[SR-Users] early media: How to change to tag

Daniel-Constantin Mierla miconda at gmail.com
Thu Mar 29 09:32:21 CEST 2012


Hello,

On 3/29/12 1:14 AM, Andreas Granig wrote:
> Hi,
>
> On 03/28/2012 06:37 PM, Iñaki Baz Castillo wrote:
>> 2012/3/28 Min Wang<ser.basis at gmail.com>:
>>> In order to properly proxy the msg to GW1, Kamailio seems need to change the
>>> to tag from B to A.
>> Totally wrong. Multiple (early-)dialogs are 100% valid according to
>> RFC 3261. If you find some SIP device failing when it receives
>> multiple 180/183/200 responses with different To-tag, then drop it
> I recently learned that for example Siemens switches implement "Request
> Disposition: no-fork" defined in http://www.ietf.org/rfc/rfc3841.txt,
> and if for some reason you decide to fork nonetheless on your side,
> you'd probably want to do something about the different to-tags
> (although you're violating against that specific RFC then). No idea how
> such a device would react to not getting a to-tag at all by stripping it
> out as Klaus suggested in another response, but at least that Siemens
> switch doesn't bail out on getting different to-tags in provisional replies.
I fully agree that devices not supporting multiple to-tags in 
provisional replies should be dropped, it will make life easier for 
everyone.

Regarding hacks to make an workaround, in many cases I saw devices 
requiring to-tag in 183. In that case, a solution can be dropping 183 
from reply route and send 180 instead with t_reply(...).

Cheers,
Daniel

-- 
Daniel-Constantin Mierla
Kamailio Advanced Training, April 23-26, 2012, Berlin, Germany
http://www.asipto.com/index.php/kamailio-advanced-training/




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