Bogdan-Andrei,

Can you please point me to where in the RFC says this? I suspected this myself, did some reading, and came up with the following from section 8.2.6.2:

"The same tag MUST be used for all responses to that request, both final and provisional (again excepting the 100 (Trying))."

Alistair Cunningham, Integrics Ltd, +44 (0)7870 699 479 http://integrics.com/

Bogdan-Andrei Iancu wrote:

According to RFC 3261, the UAC *must* drop any To-tag received in a provisional reply in favour of the To-tag advertised in the final reply

• be this it means not only to accept a final reply with a different

To-tag, but also to use it in generating sequential messages (like ACK, re-INVITEs, etc)

So you should report the problem to your UAC vendor. Meanwhile you can do a trick in SER cfg - use a reply_route to remove the To-tag from all provisional replies....this will make happy the UAC.

bogdan

Alistair Cunningham wrote:

...

I'm trying to implement forwarding to voicemail with a UAC that's picky about the tags in the To: headers it receives.

First, I tried the following:

failure_route [1] { rewritehostport("192.168.1.1:5060"); append_branch(); t_relay(); }

This failed because the UAC received a "180 Ringing" from the ringing Grandstream phone via ser that contained a To: tag. After the timeout, it received another 180 from Asterisk (the voicemail system) with a different tag. Since it doesn't support forked INVITES, it dropped the call.

Then I tried:

failure_route [1] { rewritehostport("192.168.1.1:5060"); t_reply( "302", "Moved Temporarily" ); }

This time it receives the 180 from the phone as before. Then it receives the 302. Alas, SER has ignored the tag from the phone, and created a new one of it's own, so the UAC again drops the call.

Does anyone know of a way round this? Can SER be persuaded to use a tag it has already received? Can I strip the tag from the To: header in one or both of the responses? I'm willing to get my hands dirty with the SER source code if necessary.