RE: Traffic distribution semantics

Tolga,

This subject is implementation dependent and doesn't belong in the RFC.

Barry Nagelberg
Adax, Inc.

-----Original Message-----
From: Tolga Asveren [mailto:[email protected]]
Sent: Monday, February 27, 2006 10:18 AM
To: [email protected]
Subject: [Sigtran] Traffic distribution semantics


After much discussion in "M3UA Notify Message" thread, I got more confused
and became unsure regarding what needs to be done (I wanted to start a new
thread because I doubt many people followed it and I can't blame anybody, it
probably should be an off-line discussion for most of the time)

The question to be answered is who is the owner of the traffic distribution,
SG or SGP -here as traffic distribution, I refer to traffic distribution
from M3UA point of view, selecting an ASP depending on loadshare or override
traffic modes-. Practically it means, do we distribute traffic to ASPs based
on the "global ASP states" kept SG-wide or the "local ASP states" kept in
each SGP individually? If global ASP state is used, SG would be the owner of
traffic distribution, if local state is used, SGP would be the owner of
traffic distribution.

I believe there are two main parameters to be considered:
a)Are traffic characteristics different on SGPs belonging to the same SG
b)The architectural robustness/elegance

For a), the question to be answered is are messages coming from different
SGPs -in the context of this discussion, all SGPs in consideration are part
of the same SG- treated in a different way at an ASP/have different
preference. At the first thought, my answer was "No" but I am not ruling out
the possibility that things like geographical location could be a parameter
here, where it would be desirable/preferrable to receive traffic from
certain SGPs and not so preferred from other ones, for example due to the
cost of IP routing.

For b), the question of ownership of traffic distribution to ASP question
leads to who is the owner of ASPTM procedures. It doesn't sound very clean,
to have different owners for traffic distribution and ASPTM. Actually
traffic distribution itself is an ASPTM procedure. Considering this, one
would expect all logical execution associated with ASPTM to happen at the
same entity. I would expect ASPSM to be executed at same entity as well from
architectual sanity point of view. Practically this means, if SG is owner of
the traffic distibution, why is it not owner of ASPTM (and possibly ASPSM)
as well? Why is ASPAC sent to all SGPs, rather than just to one of them? One
could even ask why is ASPUP sent to all SGPs, rather than to only one?

I believe, from "necessity" point of view, we need to consider the answer
for a). If the answer for a) is "characteristics are not different for
messages coming from different SGPs", then for b) both options are open.
There is no exact need to send ASPAC to all SGPs. In such a case I would
expect all  ASPTM procedures -including traffic distribution- to be executed
based on the states kept per SG or per SGP but not in a mix-match way. In
this situation, my preference would be using states kept in each SGP,
providing a more simplistic architecture, where all ASPSM/ASPTM is executed
in the context of a single SGP -please note this does mean disallowing
internal routing or not creating a uniqie SPMC view-.

If the answer to a) is "Yes", then it seems preferrable to have traffic
distribution logic to use states kept in individual SGPs, because this would
allow ASPs, to force different choices on different SGPs, depending on their
needs. In this case I would expect all ASPTM to use states kept in
individual SGPs.

Any comments/ideas?


    Thanks,
    Tolga




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