Subject: SIP question on retransmition of 2xx response

From: Vipul Patel <[email-masked]>
Date: Wed, 07 Jul 1999 17:59:36 -0400

Let's look at following example:

Client A sends an INVITE request to Client B which goes through stateful
proxy P. Client B sends 200 OK response with a Contact header, which
goes to Client A through proxy P. Now Client A sends the ACK directly to
Client B at the URL listed in the Contact header field. Since the ACK
did not go through the proxy P, it retransmits the 200 OK response, and
eventually timeout. Meanwhile Client A will continue to retransmit ACK
as it receives 200 OK response from proxy P.

Does it make sense for proxy P to retransmit 2xx response in this case
or in general?

Vipul.

--

Vipul J. Patel
dynamicsoft
200 Executive Drive
West Orange, NJ 07052
mailto:[email-masked]

Office:         + 1 732.741.7244
FAX:            + 1 732.741.4778
www:            http://www.dynamicsoft.com

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From: Sean Olson <[email-masked]>
Date: Wed, 7 Jul 1999 19:29:08 -0500 (CDT)

> Does it make sense for proxy P to retransmit 2xx response in this case

No it doesn't. Client B will continue to retransmit its 200 OK response until it
receives an ACK. This re-transmission will go through the proxy P. In effect,
the reliable delivery of the 200 OK response is up to the client (UAS).
This makes P's life much easier :) 

> Vipul.

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Sean Olson            E-mail: [email-masked]
Ericsson Inc.         Voice: (972) 583-5472 
                      FAX: (972) 669-0154