[SIPForum-discussion] SIP signalling during voice mail in IMS domain

[Stephen James]

There could be a number of implementations.  Likely, there would be no ringing as the network would know that the phone was offline. I would expect that the call would be directed to the voice mail system and the SDP of the voice mail system would be delivered in a 183 or it could be a 200 ok. The 200 OK would be used to ensure the INVITE transaction does not expire while collecting the voice mail. A 180 would be unlikely as this implies that the called party is available. Note, if the voice mail system does not support VoLTE codecs a transcoder might be inserted which would be transparent to the caller, other than the IP of the media would not be the voicemail system. 

Sent from my iPad

> On Aug 21, 2014, at 12:40 PM, pendyala syam <psyam545 at gmail.com> wrote:
> 
> Hi All,
> 
> Somebody please explain the sip signalling in the following scenario
> 1. A and B are two VoLTE devices
> 2. B is subscribed for Voice mail service and currently switched off.
> 3. A made call to B. 
> what is the sip signalling here in this scenario??
> 
> My basic doubts are
> a) will call ring??(do we get any 180 Ringing, if so why?)
> b) As far I know, server will to play something like "the customer u are trying to call is
>    currently switched, you can leave voice mail *****".
>    Will this be played after 200OK or before 200OK.
> 
> Thanks...
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