[asterisk-ss7] How Asterisk + sigtran ?

John Hermanski John.Hermanski at dialogic.com
Mon Feb 8 13:55:46 CST 2010

Hi Amish,

The main advantage of the client/server relation ship between the DiaStar server and the Asterisk client is to be able to provide a distributed system where it is possible to separate the signaling and network connections (DiaStar) from the application services.  (Asterisk)   This is an advantage for larger systems.  Multiple standard, easily built Asterisk boxes can added or removed on the fly without any adjustments to DiaStar.  There's a clean separation between the application and network connectivity.

While, as you point out, it may be possible to be more efficient by moving M3UA to the Asterisk systems, our base SS7 products (Dialogic Distributed Signaling Interface or DSI) do not allow this.  The various SS7 components that make up SIGTRAN/ISUP operate as separate processes communicating by means of Unix message queues. They are controlled by a master process that reads the SS7 configuration and then starts up the needed stacks on the single system.  DiaStar uses DSI, so we have to live within its constraints.

So, rather than dividing work load based on routing contexts or keys, call distribution to multiple Asterisk systems is done by means of a "who's least busy and replies first" to the server's request for someone to handle an inbound call.  A "Hello" message is sent from DiaStar, via Woomera, (the protocol used between Asterisk and DiaStar)  to all Asterisk systems that have registered with the server.  The Asterisk system who replies first (presumably the least busy system) will be granted the call.  We think this is a reasonable way of call distribution.

John Hermanski
Technical Marketing Engineer

Dialogic Inc.
5 Monroe St.
Salem, MA

Tel:       978 744 9098
Cell:      978 836 8028
Email:   john.hermanski at dialogic.com<mailto:john.hermanski at dialogic.com>
Web:    www.dialogic.com<http://www.dialogic.com/>

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