[Serusers] Tags, forwarding, redirects, and picky UACs

[Bogdan-Andrei Iancu]

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.
>