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List:       sems
Subject:    Re: [Sems] [SR-Users]  Solutions to missing BYEs,
From:       Stefan Sayer <stefan.sayer () googlemail ! com>
Date:       2010-04-23 18:55:34
Message-ID: 4BD1ED26.3010102 () googlemail ! com
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Hi,

in r1821 you can find my first shot at this scenario, a b2bua which 
enables SST on both sides, and does the SDP ping pong as below.

I am sure that there are many cases which are not handled properly, 
for example, if we have started one INVITE ping-pong from the B2B, 
then we should not accept re-INVITE from the ends, but refuse them 
with 491; atm I think the re-INVITE would just get relayed and two 
INVITE transactions would be running simultaneously.

Another issue is what to do when re-INVITE fails, I think that this is 
not handled properly at the moment (it is just ignored, but should 
probably tear down both calls - that's the thing for, I guess).

A third todo is to pass the headers through. Possibly, this should be 
implemented with a header filter or the like.

Regards
Stefan

Klaus Darilion wrote:
> Yes, it is complex if the B2BUA does not have a media relay ( in which 
> case providing the SDP (at least the port information) itself).
> 
> Am 22.04.2010 16:01, schrieb Stefan Sayer:
>>
> 
>> or, other possibility, empty reinvite:
>> A                  b2b                  B
>> |---INVITE / SDPa-->|                   |
>> |                   |---INVITE / SDPa-->|
>> |                   |                   |
>> |                   |<-- OK/SDPb--------|
>> |                   |--- ACK ---------->|
>> |<-- OK/SDPb--------|                   |
>> |--- ACK ---------->|                   |
>> |                   |                   |
>>          ... sst timer expires ...
>> |                   |                   |
>> |<--INVITE          |                   |
>> |                   |                   |
>> |--- OK/SDPc------->|                   |
>>        now what? ignore that, or do
>>
>> |                   |---INVITE / SDPc-->|
>> |                   |<-- OK/SDPd--------|
> 
> This is the proper approach.
> 
>>          one more ping-pong?
> 
> No.
> 
>   |<----ACK/SDPd------|----ACK----------->|
> 
> No more ping-pongs needed.
> 
> regards
> klaus
> 


-- 
Stefan Sayer
VoIP Services Consulting and Development

Warschauer Str. 24
10243 Berlin

tel:+491621366449
sip:sayer@iptel.org
email/xmpp:stefan.sayer@gmail.com


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