Re: which protocols does MTUD help?
William Westfield <BILLW@MATHOM.CISCO.COM> Fri, 01 December 1989 13:42 UTC
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Date: Fri 1 Dec 89 05:41:57-PST
From: William Westfield <BILLW@MATHOM.CISCO.COM>
Subject: Re: which protocols does MTUD help?
Cc: craig@NNSC.NSF.NET, mtudwg
In a bridged environment between FDDI and ETHERNet, the systems will normally assume that the MTU of the connected interface. The FDDI system would try to send 4k datagrams (or whatever), and these would break at the bridge (it not knowing how to fragment). MTU discovery might be able to let both systems know more about the world. (Mind you, Im not sure how, since the bridge is supposed to be invisible.) I think the usual case of this is handled by the way the MSS option works NOW (most systems advertise their interface MTU, and refuse to send a datagram larger than that even if the other host claims that it is willing to accept it). Something new might be needed to handle the case where the FDDI-ETHER bridge is on some network at an intermediate point in the path. Bill W -------