Re: Upper boundary of Adaptation Layers

Ilie,

Ilie Glib wrote:                                                      (Tue, 10 Jan 2006 15:49:31)
> Brian,
> 
> I am happy about your statements
> 
> > > [Ilie] Therefore an implementation of SUA Layer in may not have any
> > > other primitives than SCCP/SCCP-User primitives. Is this correct?
> > >
> >
> >  Read on:
> >
> > > >It does not say that nothing else is supported or
> > > > supportable.  It does not say that no other primitives shall be used.
> > > > It is just the list of intentionally supported primitives.
> >
> > I don't know what you mean by "rely on."
> 
> [Ilie] My understanding is that SCCP-users are standardized as
> application layers using services provided by SCCP in its primitives
> to the SCCP-Users. Thus applications rely (read use) SCCP upper
> boundary as of Q.711.
> 
> >All SS7 stacks are vendor
> > specific.  The only thing an application can rely upon is the interface
> > provided by the vendor.
> >
> [Ilie] I believe it is not very difficult for SCCP User applications
> to change from SCCP layer of one vendor to another (or from SCCP use
> to SUA), they anyway follow the primitives of Q.711.

It was our objective when formulating the specifications to permit an
implementation that follows the primitives of Q.711 and the interface
described in the SDLs of Q.714 (or similar specifications, such as ANSI
T1.112) to be able to use SUA in a manner transparent to that of SCCP.
Thus, as Barry noted, permitting an implementation of MTP2, MTP3 or SCCP
to present the same interface to the MTP, MTP User, and SCCP User from
M2UA, M3UA and SUA as is presented by a specific implementation of MTP2,
MTP3 and SCCP.  It was considered important to ease implementation of
M2UA, M3UA and SUA within an existing SS7 protocol stack implementation,
as well as a conceptual test of adequacy of the protocol.

However, note that the approach is only applicable to the pure backhaul
case (exporting the SS7/SS7-User interface from SG to ASP).  For the
IPSP and multiple SG as STP scenarios things are somewhat different at
the IPSP and SG.  For multiple SGs as STP, a richer interface is
required at the SG (between the SS7 stack and the NIF) to support the
scenario, and the protocol between the SG and ASPs more closely
resembles an SG-SG interface.  For IPSP the protocol is again different.
SGs as STP requires a higher level of understanding of the specific SS7
network, but is largely a local matter at the SG and how the SG iteracts
with the SS7 network, which is, to some degree, outside the scope of the
specifications.  The statements in the specs about NIF and SG
interactions with the SS7 network are, therefore, largely illustrative.

See, for example, section 4.7.4 in SUA.

--brian

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