Re: TCP maximum segment size determination

Philip A. Prindeville (PAP4@AI.AI.MIT.EDU)
Tue, 10 Nov 87 23:52:11 EST

My apologies if someone has already thought of this, but mail to my site is
being delayed by up to 5 days, and seems to arrive in random order. But,
here goes anyway:

    Date: Thu, 05 Nov 87 21:31:54 CST
    From: Bruce Orchard <ORCHARD/>
    Subject: TCP maximum segment size determination

    [ ... ]
    large value. Each node that transmitted the packet would compare
    the value given in the option to the maximum transmission unit of
    the outgoing network. If the network value were less, the value
    in the option would be reduced to the network value.

    [ ... ]
    One limitation of this proposal is that all packets of a TCP
    connection do not necessarily pass through the same networks.
    Actually, given the way the networks are connected, all packets
    usually go through the same networks. Also, if one packet takes a
    different route from an earlier packet, the second route could be
    on the same kind of network (for example, two parallel Ethernets).
    Regardless, the consequence of a poor choice is reduced
    throughput, not failure.

What about the required overhead for gateways and routers to have
to further inspect each packet? It could be optimized so that only TCP
packets are inspected, but still, that would seem to add to the burden of
possibly compute-bound gateways...

    P.S. Is the MTU of SATNET really 256 bytes, as given in IEN 192?

Could be worse, could be the 128 byte MTU of most X.75 implementations...


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