Hi John,
Routing contexts and keys were discussed at length on the IETF's SIGTRAN
mailing list, when M3UA was developed. You can look at the benefits of
this approach in the mailing list archives.
Anyway, would it not be possible for you to provide a M3UA
implementation for Asterisk (even if it is in binary format to protect
your proprietary code)? This would have the advantage of not requiring
us to maintain an additional Diastar server (a potential point of
failure). With the Diastar server, I would also need to purchase more
Diastar servers as my capacity/redundancy requirements increase (in
addition to increasing the asterisk capacity in the backend).
M3UA would provide the benefit of multiple distributed asterisk boxes
that can be added or removed on the fly from their connectivity to the
signalling gateway. With M3UA we would also get the of from using SCTP
in the distributed architecture, with its support for multi-homing,
multiple streams, etc. features.
With Diastar we use SIGTRAN over SCTP towards the PSTN. Do we not loose
all the SCTP benefits by now using TCP from Diastar to Asterisk? As an
example, SCTP reduces head-of-line blocking while using TCP from Diastar
to Asterisk reintroduces head-on-line blocking.
Best Regards,
Amish
On 02/08/2010 09:55 PM, John Hermanski wrote:
Hi Amish,
The main advantage of the client/server relation ship between the
DiaStar server and the Asterisk client is to be able to provide a
distributed system where it is possible to separate the signaling and
network connections (DiaStar) from the application services.
(Asterisk) This is an advantage for larger systems. Multiple
standard, easily built Asterisk boxes can added or removed on the fly
without any adjustments to DiaStar. There's a clean separation
between the application and network connectivity.
While, as you point out, it may be possible to be more efficient by
moving M3UA to the Asterisk systems, our base SS7 products (Dialogic
Distributed Signaling Interface or DSI) do not allow this. The
various SS7 components that make up SIGTRAN/ISUP operate as separate
processes communicating by means of Unix message queues. They are
controlled by a master process that reads the SS7 configuration and
then starts up the needed stacks on the single system. DiaStar uses
DSI, so we have to live within its constraints.
So, rather than dividing work load based on routing contexts or keys,
call distribution to multiple Asterisk systems is done by means of a
"who's least busy and replies first" to the server's request for
someone to handle an inbound call. A "Hello" message is sent from
DiaStar, via Woomera, (the protocol used between Asterisk and DiaStar)
to all Asterisk systems that have registered with the server. The
Asterisk system who replies first (presumably the least busy system)
will be granted the call. We think this is a reasonable way of call
distribution.
John Hermanski
Technical Marketing Engineer
Dialogic Inc.
5 Monroe St.
Salem, MA
USA
Tel: 978 744 9098
Cell: 978 836 8028
Email: john.herman...@dialogic.com <mailto:john.herman...@dialogic.com>
Web: www.dialogic.com <http://www.dialogic.com/>
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