Re: M3UA: ASP Route Availability to SG/STP

Howard,

There are three scenarios:  ASP/SG, multiple SG as STP and IPSP.
I think that you are talking of the multiple SG as STP case.

For the multiple SG as STP scenario, the ASP can be viewed as
a separate SEP with its own signalling point code distinct from
that of the STP point codes.  The associations to the SG/STP can
be viewed as a linkset.  The STP signalling point codes can be
viewed as adjacent STP.  In the normal SS7 case where the SEP is
connected by A-links, the STP signalling point codes are treated
as available whenever a signalling link in the directly connecting
link set is available at level 3, or whenever a routeset to the
STP via the alternate STP is available.

When the first association to an SG/STP pair becomes available to
carry traffic (AS-ACTIVE), the ASP is acting in the role of a
restarting MTP at an SEP.  Instead of traffic restart messages,
the M3UA at the ASP can use the DAUD procedure to effect MTP
restart.  When an association to an SG/STP becomes available and
there is an existing association, or the ASP has sufficient recent
knowledge of routing, the ASP is not a restarting MTP however the
DAUD procedure may still be used to establish the availability
of destinations via the SG/STP before starting or restarting
traffic to the SG/STP.  Nevertheless, the ASP may simply restart
traffic to the SG/STP and handle whatever DUNA messages it
receives as a result of restarting traffic instead of using the
DAUD procedures.

As regards the point code of the STP itself: the ASP is acting
as a directly connected SEP (as though it was connecting using
A-links) and therefore, as soon as a link in the linkset (in
M3UA's case, an association) is available at level 3 directly
connected to the STP, the STP's point code is available.  In
SS7, no TFA or TFP is sent to the SEP on a directly connected
A-linkset for the STP's own point code, only for point codes
available via the STP.

So, yes, the ASP acting as an SEP in a multiple SG as STP case
can assume that once it has an association to the SG/STP and is
AS-ACTIVE for traffic via that SG/STP, it can assume that the
SG/STP's point code is available.  However, the point I was
trying to make is that the ASP can simply assume that any point
code is available via an association and route traffic to it,
dealing, of course, with any DUNA that it receives regarding
the traffic it sends.

--brian


Howard May wrote:                            (Tue, 02 Sep 2008 10:59:07)
> Hi Brian, 
> 
> Thanks for your response but I'm still unclear whether when the AS
> becomes active M3UA should immediately consider the route to the SG/STP
> as available or whether it should wait for a DAVA. I'm also unclear
> whether the SG should respond to DAUD concerning the SG/STPs Point Code
> or not.
> 
> Best Regards
> 
> Howard

-- 
Brian F. G. Bidulock
[email protected]
http://www.openss7.org/