New subject: [Serusers] stateless/statefull processing and INVITE method retransmissions

14 Nov 2004

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
&lt;pelinescu-onciul(a)fokus.fraunhofer.de&gt;
To: Michael Kaufmann &lt;mkaufmannn(a)hotmail.com&gt;
CC: serusers(a)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 &lt;mkaufmannn(a)hotmail.com&gt; 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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Re: [Serusers] stateless/statefull processing and INVITE method retransmissions