Incoming calls through SS7 for data modem transmissions – possible??

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We are working on implementing a solution for a medium service provider.
They were previously using a Cisco AS5300 gateway with some PRI trunks to
receive modem calls, then route them out the Internet.

The Telco they were buying the trunks to discovered this configuration and
restricted them due to legal conventions, and stated that in order to
continue doing this, they would have to talk SS7 directly.

We are planning on solving this by placing an Asterisk server with some
TE410 cards talking SS7 to Telco, and another 4 ISDN ports talking to the
AS5300 for the dial-up to complete after authenticating against a RADIUS

My questions is: can we use only Asterisk to complete/terminate the dial-up
connection, removing the AS5300 out of the picture?

Current topology to be set-up:
Telco –> SS7 –> TE410P-AsteriskServer –> ISDN –> AS5300 –> Internet

Ideal topology:
Telco –> SS7 –> TE410P-AsteriskServer –> Internet

Some posts talk about zapRAS being able to accomplish this, not quite sure

Sounds like possible:

Sounds like not possible:

Thanks in advance,

*José Pablo Méndez

3 thoughts on - Incoming calls through SS7 for data modem transmissions – possible??

  • Thank you Horacio and Cary.

    We will try receiving SS7, routing via SIP, answering on the AS5300, then
    looping back to itself (out PRI, in PRI ports) in order to invoke the modem
    termination. This way we may be able to spare the TDM cards in Asterisk and
    reuse the E1 ports installed in the gateway.

    Best regards,

    *José Pablo Méndez

    2010/11/24 Horacio J. Peña


  • Just out of curiosity, what country are you in?

    I agree with the others in this thread, this seems very bizzare that the
    telco requires you to do SS7 for dialup connections. I would ask them for
    specifics about the “legal” issues with what you are doing – it sounds to me
    like they are just trying to upsell you on a more expensive product.

    I am in Canada and we run exactly the configuration you are currently
    doing… we still have dialup internet customers that dial into AS5300’s via
    PRI’s. Our telco has a PRI product gear specifically for this use… they
    call it ‘ISP-PRI’ I’m not entirely sure what the restriction is on it…. I
    have also just kind of assumed that it is inbound calls only, but I’ve never
    tried making outbound calls on them. I do know they 25-30% cheaper than our
    regular voice PRIs though.

  • Matt,

    We are located on Costa Rica and so far there’s just 1 TELCO running the
    industrym with the CAFTA treatment the carrier had to open for
    interconnection but they get to define the ground rules for the

    They are arguing ISDN is and “end customer” circuit and you cannot use it to
    “resell” service. You need an “Interconnect” circuit, to resell dial up
    access, and they require you to support SS7 for “Interconnect” T1s

    It’s just the carrier raising the bar waiting for 90% of the competition to
    drop off, and a little porcentage to make it.

    We asked for quotes for multiple solutions, most of them ranging 15 000$,
    and finally come to the conclusion Asterisk and SS7 would be the only viable
    option for this project.