Re: [Sip] Congestion safety

[Dean Willis <dwillis@dynamicsoft.com>]

Ok, I think you're saying that providing 

   1) a way to detect not-congestion-safe links 
   2) pacing transmissions over not-congestion-safe 
      links so as to avoid overlap 

are an adequate solution, making

   3) Avoiding fragmentation over not-congestion-safe links 

unnecessarily complex.

Inasmuch as solving message-size issues appears to be intractable, I
concur.

Do we have consensus on this in the WG?

--
Dean


On Sat, 2002-10-26 at 06:32, Gonzalo Camarillo wrote:
> Folks,
> 
> I have been reading the two drafts we have about congestion safety.
> 
> http://www.ietf.org/internet-drafts/draft-khartabil-sip-congestionsafe-ci-01.txt
> 
> and
> 
> http://www.ietf.org/internet-drafts/draft-ietf-sip-congestsafe-00.txt
> 
> 
> I believe that trying to control the pace at which a proxy sends request
> is a good idea. Dean and Ben's draft deals with that.
> 
> In addition to that, both drafts try to deal with SIP message size. I am
> not sure that we want to go down this path. Both drafts propose
> application-layer solutions to this problem. However, the SIP layer can
> only make educated guesses about the size of a SIP message
> "on-the-wire".
> 
> Both drafts decide the maximum application-layer message size based on
> the maximum network-layer packet size (MTU). The problem is that between
> the application layer and the network layer you will have things like
> MIP and IPsec that may increase the size of the message and things like
> SigComp that may reduce it.
> 
> IMO, trying to resolve a problem that only applies to legacy systems
> (any future UA/proxy that handles large messages will implement TCP
> and/or SCTP) by providing only approximate solutions is not a good idea.
> And since any complete solution would be too complex, I would suggest
> that we skip solving this issue. If a legacy system needs to be upgraded
> to be congestion safe, it should implement a simple TCP stack (no TCP
> features are needed) rather than implement UDP tricks.
> 
> I realize that the content indirection mechanism proposed by Hisham
> could be used regardless of the MTU... but that's another story.
> 
> Comments?
> 
> Gonzalo
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