[VoiceOps] PSTN connection to SONUS

Alex Balashov abalashov at evaristesys.com
Thu Nov 12 12:07:04 EST 2009

"Supports" SS7 is a nebulous notion. SS7 entails a pretty large 
protocol stack and capabilities set.

Asterisk-ss7 supports basic ISUP and it mostly works, so it's a 
potentially functional replacement for PRI in places where telcos 
prefer private SS7 to PRI for access.

Beyond that particular application, it is mostly useless from a 
service provider or carrier standpoint.

It does not support TCAP at all, so no LNP/CNAM/LIDB.

Secondly, it does not support any outboard media gateway control 
protocols - no MGCP or H.248/MEGACO.  So, you can't use an Asterisk 
signaling agent to drive a horizontally scalable farm of independent 
media gateways;  as with everything else, Asterisk integrates the 
signaling and bearer plane into one unitary process and one host.  The 
signaling link must be physically associated with the bearer trunks.

In practice, this means that the inter-machine trunk group size you 
can signal is limited to how many T1s can practically go into a PC 
host running Asterisk;  to me, that's 4, though some people think you 
can put 5-8 T1s into a PC with dual quad-port cards.

It might be good for connecting to a Sonus, but not if you want to 
signal more than a handful of T1s.  I strongly suggest you follow the 
advice to use PRI instead, as it's also much better supported and 

-- Alex

Carlos Alvarez wrote:

> On 11/12/09 7:55 AM, Jason Vanick wrote:
>> Actually you'll probably want to use a PRI config
>> ISUP is used if you're connecting to a switch that requires SS7 
>> signalling.
>> as far as I'm aware, asterisk doesn't support SS7.
> Asterisk does have partial support for SS7.  Last time I looked into it 
> the major functions were there, but not all of them.  However there have 
> been Asterisk servers in production using SS7 for at least a year and a 
> half, possibly more.
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Alex Balashov - Principal
Evariste Systems
Web     : http://www.evaristesys.com/
Tel     : (+1) (678) 954-0670
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