[SIPForum-discussion] Session-expires inclusion in UPDATE

[Paul Kyzivat]

On 11/23/15 11:27 AM, José Antonio Jíménez Rodríguez wrote:
> Hi all
>
> I have a question for you
>
> VoLTE-VoLTE call, preconditions are used (so, A-party will send an UPDATE when preconditions are fullfilled on A-party side)
>
> Should a VoLTE UE add Session-expires on that UPDATE?
>
> 3GPP documents are not clear on that:
> *24.229 does not detail the contents of the UPDATE that A-party should send when preconditions are fullfilled
> *24.930 (Signalling flows for the session setup in the IP Multimedia core network Subsystem (IMS) based on Session Initiation Protocol (SIP) ), does not include Session-Expires on any message but some cases (INVITE when no preconditions are used)
>
> I can see different VoLTE UE behaviour, and when UE does not add it on this precondition-UPDATE, in some implementations, the network adds it...

This is probably addressed to the 3gpp community.

A general answer is that including Session-Expires to UPDATE is 
optional, depending on whether you want to have a session timer.

If a session timer was negotiated via the INVITE, then leaving 
Session-Expires off of the UPDATE will cancel that session timer.

	Thanks,
	Paul