[asterisk-ss7] My experiences with chan_ss7, some questions and a solution for the ringback tone

Kai Militzer km at westend.com
Thu Mar 16 02:46:52 MST 2006

Hello Jacob, hello all,

Jacob Tinning wrote:

> We didn't like the timer-solution because we think its wrong to delay all calls
> X seconds just because the SS7-asterisk doesn't know another Asterisk's dialplan.

Thats why I made it configurable, so that it can be turned off, when not 
needed. ;)

> My suggestions is
>  1. Use identical dialplans on the SS7-gateway and the SIP server
>  2. Store the dialplan in a shared database.
>  3. I think it is (maybe) posible to 'share' the dialplan through IAX (anybody ?)

Your suggestions are reasonable if you know the dialplan. In my case it 
can be possible that I will forward a number block to a customer. I have 
not (and will not have) any knowledge of the length of the numbers the 
customer uses, I only know the base of the block, neither does the 
customer have to use an asterisk as termination.

I have a block +49-241-9909888 [0-99999]. I forward this block to a 
customer. This customer can add one to five digits to this block 
depending on his needs and I will never have knowledge of how many 
digits he uses.

As you see, if you want use chan_ss7 as a multi-customer SS7-to-SIP 
gateway with a national numbering plan without fixed length numbers (as 
in the US) there is no way around a timer. It's sad but true. ;)

>>And last but not least, I also had the problem that no ringback tones
>>were generated by asterisk. The following two lines in the dialplan
>>inserted before the Dial statement do the trick:
>>exten => _X.,n,SetLanguage(de)
>>exten => _X.,n,Playtones(ring)
> We actually tried this, but we had to insert a ,1,Answer before the Playtones command.
> ...but the Answer before Playtones, breaks most telcos billing system,
> since a call is 'from the Answer to a hangup'.

It works here without the answer as there is early-Media after receiving 
an IAM. This works also with MOH instead of the ringback beeps, what can 
be quite funny.

Best regards,

Kai Militzer                 WESTEND GmbH  |  Internet-Business-Provider
Technik                      CISCO Systems Partner - Authorized Reseller
                              Lütticher Straße 10      Tel 0241/701333-14
km at westend.com               D-52064 Aachen              Fax 0241/911879

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