Subject: RE: [Sip] The Problem with PRACK

From: "Samir Srivastava" <[email-masked]>
Date: Thu, 9 Mar 2006 23:33:30 -0600

The proxy doesn't necessarily have much choice in the matter. Possibly 
the UAS is only accessible via UDP.

	Paul

3261 mandated UA to support TCP, quoting from section 18 page 142
"
   All SIP elements MUST implement UDP and TCP.  SIP elements MAY
   implement other protocols.

      Making TCP mandatory for the UA is a substantial change from RFC
      2543.  It has arisen out of the need to handle larger messages,
      which MUST use TCP, as discussed below.  Thus, even if an element
      never sends large messages, it may receive one and needs to be
      able to handle them. 
"
It has been around 4 years. UA MUST have TCP. We need to draw a line
worrying about backward compatibility with 2543. UA is not 3261
compliant and should be fixed. If still it has only
UDP, they will be few and we get gain for optimizing most of the UA
supporting TCP.

Thx
Samir

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_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip

---

From: Aki Niemi <[email-masked]>
Date: Fri, 10 Mar 2006 10:26:18 +0200

> UDP, they will be few and we get gain for optimizing most of the UA

Implementing and using are two completely different things. Even if the
proxy wanted to use TCP for the last hop towards the UA, it won't be
able to connect to a host behind a NAT. This is what sip-outbound is
trying to fix.

Cheers,
Aki