Re: Conceptual doubt between an ASP and SGP

From: Brian F. G. Bidulock 
> David,
> 
> David Laight wrote:                         (Fri, 14 Mar 2014 11:02:08)
> > >
> > > 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).
> 
> 
> Not confused: read Q.714/2.7.5.

Yes, but what has that to do with the colour of sliced bread?
Section 2.7.5.1 is all about ensuring that the original opc
is available when the calling party address is 'route on pc+ssn'.

> But you didn't answer my question: why would you want to mislabel it?

It would be mislabelled if the routing label contained anything other than
the pointcode of the last SCCP node that processed the message.

Indeed the MTP3 should ensure that all messages from userparts contain
the local pointcode (or a known alias pointcode) as the originating pointcode
in the routing label. The only messages it should send with any
other originating pointcode are those forwarded by the MTP3 STP code.

SCCP can relay messages in a system that doesn't have MTP3 STP
functionality.

	David