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 Wangser.basis@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