Subject: RE: [Sip] B2BUA & Max-Forwards

From: Phil Reynolds <[email-masked]>
Date: Wed, 4 Dec 2002 09:36:53 -0000

Now your back to restricting what I can and can't do in an intermediary. It
can't be a B2BUA 'cos it doesn't need to honour require headers (the UA at
the other end does that, if they were meant for my intermediary then they
would be proxy-require?), and it can't be a proxy 'cos of the rules about
not changing the body so what is it?

It's not sanctioned by the RFC, yet id does an important and useful job.

-----Original Message-----
From: Adam Roach [mailto:[email-masked]] 
Sent: 04 December 2002 00:37
To: 'Padma Suresh'; [email-masked]; [email-masked]
Cc: [email-masked]
Subject: RE: [Sip] B2BUA & Max-Forwards

-----Original Message-----
From: Padma Suresh [mailto:[email-masked]]
 
> A B2BUA needs to propagate some of the headers received in a 
> request/response to the other endpoint. Example: Require...

No. As emphatically as possible: NO. This is completely wrong, and it
appears to be a growing -- and dangerous -- misconception.

A B2BUA cannot transparently pass Require through. It must understand and
invoke the extension indicated.

  "The Require header field contains a list of option tags, described in
   Section 19.2.  Each option tag defines a SIP extension that MUST be
   understood to process the request."

A back to back user agent *is* a UAS, and *is* bound by this provision.

Whether the UAC portion then turns around and imposes the same requirement
on the UAS it contacts is a local decision.

/a
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---

From: "Cullen Jennings" <[email-masked]>
Date: Wed, 4 Dec 2002 12:04:17 -0800

RE: [Sip] B2BUA & Max-ForwardsI think the answer to what it is is fairly
simple - it's not a proxy and it's not a B2BUA.

And in some call flows, it will probably be called broken :-)

Cullen

  -----Original Message-----
  From: [email-masked] [mailto:[email-masked]]On Behalf Of Phil
Reynolds
  Sent: Wednesday, December 04, 2002 1:37 AM
  To: [email-masked]
  Subject: RE: [Sip] B2BUA & Max-Forwards

  Now your back to restricting what I can and can't do in an intermediary.
It can't be a B2BUA 'cos it doesn't need to honour require headers (the UA
at the other end does that, if they were meant for my intermediary then they
would be proxy-require?), and it can't be a proxy 'cos of the rules about
not changing the body so what is it?

  -----Original Message-----
  From: Adam Roach [mailto:[email-masked]]
  Sent: 04 December 2002 00:37
  To: 'Padma Suresh'; [email-masked]; [email-masked]
  Cc: [email-masked]
  Subject: RE: [Sip] B2BUA & Max-Forwards

  -----Original Message-----

  /a