Subject: RE: [NSIS] comments on draft in-path and out of path (draft-schelen-nsis-opopsig-00.txt)

From: [email-masked]
Date: Fri, 5 Jul 2002 11:23:15 +0300

Hi Robert,

First off, let me say something about on-path vs. off-path signaling.
The intention of NSIS is to work on standardizing a solution for 
on-path signaling - that means the signaling follows the path 
which the data packets follow.  If there is non-standard 
routing of packets, then the signaling will follow.

Please note the Area Directors realize that off-path signaing
is interesting and may have use, but NSIS is not chartered
to do that work.  It may be possible to work on this after 
we have fulfilled our initial charter.

> I'd like to try to make one general comment about the on/off 
> path question, namely that it really needs to be carefully 
> distinguished from the question of whether protocol messages 
> are implicitly or explicitly along whatever path. The latter 
> question is really about NSIS addressing: we identified both 
> modes in our latest framework document (section 3.3.4 if 
> you're interested) and called them e2e and peer-session 
> addressing respectively. Both are applicable in the on-path 
> case; the off-path case basically requires the peer-session mode.

Agreed.

> With peer-session addressing it's clear that you need to work 
> out the address of the NSIS peer. I guess the emphasis on the 
> on-path case means that we aren't going to put a lot of 
> effort into working out the addresses of off-path peers. But 
> (personally) I'd be worried if we built assumptions about the 
> addressing model into other aspects of the protocol, and so 
> it's unfair to say that an on path protocol is fundamentally 
> unable to cope with traffic engineered networks - it's just 
> that maybe NSIS won't provide all the address discovery 
> mechanisms in this (fundamentally harder) case.

Agreed.  I think address discovery (& service discovery) are 
very difficult issues and are out of scope for NSIS.

John

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