[Serusers] stateless/statefull processing and INVITE method retransmissions

[Michael Kaufmann]

Hi again,

I see that the registrar part of SER is using SL module.
I am trying to build my own authentication - simply use the PRE_SCRIPT_CB 
callback (without using the configuration file) to send some of the data in 
SIP requests to my own server without reparsing the message.
The problem occures when the user is not authorized - when the callback 
return value is 0 no answer is sent back to the client, and I would like to 
send him the not authorized reply.

How can it be done if the only way to hook request answers is using TM?

Another problem - I really didn't understand from the documentation if the 
authentication module is able to do what I described above (my server might 
be in another computer and has to be able to handle more than one SER - It 
might even exchange data with the SIP clients)

Can someone give me an idea of how to implement the SER side module for such 
a server?


Thanks in advance,

Micky


>From: Andrei Pelinescu-Onciul <pelinescu-onciul at fokus.fraunhofer.de>
>To: Michael Kaufmann <mkaufmannn at hotmail.com>
>CC: serusers at lists.iptel.org
>Subject: Re: [Serusers] stateless/statefull processing and INVITE method 
>retransmissions
>Date: Fri, 12 Nov 2004 10:17:06 +0100
>
>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

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