[asterisk-ss7] Incoming calls through SS7 for data modemtransmissions - possible??

Cary Fitch sage at usawide.net
Fri Nov 26 13:44:07 CST 2010

SS7 is “simply” another data channel.  As a 56k or 64K channel, it is not a
great deal different, as far as stress goes, than a D channel on a PRI.
(Only discussing stress on the system.) You do have to have two SS7 channels
per the SS7 standards, for reliability.  From there on, there should be
little to no difference how many 64K channels of audio/modem-tones you can
handle. IMO.


Cary Fitch



From: asterisk-ss7-bounces at lists.digium.com
[mailto:asterisk-ss7-bounces at lists.digium.com] On Behalf Of Marcelo Pacheco
Sent: Friday, November 26, 2010 12:24 PM
To: asterisk-ss7 at lists.digium.com
Subject: Re: [asterisk-ss7] Incoming calls through SS7 for data
modemtransmissions - possible??


I had a quad E1 PCI setup with a PRI to the PSTN and a PRI to an AS5300, the
AS5300 was exactly handling analog modem calls.
Works ok, as long as the CPU is always lightly loaded.
Changing one E1 from PRI to SS7 should make no diference whatsoever if
you're using libss7, since libpri uses DAHDI and chan_dahdi for bridging the
It was like 6 years ago, so I don't even have the scripts. Just saying it
should work, specially with faster (newer) CPUs.

José Pablo Méndez Soto wrote: 

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 <horape at compendium.com.ar>


ZapRAS seems to work only with ISDN calls. "This command is not for use with
analog lines; it does not provide a modem emulator."

You need something doing the modulation. It seems that iaxmodem is your best
bet, and you'll have to make a good bunch of work on it to be able to use as
want to.

If your client has the cisco gateways, I'd suggest you to keep them. They
very reliable and tested, and with MICA cards they have not a high resale
so you'll probably end with them as paperweights unless you happen to have
stack of C549 cards to repurpose them.


On Wed, Nov 24, 2010 at 07:58:37PM -0600, José Pablo Méndez Soto wrote:
>    Hello,
>    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 from, 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 server.
>    My questions is: can we use only Asterisk to complete/terminate the
>    dial-up connection, removing the AS5300 out of the picture? We would
>    probably need a PPP channel configuration to link the modem connection
>    with the Internet.
>    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 though
>    Sounds like possible:

>    [1]http://lists.digium.com/pipermail/asterisk-users/2004-January/026956
>    .html
>    [2]http://lists.digium.com/pipermail/asterisk-users/2009-November/24021

>    8.html
>    Sounds like not possible:

>    [3]http://lists.digium.com/pipermail/asterisk-users/2009-November/24020

>    2.html
>    Thanks in advance,
>    José Pablo Méndez

> References
>    1. mailto:asterisk-users at lists.digium.com
>    2.
>    3.

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Horacio J. Peña
horape at compendium.com.ar
horape at uninet.edu



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