Subject: Re: [Sigtran] [m3ua]-AS-SG

From: "TOLGA ASVEREN" <[email-masked]>
Date: Tue, 4 Mar 2003 11:13:34 +0200

Brian,

Again briefly my opinion about this topic:
-One SGP can be part of only one SG (if clarification is necessary, then
let's add it and it should be noted that current M3UA procedures do not
support such a configuration)
-I don' t see a need to make any change to make it possible that SGPs can
be  part of multiple SGs.

Please see some further comments below.
   Tolga

TOLGA,

TOLGA ASVEREN wrote:
(Tue, 04 Mar 2003 09:31:09)
>
> Brian,
>
>
> TOLGA ASVEREN wrote:
> (Tue, 04 Mar 2003 07:58:04)
> >
> > Brian,
> >
> > My point with my explanation why each SGP can be identified only with
> SCTP
> > addressing from ASP point of view was not to propose implicitly to put
a
> > parameter or to define a procedure to do otherwise. IMO, there is no
need
> > for this. Just form two SCTP associations -one for each SGP-, I don't
> think
> > this is terribly bad.
> > Still some comments below.
> >
> >     Tolga
> >
> >
> >
> > Barry.Nagelberg,
> >
> > [email-masked] wrote:
> > (Mon, 03 Mar 2003 13:08:15)
> > > "Brian F. G. Bidulock" <[email-masked]>
> > > Sent by: [email-masked]
> > >  03/03/2003 12:37 PM
> > >  Please respond to bidulock
> > >
> > >
> > >         To:     [email-masked]
> > >         cc:     [email-masked]
> > >         Subject:        Re: [Sigtran] [m3ua]-AS-SG
> > >
> > >
> > > Barry.Nagelberg,
> > >
> > > [email-masked] wrote: (Mon, 03 Mar 2003 11:18:26)
> > > > Brian,
> > > >
> > > > OK, I agree with you that a parameter to identify the SG could be
> > > selected
> > > > on an implementation-dependent basis. This, however, would destroy
> the
> > > > concept of  interoperability.
> > >
> > > How so?
> > >
> > > [BN] - Because both the ASP and the SGP must be aware that the chosen
> > > parameter is being used to identify the SG.
> >
> > I don't think so...  Why would the ASP need to know that the SGP is
> > using SLS, for example, to select the SG?
> > [TOLGA]If ASP is communicating via multiple SGs, it should be able to
> > select the SG it wants, reachability of a specific destination might be
> > different via each of them.
>
> Where does it say that in the RFC?  (That the AS SHOULD be able to select
> an SG???)
> [TOLGA]If there are multiple SGs in the configuration, I think it is very
> clear that ASP has to select a SG for outgoing traffic. In fact it also
> shoud decide from which SG a message is coming from(for SSNM for
example).

Where is the requirement in the RFC?
[TOLGA]Then please tell me how it is supposed to work according to you?
Because RFC tries to handle every scenario (single SG/multiple
SG/backhaul/non-backhaul) it is no suprise to me that no "SHOULD" is
present about this(or maybe nobody thougth that this is necessary to say.
BTW please note that for ASP it is said that it might process traffic
related with more than one AS, whereas for SG/SGP there is no such
statement.)

>
> > This basically also rules out any possiblity to use SLS for that
purpose.
>
> I don't see it ruled out at all.  I personaly don't think that it would
be
> terribly useful, but it is not ruled out.
> [TOLGA]It is ruled out. Please see example in my original message. How
will
> SGP1 handle such a scenario?
>
> > Imagine the scenario where ASP1 uses SG1 and SG2.  PC-A is reachable
via
> SG1
> > but not via SG2.
>
> Who says this has to happen?  The reachability of all remote point codes
> via
> SG1 and SG2 could be identical.  Don't assume that they are mated STPs.
> [TOLGA]The example assumes that SGP acts as part of multiple SGs with
> different MTP3.

Where does it say that different SGs have to have different MTP3?
[TOLGA]Otherwise, what is the logic of to have multiple SG?

> So, nobody can assure that they will have always the same SS7
connectivity.

Yes you can, by configuration.
[TOLGA]Then why do you have multiple SG? And is it a good idea to base the
mechanisms on some assumptions/specific configurations?

> I think, what you are doing is an assumption -that those SGs *with
different
> MTP3* have the same reachability inormation about destinations-.

Where does it say that different SGs have to have different MTP3?  SGs
could
be partitions of the same MTP3, or might even have no MTP3 at all.
[TOLGA]Why would one want to have separate SGs, if they are going to use
the same layer3 entity? This is not logical and is useless IMO, to have two
logical entities consisting of totally same physicall entities. In such a
case, they are the same logical entity, i.e. the same SG.

> But as I indicated before, this example relies on the wrong interpreation
> what SGP is, i.e. it excludes MTP3 part and assumes SGP is just M3UA-SGP.
> This is not my view of SGP.
>
>
> > And let's furthermore assume one wants to use just SGP1 for
> > both SG1 and SG2. Now there is one association between SGP1 and ASP1
> -O.K.
> > this won't work, but the point is to show that it won't work with one
> > association-. ASP1 wants to send messages to PC-A and because it is
> > reachable via SG1 and because SGP1 is part of SG1 it sends the messages
> to
> > it. Now let's assume SGP1 is doing loadsharing based on SLS to decide
for
> > which SG (SG1 or SG2) the message is intended for. In such a case
> messages
> > with SLS values matching SG2 will be dropped.  Now, one might argue
that
> > when one speaks of SGP, it also includes level3 logic (MTP3) not just
> > M3UA-SGP stack (this is how I see it and IMO also how RFC sees it and
> please
> > note the above example does not interprete SGP in that way). In such a
> case,
> > by definition, one SGP can't be part of multiple SGs(countability
> argument
> > in your message, I agree).
>
> I asked how to count them.  Do you believe that they must be different in
> SS7
> routing to count them?  I appears so.  I don't see where it says that in
> the
> RFC either.
> (TOLGA]In the RFC you can't find it, because there SGP is both M3UA +
MTP3
> and so one SGP can be part of only one SG.

Not forbidden in the RFC?  Then it is permitted.  Why say it is not?
[TOLGA]IMO it is not permitted, because on ASP side one can't decide, from
which SG a message is coming from and similarly on SGP side, to which SG a
message is sent(by staying within the boundaries of RFC and in an
interoperable way).

_______________________________________________
Sigtran mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/sigtran

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 4 Mar 2003 03:15:48 -0700

TOLGA,

TOLGA ASVEREN wrote:                                                                 (Tue, 04 Mar 2003 11:13:34)
> [TOLGA]Otherwise, what is the logic of to have multiple SG?

It is one thing to say that SGP must be part of only one SG.  It is completely
a different thing to say that an SG must have different MTP3 than another.

> mechanisms on some assumptions/specific configurations?

Operational considerations.

> case, they are the same logical entity, i.e. the same SG.

When providing virtual SS7 networking it is often advantageous to have
multiple logical entities in the same physical entity.  It also has use
for mediation and network partitioning.

> message is sent(by staying within the boundaries of RFC and in an

How does an ASP know what SG (or SGP for that matter) it is connecting to?
There is no SGPID in any message.

--brian

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