Subject: [Sip] Question on manyfolks 05

From: "Chen, Xin (Xin)" <[email-masked]>
Date: Wed, 6 Mar 2002 10:56:31 -0000

In section 11,

None of the examples shows the PRACK/200 following the INVITE/183 as a new
offer/answer exchange, but I think this is allowed, am I right?

If this is allowed, if the PRACK carries new offer without precondition,
does this mean that the caller doesn't need precondition anymore and the
callee can start ringing whenever it wants? 

If the PRACK carries new offer contain precondition in the SDP (mandary
precondition is present), does this PRACK also needs the
require:precondition header? I think the answer is yes. Am I right?

Thanks

Xin Chen

Lucent Technologies
Tel: +44 1793 883137
Mobile: +44 7799 034668

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From: Gonzalo Camarillo <[email-masked]>
Date: Thu, 07 Mar 2002 01:18:54 +0200

Hello.

> offer/answer exchange, but I think this is allowed, am I right?

The PRACK can carry an anwer. About a PRACK carrying an offer, it should
not be done, because you would not have a way of refusing the offer
without refusing the PRACK itself.

> callee can start ringing whenever it wants?

If at any time you send an offer without preconditions, the callee will
be alerted.

> require:precondition header? I think the answer is yes. Am I right?

Yes.

Gonzalo

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From: Christer Holmberg <[email-masked]>
Date: Thu, 07 Mar 2002 10:03:25 +0200

Hi,

> without refusing the PRACK itself.

Chapter 5 in 100rel says:

"If the UAC receives a reliable provisional response with an answer, it MAY
generate an
additional offer in the PRACK. If the UAS receives a PRACK with an
offer, it MUST place the answer in the 2xx to the PRACK."

"MAY" does not mean the same as "SHOULD NOT". Do we need a change in the text?

However, IF the UAC receives a PRACK, with an offer it does NOT accept, what
about sending a 2xx response to the PRACK, and a 415 response to the INVITE?
Does it really matter if it refers to the session description in the INVITE, or
in the PRACK, since the session setup has failed?

Regards,

Christer Holmberg
Ericsson Finland