[Asterisk-ss7] Re: Let us design an open source SS7 interface for Asterisk

Matthew Crocker matthew at crocker.com
Fri May 13 09:19:14 CDT 2005


  I think it would be much easier, and better to use dedicated  
hardware to terminate the A-link, MTP1 & 2 and pass everything to  
Asterisk via IP.   Something like chan_sigtran.   The standards for  
SS7 over IP are a moving target but it is IMHO where Asterisk should  
be headed.   Traditional SS7 (packet over 56k DS0) is a dinosaur and  
will be replaced over time.  I like the design behind the ss7box.com.  
Companies like Verisign are already doing SIP-7 and SS7 over IP. If  
Asterisk could connect directly to their service a provider wouldn't  
need an SS7 Gateway.  If Asterisk is designed to use a separate  
hardware box for MTP1 & 2 it would allow a lot of flexibility.   The  
SS7 gateway could be another Asterisk box which is purpose built to  
handle the SS7 and hand it off to a call processing (softswitch)  
Asterisk server.

Something like [ss7] -> Asterisk --- [sigtran/mgcp] ---> Asterisk.

  In my perfect world I would have something like:

  SS7 --- [2 x A link ] --->  [SS7 Gateway] ---- [IP]  ----> Asterisk

  PSTN --- [IMT] ----> [Media Gateway] --- [ IP ] ----> Asterisk

   [ IP ] ---> [Media Gateway] --- [PRI] --> [Customer PBX]
   [ IP ] ---> Customer SIP Phone

For Media Gateway I would use Cisco 5350s colo'ed into the Verizon  
COs.  Each 5350 would terminate IMTs from the local Verizon End  
Offices.  Ideally, each 5350 cluster would have their own SS7 point- 
code and be classified as an End Office.  Verizon would be  
responsible for getting their calls to me at my EO.  If they don't   
terminate at the EO they can hand it off to my 'tandem' which is just  
another 5350 plugged into the Access Tandem.    I would use Cisco  
AS5350s because one of my requirements is dialup ISP RAS service.   
Any other media gateway that can handle v.92 (PPP) and g.711/g.729  
could be a replacement for the  5350s

On top of all this the SS7, ISUP, TCAP has to be certified and pass  
testing with Verizon to make any sense.

My requirements might be different, I'm a facilities based DLEC.

I already have dark fiber/GigE and SCOPE colo bays in the Verizon COs  
I'm interested in.  I have IPDLCs that can terminate POTS from  
customers into VoIP (SIP/MGCP).  I have 4.6mbps 2xSHDSL loops to  
customers where I can hang a media gateway (CAC Adit ??) for derived  
PRI delivery.

I have everything but a switch, and I'm pouring over quotes now  
trying to figure out a switch budget


On May 13, 2005, at 8:58 AM, Angel Diaz wrote:

> Lets do this:
> 1-    Is it possible to develope on GLP ?
> 2-    In case the answer is "NO"; What can we do then?
> 3-    In case the answer is "YES"; We have to decide:
>             - Create the SS7 stack as a module in the asterisk ?
>             - Create as an external library ?
>             - etc, etc.
> What user part of the SS7 the people need; ISUP,  TCAP, TUP, etc?
> If we take statistics, about what the people ask for ... it is  
> ISUP, because
> they need to interconect to the PSTN, Cellular Network or other ...
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> Asterisk-SS7 mailing list
> Asterisk-SS7 at lists.digium.com
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Matthew S. Crocker
Vice President
Crocker Communications, Inc.
Internet Division
PO BOX 710
Greenfield, MA 01302-0710

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