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*-Dev: Announcing chan_ss7, a GPLed SS7 channel driver

Author: Matt Riddell
Daily Asterisk News
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Kristian Nielsen has posted details of a new SS7 driver which works with Digium cards:

Over the last few months, Sifira A/S has been implementing an SS7 channel driver for Asterisk, called chan_ss7. The channel driver works with Digium E1 cards. The licence for the channel driver is GPL.

We are now ready to release the first public version of the code. The purpose of this release is mainly to let people know what we are doing, and to allow other developers with an interest in an Open Source SS7 driver to join forces with us.

I would encourage anyone interested in this, who has the necessary SS7 and Asterisk skills and access to SS7 equipment, to try the code and to send us a note about their interest. The source may be downloaded from Roy Sigurd Karlsbakk has also mirrored here.

To compile it, a recent CVS HEAD version of Asterisk is needed. Success or problems can be reported to

chan-ss7 @

The current state of the code supports voice curcuits on one or more E1 links with a single timeslot 16 signalling link. Incoming and outgoing calls are working. There's a good framework in place for handling the MTP2/3 and ISUP layers. It should be fairly simple to add any missing stuff to this, bit by bit, as the need arises.

Our plan is to extend chan_ulv to support a cluster mode, where two Asterisk boxes running chan_ulv shares a single SS7 point code, with one link on each box making a redundant link set. The two instances of chan_ulv will then do heartbeat monitoring of each other, so that if one box goes down the other can do automatic MTP3 failover and block the dead voice curcuits on the ISUP level, thus eliminating single point of failure for the system. However, none of this cluster mode has been implemented yet.

- Kristian.


Kristian Nielsen kn @
Development Manager, Sifira A/S


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