Call Completion

From Snom Asterisk Portal

Feature description

The CCBS/CCNR supplementary services automatize repeated efforts to reach a currently busy or unreachable subscriber.
CCBS = Completion of Calls to Busy Subscriber;
CCNR = Completion of Calls on No Reply

If the caller invokes the call completion service, the network tries to reach the busy (unreachable) subscriber for a given time in the background. When the call can be finally established (i.e. the subscriber has hung up the active call or becomes reachable), the caller is notified by the network through a ringing of his phone. When the caller picks up the phone, the call will be finally established.

Note! Network side CCBS and CCNR is a dying feature by now, because most VoIP networks do not support it and you will likely never get a callback for a direct dial to a VoIP PBXs extension. This means, that external calls and Call Completion are always depending on the VoIP PBX of the external called party. Below is information about several efforts to implement CCBS/CCNR in Asterisk. Use these methods at your own risk. Another handy method is using the "peer-to-peer call completion" feature on the snom 3xx.

Configure Asterisk

As of Asterisk 1.2.29 and Asterisk 1.4.21, there is no support for CCBS/CCBR in the Asterisk base system.

There are several efforts to implement this feature in Asterisk:

• Focus::VoIP developed an AGI script that handles Asterisk internal call-backs (CCBS and CCNR) via a callback daemon that uses the Asterisk Manager interface to determinate if a subscriber becomes available and to initiate the final callback. It's called "cbapp" and can be downloaded on the Focus::VoIP website. Documentation on how to install and use the script is packaged with the download in the file "README".

Note! When using this script, disable "Peer to Peer Call Completion". Set this option to "off".

• Junghanns.NET is making effort implementing CCBS in their zaptel drivers and the asterisk brifstuff patch. Once Junghanns' work will be completed, one can use the snom phone's CCBS feature out of the box with a bristuffed Asterisk when it's connected to the ISDN network. The ISDN protocol supports CCBS on the network side, so the network will ring back the asterisk when a subscriber becomes available and the bristuffed asterisk will then ring back your phone.