[Serusers] Session-Expires Header

[Zeus Ng]

Yes, you do need UA supporting this header.

According to section 8 of the draft, draft-ietf-sip-session-timer-14:
   Session timers are mostly of interest to call stateful proxy servers
   (that is, servers that maintain the state of calls and dialogs
   established through them). However, a stateful proxy server (that is,
   a server which is aware of transaction state, but does not retain
   call or dialog state) MAY also follow the rules described here.
   Stateless proxies MUST NOT attempt to request session timers. Proxies
   that ask for session timers SHOULD record-route, since they won't
   receive refreshes if they don't.

Here, SER is not a call stateful proxy but transaction stateful proxy. It
will not maintain the state of the call. So, even if you insert the header,
it will not change anything from SER's perspective.

However, if as least one of the UA support this header, you may see a BYE
request, which is good for accounting. If neither UA support the header, no
re-INVITE or UPDATE will be generated and that doesn't help you more than
what you have at the moment.

So, until SER becomes call stateful (which is similar to B2BUA, but not the
same), your best hope will be UA that support this header.

Zeus

> -----Original Message-----
> From: serusers-bounces at lists.iptel.org 
> [mailto:serusers-bounces at lists.iptel.org] On Behalf Of Nils Ohlmeier
> Sent: Wednesday, 9 March 2005 9:04 AM
> To: Java Rockx
> Cc: serusers at lists.iptel.org
> Subject: Re: [Serusers] Session-Expires Header
> 
> 
> On Tuesday 08 March 2005 22:54, Java Rockx wrote:
> > Pardon me for asking such simple questions, but is the answer for 
> > generating re-INIVITE messages to simply use SIP clients 
> that support 
> > the header in its configuration?
> 
> Both UA's have to support the Session-Timer draft, otherwise 
> the inserted 
> Session-Expires Header will simply be ignored and you will 
> never see any 
> re-INVITE's. But if both UA's support the Session-Timer they 
> should normaly 
> agree on using automatically by looking at the Supported 
> header. So in my 
> opinion there is no extra value in adding a Session-Expires 
> header to a 
> request at a proxy.
> 
>   Nils
> 
> > Regards,
> > Paul
> >
> > On Tue, 8 Mar 2005 22:20:06 +0100, Nils Ohlmeier 
> <lists at ohlmeier.org> 
> > wrote:
> > > On Tuesday 08 March 2005 00:52, Java Rockx wrote:
> > > > If I include a session-expires header using 
> append_hf(), do I have 
> > > > to do anything else to my ser.cfg script?
> > > >
> > > > Also, will this cause re-INVITEs to happen or is there 
> something 
> > > > else needed?
> > >
> > > UA's which support Session-Timer?!
> > >
> > >  Nils
> 
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