Re: [Sip-implementors] session refresh, but without SDP ?

[Paul Kyzivat]

Troy,

Well said. I fully agree with you, including what A *should* include in 
its offer.

        Paul

Troy Cauble wrote:


From: "Neeraj Jain" <[EMAIL PROTECTED]>

Hi,

As per sec 14.1 of RFC3261, both of these are valid scenarios. This 
says, in
context of re-INVITE SDP, that - "It is important to note that the full
description of the session, not just the change, is sent."

Absence of SDP in re-INVITE means that it's a re-INVITE without an 
offer, in
which case first reliable response to it will contain an offer and usual
offer/answer process will follow.

Regards,

Neeraj Jain
BayPackets Technologies

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Banibrata
Dutta
Sent: Tuesday, August 23, 2005 5:30 PM
To: 'Banibrata Dutta'; Sip-implementors@cs.columbia.edu
Subject: RE: [Sip-implementors] session refresh, but without SDP ?

Additional info:

NOTE: Here the "UAS" is the refresher.

A                B
---INVITE(sdp)---> : M1 <--200 OK--------- : M2
---ACK-----------> : M3
      ...
<--INVITE()------- : M4
case1:
---200 OK(sdp)---> : M5
case2:
---200 OK--------> : M5'

Is the case1 the valid scenario in case of session refresh, i.e. M5 
contains
same "sdp" as M1 ?
or, is the case2 a valid scenarios ?

- bdutta

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Banibrata
Dutta
Sent: Tuesday, August 23, 2005 4:42 PM
To: Sip-implementors@cs.columbia.edu
Subject: [Sip-implementors] session refresh, but without SDP ?

Hi,

Does absence of body (SDP) in the re-INVITE used to do session-refresh 
(in
case of Session-Timers), signify that media properties remain 
unchanged from
the previously negotiated ones, or does it mean, no media, i.e. any
established RTP sessions are to be torn down, if re-INVITE doesn't 
contain
body ?

thanks & regards,
bdutta


Bdutta,

It does not mean "no media".  It means UA "A" should make an
offer in a response.

And while a re-INVITE is a session-refresh, UA "A" can't know
that that's the primary purpose of the re-INVITE.  A re-INVITE
without offer could indicate a 3PCC-like flow where "A" is
about to be connected to another UA.

So should the SDP offered remain unchanged from the previous
negotiation?  That's up to UA "A"; if "B" needs it to be
the same, it should have sent the offer.

In my opinion, "A" should send an offer with all supported
coders, not the possibly reduced set from the previous
negotiation, because it may be opening negotiations with
a new peer.  But that's not a SIP requirement, that's
a policy.

-troy
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