Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!apple!olivea!samsung!munnari.oz.au!mtiame!ubeaut!mwp
From: mwp@ubeaut.oz.au (Michael Paddon)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: TCP segment size -- user defined?
Message-ID: <264@ubeaut.oz.au>
Date: 19 Oct 90 03:19:58 GMT
References: <538@gohp3.graphon.com>
Organization: Digital Equipment Corp., Melbourne, Australia
Lines: 28

From article <538@gohp3.graphon.com>, by dc@gohp3.graphon.com (Darren Croke):
> In article <256@ubeaut.oz.au> mwp@ubeaut.oz.au (Michael Paddon) writes:
>>
>>There is not much point setting TCP_MSS to be greater than
>>	(maximum IP packet size - IP header size - TCP header size)
>>[536 octets] since IP fragmentation will take place. Receipt of a
>>fragmented packet is an all or nothing proposition; a good thing to
>>avoid for throughput reasons.
>>
> I think you will find that it is common for IP implementations to
> send and accept datagrams without fragmentation up to 
> (connected network MTU - IP header size - TCP header size).

You are, of course, correct. The link-layer MTU is the important variable
here, determining the maximum size of datagrams (up to 64K octets).

I pulled the value 536 from some work I was doing with a SLIP implementation,
forgetting at the time that it was a special case.

					Michael

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