[Asterisk-Dev] About OpenSS7 integration to Asterisk

[Storer, Darren]

Hi,

>It looks like from OpenSS7's website that the T400P (which looks like its
>the same one that digium sells) is a supported device:
><http://www.openss7.org>

Implementing SS7 via "dumb" cards has special diifculties, it's not quite as
straight forward as implementing ISDN PRI.

MTP1 and MTP2 are usually handled by embedded processors on SS7 line card
interfaces; the reason for this is because of the high processing load and
the exacting requirements for timing. The processor load gets worse as the
signalling links become quieter due to the requirement to generate fill-in
signalling units (FISUs).

Here's a quote from Brian F.G. Bidulock on the matter:

BFGB> "Asterisk soft-HDLC code could not handle SS7 (FISUs and
BFGB> LSSUs), was putting too many flags between frames, was
BFGB> discarding frames, wrapping on the receive buffers, ...
BFGB> It would not be possible to meet 10E-6 BER because the
BFGB> Asterisk soft-HDLC was introducing more errors than that
BFGB> leaving nothing for the transmission facility.  Skips and
BFGB> drops and pops might be ok for voice and even line-side
BFGB> ISDN signalling, but is unacceptable for trunk-side
BFGB> transmission and signalling."

It would be wonderful to see cost effective SS7 (especially INAP) solutions
but the requirements for timing usually mean that more expensive
"intelligent" line cards must be used, not to mention the cost of SS7
validation, conformance and performance testing. Without the higher level
SS7 protocol certification it will be very difficult to find a Telco that
will let you connect directly to their switches...

Having said all of this there are some clever people out there and perhaps
the low level real-time stuff can be cracked using an innovative technique.
The greater challenge seems to be convincing Brian F.G. Bidulock that
supporting the integration of OpenSS7 with Asterisk is a positive move, he
doesn't seem have any interest in this exciting possibility! (See quote
below:)

BFGB> "It is clear that Asterisk lacks SS7, but why do you think
BFGB> that OpenSS7 needs Asterisk?"


Regards

Darren
--
Comgate
Telco>Internet<Broadcast

-----Original Message-----
From: asterisk-dev-admin at lists.digium.com
[mailto:asterisk-dev-admin at lists.digium.com]On Behalf Of John Todd
Sent: 07 May 2004 08:14
To: asterisk-dev at lists.digium.com
Subject: Re: [Asterisk-Dev] About OpenSS7 integration to Asterisk


At 9:44 AM +0300 on 5/7/04, Csaba Pócsai wrote:
>Hi,
>
>I found a conversation about OpenSS7 integration to Asterisk on this list's
>archive. See below.
>Is there anyone who knows about that? Is there existing integration
already?
>Is there anyone who dealed with it?
>
>Thank you in advice
>Csaba
>[Asterisk-Dev] OpenSS7
>Nathan asterisk-dev at lists.digium.com
><mailto:asterisk-dev%40lists.digium.com>
>Fri, 14 Mar 2003 19:33:08 +0000 (UTC)
>[snip]
>Hi,
>
>I was wondering if someone is interested, or is currently working on
>integrating OpenSS7 with Asterisk?
>
>
>SS7 is a protocol stack that, with a proper application level program can
>allow for call setup, management and tear down, LNP, 800 and 900 services,
>[snip]
>The source code from the openss7.org site is licensed under the the GPL
>and LGPL.
>
>Thanks,
>Nathan


I will pass along rumor and unsubstantiated
gossip that I don't even remember where I
heard... There were comments that there was too
much bit slipping in the T400P card to pass
"certification" (whoever "certifies" such things)
and that the project lost a lot of steam due to
reliability problems with using the PC interrupt
stream due for whatever sensitive portions of the
project relied on it.  I have no idea if that's
true or not, but this question comes up a lot and
nobody seems to have an answer other than vague
rumors of "over that horizon over there..."

Yes, the T400P is Digium's card.

JT



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