Re: Conceptual doubt between an ASP and SGP

From: Brian F. G. 
> David Laight wrote:                            (Fri, 14 Mar 2014 10:02:43)
> > From: Brian F. G. Bidulock
> > > David,
> > >
> > > David Laight wrote:                    (Fri, 14 Mar 2014 09:46:14)
> > > >
> > > > The return message can also be routed on GT.
> > >
> > > Theoretically, but not in practice.
> >
> > I'll find some customer traces out...
> > I really don't remember seeing one where the source address
> > had 'route on pointcode and ssn' set.
> >
> > I'm pretty sure that most of the TCAP messages we see are
> > routed by GT in both directions.
> > It might be useful to send the response back to system the
> > request came from (ie assuming symmetric routing), but that
> > uses the pointcode from the routing label - N2 in this case.
> 
> GTT does not alter the OPC of the original message.
> 
> Calling Party Address is only used to identify the caller for
> transaction processing and is not used for reverse routing.
> 
> GTT can only exist at an intermediate node in the SS7 network
> that has the transfer function.  That is the definition of
> intermediate node in SS7.

You seem to be confusing the MTP3 STP functionality (which forwards
messages based on the routing label - and doesn't modify the label)
with SCCP forwarding based on GT lookup.
If SCCP forwards a messages (with or without rewriting either GT)
then MTP3 will put the local pointcode in the routing label.

SCCP can forward messages in a node that doesn't have MTP3 STP
functionality. Indeed it can forward the message into an entirely
different SS7 network. It could, for example, forward a message
from an ITU network into an ANSI one (leaving you with ITU TCAP
embedded in ANSI SCCP).

	David