Re: routing protocols will provide path-MTU
jnc@PTT.LCS.MIT.EDU (Noel Chiappa) Tue, 27 February 1990 16:46 UTC
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Date: Tue, 27 Feb 1990 11:45:56 -0500
From: jnc@PTT.LCS.MIT.EDU
Message-Id: <9002271645.AA00908@PTT.LCS.MIT.EDU>
To: deering@pescadero.stanford.edu
Subject: Re: routing protocols will provide path-MTU
Cc: mtudwg
Steve, here in the future we won't have routing 'tables' (or anything like what people now think of as 'updates') any more. What will be distributed are maps of the network, which allows entities to compute routes using whatever special criteria and algorithms they feel like using. Boxes which do routing will compute routes on demand, during a flow setup phase (which will happen in parallel with sending the first packet), and will keep a cache of recently used source-destination-TOS-etc tuples. Moreover, it won't be the case that a host will ask 'what is the MTU to this destination', it will ask 'can you get to this destination with an MTU of X'? A route with that MTU (if one exists) will be constructed on demand (much as trucks with large objects on them may take special routes now). Alternatively, you could ask 'what is the MTU of the path with the lowest $ cost', or something similar. So, given this view, it is reasonable to suspect that this mechanism will not have an infinite life, but probably (!!) wiil be superseded after some years. It is thus reasonable to take the position that it is not necessary to be absolutely on target (I know this is asking for something to happen to make a liar out of me :-). If it's not criticial, I'd like to see a final decision taken about what mechanism to use and get on with writing! We do seem to be going around in circles a bit... Noel PS: With regard to using a bit (as opposed to an option); there was some talk at one point of a general 'path attribute discovery' mechanism. I suggested then that the option have a format which would allow other things to be added later, but that we stick to MTU for now. Using the bit of course makes this impossible. (I'm still not convinced the overhead of the option is all that bad if you only send it every 100 packets or so. :-)
- routing protocols will provide path-MTU Craig Partridge
- Re: routing protocols will provide path-MTU Steve Deering
- Re: routing protocols will provide path-MTU Noel Chiappa
- Re: routing protocols will provide path-MTU Steve Deering