Be careful because the behaviour in the described scenario is only
allowed if all the SDPs are the same.
o If the initial offer is in an INVITE, the answer MUST be in a
reliable non-failure message from UAS back to UAC which is
correlated to that INVITE. For this specification, that is
only the final 2xx response to that INVITE. That same exact
answer MAY also be placed in any provisional responses sent
prior to the answer. The UAC MUST treat the first session
description it receives as the answer, and MUST ignore any
session descriptions in subsequent responses to the initial
INVITE.
With the use of PRACK, the first reliable response becomes the
first response that requires PRACK.
Once you start using PRACK to an SDP answer, the "200 OK" should not
have
an SDP - if the "200 OK" does have an SDP, it should be ignored.
Offer/Answer and PRACK (and UPDATE) are discussed in:
http://tools.ietf.org/html/draft-ietf-sipping-sip-offeranswer-13
Regards,
Attila
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Vivek Batra
Sent: 11 October 2010 05:43
To: 'Ayyanar P K'; '$...@r\/|>r!`/@'; 'Vijay S Nair'
Cc: [email protected]
Subject: Re: [Sip-implementors] UAS behavior : Multiple 18x messages
Hi,
I have found it with several service providers which play announcement
(and hence send 183 Session Progress) to wait if actual called party is
busy and send 180 Ringing as soon as called party becomes available.
Best Regards,
Vivek Batra
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Ayyanar P K
Sent: Monday, October 11, 2010 9:39 AM
To: $...@r\/|>r!`/@; Vijay S Nair
Cc: [email protected]
Subject: Re: [Sip-implementors] UAS behavior : Multiple 18x messages
Hi,
Is there a call flow like this ?
------- INVITE (OFFER)------->
<------ 100 TRYING -----------
<------ 183 PROGESS(ANSWER)---
<------ 180 RINGING(ANSWER)---
<------ 200 OK (ANSWER) ------
------- ACK ----------------->
If so, in which scenario can we find a call flow like the above
mentioned.
Thanks and Regards ,
Ayyanar
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
$...@r\/|>r!`/@
Sent: Monday, October 11, 2010 9:10 AM
To: Vijay S Nair
Cc: [email protected]
Subject: Re: [Sip-implementors] UAS behavior : Multiple 18x messages
1. Can UAS responds with multiple 18x for the INVITE request received?
YES.
2. What should be the behavior of UA1 if it receives multiple 18x?
Create dialog if the response contains tag. Update your state machine.
3. What should be the behavior of UA1 while receiving the second 18x
with SDP?
When the second 18x is rcvd with SDP, you should save the 18x as you
need it to send it back with your ACK. The UAS cannot send diff SDP in
the 2xx now.
Also is there any particular reason that you are sending Invite WO
offer?
On Sat, Oct 9, 2010 at 8:52 PM, Vijay S Nair
<[email protected]>wrote:
> Hi All,
>
> Here is the scenario,
>
> UA1
UA2
>
> ----------------------------------INVITE w/o offer----------------->
> <----------------------------------100
Try------------------------------
>
> Connection / Port Not allocated
> <----------------------------------18x w/o offer
----------------------
>
> Connection / Port allocated <----------------------------------18x
> OFFER -----------------------
>
> Here are my queries,
>
> 1. Can UAS responds with multiple 18x for the INVITE request received?
> 2. What should be the behavior of UA1 if it receives multiple 18x?
> 3. What should be the behavior of UA1 while receiving the second 18x
> with SDP?
>
> Please comment ...
>
> --
> Thanks & Regards
> Vijay Sukumaran Nair.
> _______________________________________________
> Sip-implementors mailing list
> [email protected]
> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>
--
cheers!!!!
sarvpriya
http://sarvpriyak.blogspot.com/
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