Re: M3UA: ASP Route Availability to SG/STP

Hi Lincoln,

I'm concerned about the availability of the Route to the STP not routes
via the STP. If the STP has point code 'Alpha' then the ASP may have a
route to point code 'Alpha'. It is the availability of this route at the
ASP I am concerned with.

It is clear that routes via the SG/STP will only become active after
receiving DAVA.

Best Regards

> -----Original Message-----
> From: Haresign Lincoln [mailto:[email protected]]
> Sent: 03 September 2008 13:20
> To: Howard May; [email protected]
> Cc: [email protected]
> Subject: RE: [Sigtran] M3UA: ASP Route Availability to SG/STP
> 
> Howard,
> 
> It would seem to me that if the SG responds to an ASP Active message,
> that in effect tells the ASP that the SG is available to begin
receiving
> traffic.
> 
> It's not clear to me.  Are you concerned about the ability of the SG
to
> begin processing traffic.  Or are you concerned about the
> availability/status of all the point codes on the other side of the
SG?
> 
> 
> Regards,
> Lincoln
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Howard May
> Sent: Wednesday, September 03, 2008 6:01 AM
> To: [email protected]
> Cc: [email protected]
> Subject: Re: [Sigtran] M3UA: ASP Route Availability to SG/STP
> 
> Hi,
> 
> I want to ask Sigtran list members / authors opinions about an area of
> perceived ambiguity in the M3UA spec.
> 
> Brian, at present the reasoning behind your expected ASP behaviour is
> based on the MTP3 specs rather than the M3UA specs and an assertion
that
> M3UA should behave the same. The MTP3 specs clearly identify routes to
> adjacent signalling points become available when the direct link set
> comes into service at layer 3 (or after restart completes) and the
Route
> Set Test procedures are not used across the direct link set for the
> adjacent signalling point. But the M3UA spec does not define similar
> behaviour. M3UA does not seem to discuss any mechanism for route
> availability other than reception of DAVA messages.
> 
> While I recognise there may be ambiguity, I feel that at present the
> specification suggests the adjacent signalling point at the SG/STP
> should generate DAVA/DUNA messages and respond to DAUD messages and
> should not be presumed to be available following AS Activation.
> 
> I am concerned about this perceived ambiguity on account of the
> interoperability impact and would value a clear consensus and
> clarification as to the expected behaviour.
> 
> Best Regards
> 
> Howard
> 
> **********
> 
> Concerning M3UA acting in the role of a restarting MTP. MTP Restart
> procedures aim to allow sufficient bandwidth and route synchronisation
> prior to the commencement of traffic. They also aim to reduce the time
> for restart procedures to complete to allow traffic restart as quickly
> as possible. They do this by prohibiting the transfer of traffic in
> either direction prior to exchange of TRA messages and by presuming
> route availability and exchanging only TFP messages.
> 
> M3UA does not support such mechanisms and so will have to handle
traffic
> prior to having a fully synchronised routing table risking possible
> message loss.
> 
> **********
> 
> 
> 
> > -----Original Message-----
> > From: Brian F. G. Bidulock [mailto:[email protected]]
> > Sent: 02 September 2008 17:03
> > To: Howard May
> > Cc: [email protected]
> > Subject: Re: [Sigtran] 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/
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