Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!husc6!hao!ames!ucbcad!ucbvax!MONK.PROTEON.COM!jas
From: jas@MONK.PROTEON.COM (John A. Shriver)
Newsgroups: comp.protocols.tcp-ip
Subject: IP Datagram sizes
Message-ID: <8705232244.AA07675@monk.proteon.com>
Date: Sat, 23-May-87 18:44:44 EDT
Article-I.D.: monk.8705232244.AA07675
Posted: Sat May 23 18:44:44 1987
Date-Received: Sun, 24-May-87 01:32:05 EDT
References: <[G.BBN.COM]22-May-87.20:11:55.CLYNN>
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 13

Two problems with looking at incoming fragments.

1. It tells you the other guy is sending packets that are too large.

2. The TCP MSS option is only valid in SYN packets, which almost
always have no data.  You will find out too late.

Another interesting problem to think about is that the fragmentation
issue could shift dynamically as routes change.

I'd guess that the first tool would be an ICMP record MSS type, or
some IP option.  Of course, not many routers handle source routing
yet...