[Serusers] stateless/statefull processing and INVITE method retransmissions

[Andrei Pelinescu-Onciul]

On Nov 11, 2004 at 16:59, Michael Kaufmann <mkaufmannn at hotmail.com> wrote:
> Hi,
> 
> Ser is pretty new to me (about 3 weeks of reading about it and working with 
> it), so naturally I have some questions:  (attached - the configuration 
> file I use)
> 
> I saw many examples of configuration files were both SL and TM modules are 
> loaded.
> In such cases is SL loaded only for REGISTER requests?

sl is loaded for stateless replies. If you want to send only an error
reply and you haven't called any tm functions (t_newtran, t_rely) and
you are not in a failure route, it's faster to use sl_send_reply (it
doesn't make sense to keep state in this case).

> How can I control which of SER actions are handled with TM and which are 
> handled with SL?

sl handles only stateless replies. If you want to send a request
statelessly use forward(uri:host, uri:port).
If you use t_relay instead of forward than you use tm.

> Is there a way of hooking SER answers to requests without TM?
No.

> 
> As I understand from this mail archive - INVITE is a special case in SER 
> and even though the client doesn't retramit such requests, SER does. Is 
> there a way to avoid this retransmission? Is there a way to control the 
> interval time between one retransmission to another?

In statefull mode (TM), ser retransmits the request on behalf of the
client. THe retransmission stops when a reply is received or after some
timeout. The time between retransmissions is not constant, it increases.
See the sip rfc for more details (rfc3261).
> 
> It seems that sometimes these retransmissions occure even after the ACK is 
> returned...

The INVITE retransmissions stops when a reply to it comes.
ACKs "control" the replies retransmissions. ACKs to INVITE positive
replies are handled a little differently than ACKs to negative replies.
You might have a non-matching ACK, or the ACK might not reach the
desired target. 

> Another starnge this is that my clients are on the same domain as the one 
> SER is on and still record_route() seems to add many non usefull header 
> lines for such INVITE messages.

If you don't need record routing then don't use it.

> 
> Is it a problem with my configuration file?
> 


Andrei