Re: MTUs on different paths
Steve Deering <deering@pescadero.stanford.edu> Mon, 11 December 1989 11:17 UTC
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Date: Mon, 11 Dec 1989 02:53:00 -0000
From: Steve Deering <deering@pescadero.stanford.edu>
Subject: Re: MTUs on different paths
To: art@sage.acc.com
Cc: mtudwg
Message-Id: <89/12/11
In-Reply-To: art's message of 10 Dec 89 210000 PST
> I hadn't seen anyone point out an obvious point, so I thought that > I'd add it to the discussion. > > Not only can the MTUs in both directions differ (because of asymetric > paths), but the MTUs between a pair of hosts can potentially depend > on TOS, precedence, and/or policy if any of these ever gets > implemented. You are right that it hasn't come up in the discussions, but it is mentioned in both of the written proposals: in the second paragraph on page 6 of RFC-1063, and in the last paragraph on page 6 of my draft RFC. There is, however, a problem with the RFC-1063 approach of allowing the Reply MTU to be piggybacked on any returning datagram -- the association between the MTU and its corresponding TOS or other route-influencing options may be lost. This leads me to suggest that there are only three reasonable ways of returning MTU information to a host: (1) in an ICMP message, with the header of the MTU-seeking datagram included. (2) in an IP or higher-layer option attached to a higher-layer acknowledgement of an MTU-seeking datagram. (3) in an IP option that contains *all* of the relevent information (TOS, security, etc.), attached to any datagram returning to the source of an MTU-seeking datagram. Steve
- MTUs on different paths art
- Re: MTUs on different paths Steve Deering
- re: MTUs on different paths Craig Partridge
- Re: MTUs on different paths Steve Deering
- Re: MTUs on different paths Philippe Prindeville