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From: geof@apolling.UUCP.UUCP
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Re: IP Datagram sizes
Message-ID: <8705261808.AA01614@apolling.imagen.uucp>
Date: Tue, 26-May-87 14:08:01 EDT
Article-I.D.: apolling.8705261808.AA01614
Posted: Tue May 26 14:08:01 1987
Date-Received: Wed, 27-May-87 05:18:35 EDT
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 >      Ideally, one would look for a "type of service" routing capability which
 >      could avoid fragmentation - rather than having to construct a path by
 >      trial and error .... 

True, although you'd need more than one bit to describe the service you want.
The desired negotiation (repeated constantly, since routes may change) is:

        tcp: I want to use N bytes per packet on this connection
        network: I can send M bytes, M<N, without fragmenting
        tcp: OK, then I'll use M bytes per packet.

If there were an IP "MTU" option that is filled in by BOTH tcp's for EVERY
packet, and modified to the min(myMTU, packetMTU) by each gateway, the problem
would be solved, since the local network layer could cache M on a per-host basis.
Hmm... I guess that you could have each TCP generate the option only when it
saw packets that were fragmented (although you wouldn't ever find out that the
MTU has increased).

I wonder how that unbends the gateways?

- Geof