What you have said is already clear from the specification, however, I am not refering to the SDP in 183 being sent as an answer. In the scenario I am dealing with, no SDP is sent in the Invite in the first place, so this is different from what is detailed in the specification.
Cheers,
Steven
Christer Holmberg (JO/LMF) wrote:
Hi,
It is allowed to send an SDP answer an unreliable 18x. The reason it's not considered as a "valid answer" is because it's unreliable, so if it gets lost and a new offer is sent the whole offer/answer state would get out of synch. However, that doesn't mean that you can't use the SDP you receive in un unreliable 18x, und you can assume that the SDP will not change in any additional 18x (or 200) for the same dialog within the same transaction.
Regards,
Christer Holmberg Ericsson Finland
-----Original Message----- From: Steven Egan [mailto:[EMAIL PROTECTED] Sent: 16. helmikuuta 2005 11:35 To: [EMAIL PROTECTED] Cc: Christer Holmberg (JO/LMF); [EMAIL PROTECTED]; [EMAIL PROTECTED]; [email protected] Subject: Re: [Sip-implementors] SDP in 183 non reliable response
Hi Sayan,
I am sending the Invite with no offer to a Cisco AS5350. It is the AS5350 that is sending back the 183 with SDP (I wouldn't refer to it as an offer per se, as it is not a reliable response). I have no control over how the 183 response is constructed, so I was looking to know if it is allowed to contain the SDP or not. I have not found anything in the documentation detailing this. What we are probably going to do is ignore the 183 SDP and wait for the SDP in the subsequent 200.
Cheers,
Steven
[EMAIL PROTECTED] wrote:
Hi,
Bit confused, but how does this help?
As I understand the answer for the offer in the 18x (identical SDP
repeated in the 200), will be answered only in the ACK to
the 200 OK.
So what's the point in doing an "early offer" in an 18x, as
the offer
answer can only be completed when the 200 OK/ACK exchange
takes place.
Does sending an offer in 18x helps in any specific call flow? Just curious...
Regards , Sayan
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf
Of Christer
Holmberg (JO/LMF) Sent: Wednesday, February 16, 2005 4:11 AM To: 'Paul Kyzivat'; Bala Neelakantan Cc: [email protected] Subject: RE: [Sip-implementors] SDP in 183 non reliable response
Hi,
To my understanding the same SDP shall be sent in all subsequent
provisional responses - no matter if they are sent reliably
or not. You
can only have at most one offer/answer exchange per SIP
transaction, so
once you've sent an offer (or answer, if the INVITE did contain an offer) in 18x you can't send any more within that transaction.
When it comes to forking, each dialog is handled completely separate
from each other, ie the offer/answer "state" on one dialog is not
affected by other dialog. How the UAC then chooses which dialogs to
accept/reject, and how to handle possible media received
from multiple
UASs, is an implementation issue.
Regards,
Christer Holmberg Ericsson Finland
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Paul Kyzivat Sent: 15. helmikuuta 2005 18:42 To: Bala Neelakantan Cc: [email protected] Subject: Re: [Sip-implementors] SDP in 183 non reliable response
Bala Neelakantan wrote:
Paul,
I agree that the same SDP should be sent in the subsequent
non-reliable
response and also on the first Reliable response.
I guess you are shifting from the subject of the original question, and discussing a "normal" invite that includes an offer.
What if the call is forked? In that case, there could be multiple provisional responses, each could be potentially different?
How does the
UAC handle those?
This has been well documented and discussed, though it can get complex.
The response to each fork creates a separate dialog. It is up to the UAC to keep the different dialogs straight until one is answered and the others are cancelled.
Paul
Thanks, Neel
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of Paul Kyzivat
Sent: Tuesday, February 15, 2005 9:48 AM To: Steven Egan Cc: [email protected] Subject: Re: [Sip-implementors] SDP in 183 non reliable response
Well, I went back and read to refresh my memory. I agree
that there is
nothing that suggests SDP might be in an unreliable
provisional when
there had been no offer in the initial request.
If it *was* there, you wouldn't be able to consider it a
true offer,
since that must be in a reliable request or response. It
would have to
be a hint of the offer to come. I don't find any language that explicitly *prohibits* this. But in the absence of anything
suggesting
it might be valid you would be best to not count on it.
Paul
Steven Egan wrote:
Hi Paul, So you are saying that when an INVITE is sent with no
offer, a 183 with
SDP can be sent in response? Can you point me to where exactly this is documented please, as my problem is I cannot find anything in RFC 3261 or any other
documentation
to confirm expected behaviour for the 183? Cheers, Steven
Paul Kyzivat wrote:
Steven Egan wrote:
Hi, Is it valid to include the SDP in a non reliable 183 sent
in response
to an Invite with no initial offer?
It is ok to include the SDP in the 183 when the Invite
contains the
initial offer, but RFC 3261 is not clear as to whether
the SDP can be
included when no offer is included in the initial invite.
I believe the answer is YES. The *same* SDP should be sent in the first reliable response.
Paul
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