!uunet!maverick.ksu.ksu.edu!hoss!sardion!mosemann
From: mosemann@sardion.unl.edu (Russell Mosemann)
Newsgroups: comp.sys.mac.comm
Subject: MacTCP has bad segment size
Summary: MacTCP determines wrong maximum segment size, what is fix?
Keywords: MacTCP maximum segment size error
Message-ID: <1991Mar26.213034.8544@hoss.unl.edu>
Date: 26 Mar 91 21:30:34 GMT
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Reply-To: mosemann@unl.edu
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Organization: University of Nebraska - Lincoln
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   Weeks and weeks ago, people were discussing the problem MacTCP has
with determining the MSS (maximum segment size).  I read the messages
but never wrote anything down or saved it because we didn't have that
problem before.
   A few weeks ago MacPOP (from trident.arc.nasa.gov) started
complaining that there was an error connecting to the POP server.  I
could telnet to the port and issue commands by hand with no problem.
Using a network sniffer, I saw the domain name request get resolved and
the Mac sent out 4 or 5 TCP packets to the POP host, but the host didn't
respond.
   I dug into the packets and found that it was requesting a window size
of *10241*.  Could someone mail the fix for this (I think it was done by
Steve Dorner)?
   What was the explanation for this?  I think it had something to do
with a device on the network advertising the wrong segment size.  If so,
is there any fix for that device besides turning it off?  The other
weird thing is that only the MacPOP software seems to be affected.  I
can telnet with TCP/Connect II and NCSA Telnet just fine.
   Thanks for the help.
--
Russell Mosemann                  Internet:             mosemann@unl.edu
Network Analyst                   Bitnet:               mosemann@unlvax1
Computing Resource Center         UUCP:   ..!uunet!hoss.unl.edu!mosemann
University of Nebraska - Lincoln  Voice:  (402) 472-5930   Fax: 472-5280