Re: quibbling with Meeting report
mogul (Jeffrey Mogul) Wed, 13 December 1989 21:37 UTC
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From: mogul (Jeffrey Mogul)
Message-Id: <8912132137.AA26146@acetes.pa.dec.com>
Date: 13 Dec 1989 1337-PST (Wednesday)
To: Craig Partridge <craig@nnsc.nsf.net>
Cc: mtudwg
Subject: Re: quibbling with Meeting report
In-Reply-To: Craig Partridge <craig@NNSC.NSF.NET> /
Wed, 13 Dec 89 08:59:50 -0500. <8912131400.AA24077@decwrl.dec.com>
But... I'd like to urge you all to reconsider the notion the MTU is stored per transport protocol. NFS *CAN* use MTU information as can most other applications if it is made available to them.... A misimpression conveyed by my summary, I guess. Senders store MTU per destination (i.e., in the IP layer). The receiver, we decided, should not send an ICMP Fragmentation Report message in reply to an NFS packet unless it has received an option from that host+port indicating that the NFS implementation ON THAT HOST is willing to do something with this ICMP. Otherwise, we are just filling the internet with useless ICMPs. Consider the case where one pair of hosts simultaneously has an NFS and a TCP connection in progress. Suppose that the receiver stored the "sent RF" per-host, rather than per-port. Then, suppose that the sender TCP is sending the RF flag (in an option or wherever) but the NFS is not (because, for whatever reason, the sender's NFS is not willing to listen to the Fragmentation Reports). Then, the receiver will continually send Frag Reports to the sender in response to NFS packets, even though (1) the sender's TCP may never cause fragmentation and (2) the sender's NFS will never do anything with these ICMPs. Wasted bandwidth. But this is an "implementation suggestion", perhaps even a "good citizen requirement", not a part of the actual protocol spec. -Jeff
- which protocols does MTUD help? Craig Partridge
- Re: which protocols does MTUD help? Jeffrey Mogul
- Re: which protocols does MTUD help? William Westfield
- Re: quibbling with Meeting report Jeffrey Mogul