[Serusers] Session-Expires Header

Nils Ohlmeier lists at ohlmeier.org
Wed Mar 9 14:59:46 CET 2005


On Wednesday 09 March 2005 14:24, Jan Janak wrote:
> On 09-03 11:04, Nils Ohlmeier wrote:
> > I did not wanted to write down this special case, but I feared that
> > someone will come up with it :-)
> > But in this special case you will also have to watch out for the replies,
> > if they contain a Session-Expires header. The draft gives a fairly good
> > overview what a new SER module would have to do ;-) (although it should
> > also be doable in the script itself).
>
>   It can be done in the script, there is no need for a new module, we
>   have been using it with cisco gateways, they do support session timer,
>   so the proxy server inserts the headers into requests and replies.

I think in many cases new modules only add more comfortable "high level" 
functions, which could also be achieved by writing your own script code.

>   You can test for an INVITE coming from cisco and set an onreply_route.
>   In the onreply_route you can do something like:
>
>   if (status =~ "2[0-9][0-9]") {
>   	remove_hf("Session-Expires");
> 	append_hf("Session-Expires: 120;refresher=UAC\r\n");
>   };

But that is actually a vialoation of the Session-Timer draft: the proxy is not 
allowed to change (or add) the refresher in the Session-Expires header. Just 
adding a Session-Expires header to the reply, if it is not present, should be 
sufficient for any implementation which is fully compliant to the latest 
Session-Timer draft.

Greetings
  Nils

>   which "emulates" session-timer support in the user agent that sent 200
>   OK. After receiving such a reply, the cisco gateway would keep sending
>   re-INVITEs.




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