RE: ASP Capabilities value 0x2 of interworking field

Stanislav,

Just because I will need them for the discussion, I will use the following
terms:

direct forwarding: An entity receives a message and has direct connection to
the destination of the message, so it sends the message to the destination

relaying: An entity receives a message and does not have direct connection
to the destination entity, so sends message to another entity, which may or
may not have a direct connection to the final destination

In the figure, there is no relaying relationship as defined above -probably
I should have put one to cover all cases-.

What I think is as follows:
- When there is direct forwarding between two entities, it is a
client/server relationship, e.g. SGP/ASP. this conceptually is the same as
the vanilla SGP/ASP relationship, where SGP provides SS7 interfacing for
ASP. Actually for SUA, GTT makes SGP/ASP relationship a bit complicated due
to its unidirectional nature, maybe for GTT, one should always go with
relaying approach rather than direct forwarding.
- When there is relaying relationship between two entities, it is a
peer-to-peer relationship on message routing level. I call this SG-SG and as
far as I understand, SUA-relay falls into this category (there is no example
for that in the figure).
- When there is direct and peer-to-peer communication between two
applications, it is an IPSP/IPSP relationship.

Now if I try to answer your question considering the above (although you
refer to App1/App2 I believe you actually mean App1/App3 -between App1/App2
there is direct communication and RC/AS concept is used):
App1/App3 communciation requires GTT. If the need were PC+SSN based
relaying, I would think that the relationship between App1 and forwarding
entity should be SGP/ASP interface, i.e. should utilize RC/AS concept -pleae
note that the forwarding entity has direct connections to both of the
applications-. For GTT, I am not sure. I tend to think, it would be better
to have App1/Forwarding entity interface SG-SG, because GTT itself is
unidirectional. Maybe the best is to use always SG-SG, if there is need for
GTT or any other type of relaying. I am really not sure on that point yet,
OTOH I personally firmly believe that this interface definitly shouldn't be
IPSP/IPSP.


     Tolga




-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of
Stanislav Ivanovich
Sent: Tuesday, December 20, 2005 11:44 AM
To: SIGTRAN
Subject: RE: [Sigtran] ASP Capabilities value 0x2 of interworking field


Tolga,

Are you saying that the AS/RC concept should apply in between SUA at appl1
place and SUA relay point in between appl1 and appl2?

/stanislav



Tolga Asveren <[email protected]> wrote:

[..snip..]
> > [TOLGA]What about in IP domain? The goal with the protocols is
> to define a
> > sound architecture, which allows interoperability and does not
> allow room
> > for ambiguity. IMO allowing IPSP functionality to allow
> relaying is against
> > those principles. I also want to reemphasize that here we are
> speaking of
> > different roles played by SUA stack, i.e. we can have SUA-node which can
> > both relay and use IPSP communication. What we are discussing ! is,
where
> > those different functionalites should reside.
>
> Functional placement is an implementation issue.
To clarify what I mean, consider the following figure (SUA stands for SUA
functionalities, it does not refer to any specific implementation, e.g. it
can be one or more than one stack instance)

 +-------+
 | App4  |
 +-------+
 |  SUA  +            +-------+              +-------+
 +--+----+            | App1  |              | App2  |
    |    SGP/ASP      +-------+              +-------+
    +--procedures-----+  SUA  +---IPSP-------+  SUA  |
             +--------+--+----+   procedures +-------+
             |           |
           SGP/ASP       |
 +-------+ procedures  SGP/ASP
 | App5  |   |         procedures
 +-------+   |           |
 |  SUA  +---+           |                   +-------+
 +-------+               |                   | App3  |
                      +--+----+              +-------+
                      |  SUA  +---SGP/ASP----+  SUA  |
                      +-------+   procedures +-------+

Let's suppose for App1/App2 communication, there is no need for GTT -nor for
any other type of relay-, so IPSP procedures are used.

For App1/App3 communication we need GTT, so! messages are sent from App1 to
an entity which can perform GTT and relay. For that communication SGP/ASP
procedures are used.

Let's suppose the node hosting App1 performs certain GTT functions as well
and they are used for communication between App4/App5. In this case, again
SGP/ASP procedures will be used.

This, IMO allows a clean separation between interfaces used for different
purposes.



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