[Devel] New module for OpenSER - Application Server interconnection

[Elias Baixas]

Hello everybody,

I just submitted a new module, called SEAS (which stands for Sip Express 
Application Server).
This module allows a third party to create an Application Server and 
connect it to OpenSER to interoperate seamlessly.
This permits the Application Server to trigger actions on OpenSER, such 
as sending out a request, or replying a UAS transaction, in some way 
similarly to what can be achieved using fifo, or MI commands "t_uac_dlg" 
and "t_reply", but SEAS provides a much richer API to this kind of tasks.
The module also allows OpenSER to notify the Application Server when 
requests/responses come in, and then transfer the control over the 
incoming request entirely to the Application Server.
Furthermore, the module implements a binary protocol that transfers the 
SIP message along with information abouth the structure of the message's 
headers (ie. where each header starts, and how long it is), so the 
Application Server doesn't need to reparse the entire SIP message, thus 
improving Application Server's performance very much.
The SEAS protocol also carries information about the transaction being 
processed at OpenSER for every message, so that the Application Server 
doesn't need to implement all the SIP-transaction machinery, thus 
actually profitting from the highly optimized TM module at OpenSER.

The Application Server can be programmed in any language, because the 
SEAS module comunicates with it through a TCP socket.

At the moment, SEAS module has been written to work with an Application 
Server developed by VozTelecom. It is called WeSIP and can be downloaded 
freely from http://www.wesip.eu . WeSIP is an implementation of the 
SipServlet and HttpServlet standards, so it allows a programmer to 
easily implement Web-Sip converged applications (such as Click2call).
WeSIP is programmed entirely in Java, so you have all the tools and 
facilities from Java and J2EE available to program SIP applications, 
while already using OpenSER to process the SIP messages and transactions 
at the low level, thus profitting both from the high performance of 
OpenSER, and the high-level SIP-Application programming framework which 
is SipServlet and the JAVA languaje.

I hope this module will help create new usage scenarios for OpenSER, 
allowing it to provide high-level Telephony Applications to users.

The module is still in a alpha stage, but should be able for production 
shortly.


best regards,

Elias Baixas

VozTelecom, Sistemas
http://www.wesip.eu
http://www.voztele.com