B2B_SCA module

Admin Guide

Overview

This module provides core SCA (Shared Call Appearance) functionality for OpenSIPS. It is designed to work in tandem with the presence_callinfo module.

The module handles the basic SIP signalling for call controll while publishing callinfo events to a presence server. It is built on top of the b2b_logic module and it is using the ‘top hiding’ scenario to control SIP signalling.

A typical usage example is provided below, where Alice makes a call to Bob. The call leg between Alice and the b2b_sca server is an “appearance” call of the “shared” call between the b2b_sca server and Bob.

   caller         caller      b2b_sca     callee   presence server
alice1@example alice2@example  server   bob@example watcher@example
     |              |             |           |           |
     |--INV bob------------------>|           |           |
     |              |             |--INV bob->|           |
     |              |             |--PUBLISH(alerting)--->|
     |              |             |<-----200 OK-----------|
     |              |             |           |           |
     |              |             |<-180 ring-|           |
     |<-180 ring------------------|           |           |
     |              |             |           |           |
     |              |             |           |           |
     |              |             |<-200 OK---|           |
     |<-200 OK--------------------|--ACK----->|           |
     |--ACK---------------------->|--PUBLISH(active)----->|
     |              |             |<-----200 OK-----------|
     |              |             |           |           |
     |--INV bob (hold)----------->|           |           |
     |              |             |--INV bob->|           |
     |              |             |--PUBLISH(held)------->|
     |              |             |<-----200 OK-----------|
     |              |             |<-200 OK---|           |
     |<--200 OK-------------------|           |           |
     |              |             |           |           |
     |              |--INV------->|           |           |
     |              |             |--INV bob->|           |
     |<-BYE-----------------------|--PUBLISH(active)----->|
     |--200 OK------------------->|<-----200 OK-----------|
     |              |             |<-200 OK---|           |
     |              |<-200 OK-----|           |

Alice calls Bob from her desk IP phone (alice1).
Bob answers the call.
Alice decide to carry the conversation from a meeting room and she put’s BOB on hold.
Alice arrives to the meeting room and retrieves the call on the conference room IP phone (alice2).

To-do

Features to be added in the future:

possibility to handle unlimited number of appearances.

Dependencies

OpenSIPS Modules

The following modules must be loaded before this module:

tm module. pua module. b2b_logic module.

Exported Parameters

hash_size(integer)

The size of the hash table internally used to keep the shared calls. A larger table means faster acces at the expense of memory. The hash size is a power of number two.

The default value is “10”.

...
modparam("b2b_sca", "hash_size", "5")
...

presence_server(string)

The address of the presence server, where the PUBLISH messages should be sent (not compulsory). If not set, the PUBLISH requests will be routed based on watcher’s URI.