Subject: [SIP] Reliable provisional responses

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 19 Jun 2000 00:16:07 -0400

Folks,

WG last call has pretty much ended on the reliable provisional responses
draft. The only open issue seems to be whether prack should be
cumulative or not. There was one note arguing against it, and I weakly
argued in favor of it. To follow a recent trend I seem to be having
regarding about-faces, I think I have changed my mind on this one too.

Why? Cumulative prack is purely an optimization; you can always send N
separate PRACKs instead of a single cumulative PRACK. The reduction in
messaging is the only benefit; it is still possible to support multiple
outstanding reliable provisional responses without cumulative PRACK. The
primary drawback is complexity. One of the ones which concerns me is
determining the set of outstanding reliable provisionals covered by
prack. If people place the reliable provisional state machine objects
into a hash table, indexed by, among other things, the rseq number, this
makes it hard to match up transactions with PRACK. Finding the a set of
things matching a rule, where those things are stored in a hash table,
is a pain. 

So, given that (1) we have no specific application which really is a
killer app for cumulative PRACK, (2) its a message reduction
optimization for something which is probably not a common case, and (3)
there are complexity issues that make an implementation difficult, I am
proposing to remove this feature from the spec before submitting the
version that will go to IESG.

So, if you want to speak in favor of keeping this feature, speak NOW
(well, within 3 days, say), or forever hold your peace....

-Jonathan R.
-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (732) 741-7244
http://www.dynamicsoft.com

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