Subject: [Sigtran] Traffic distribution semantics

From: "Tolga Asveren" <[email-masked]>
Date: Mon, 27 Feb 2006 10:17:38 -0500

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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---

From: "Barry Nagelberg" <[email-masked]>
Date: Mon, 27 Feb 2006 10:59:58 -0500

Tolga,

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

Barry Nagelberg
Adax, Inc.

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

Any comments/ideas?

    Thanks,
    Tolga

---

From: "Tolga Asveren" <[email-masked]>
Date: Mon, 27 Feb 2006 11:39:14 -0500

Barry,

If it is really implementation dependent, I 100% percently agree with you.
The reason why I thought it could have some interoperability issues is as
follows:

1)Traffic mode allows to effect the message distribution to ASPs. For
example, if one ASP overrides the other one on one SGP, but not the other
one, the traffic they are going to receive will be different, depending on
whether the individual or global state is used in SGPs to distribute the
traffic.

2)I believe it makes sense to send the NTFY for AS state changes based on
the state used for traffic distribution purposes, i.e. if global state is
used based on global state changes, if local state is used based on local
state changes. So, depending on SG is implemented, the NTFYs received by
ASPs will be different.

IMO, neither 1) nor 2) are part of core interoperability, none of the main
procedures will be broken. OTOH, it may create certain issues in real life
deployments. So, I personally am also not thinking strongly that those are
huge problems but tend to think it could be nice to have a common
understanding.

     Thanks,
     Tolga

> From: Barry Nagelberg [mailto:[email-masked]]
> Sent: Monday, February 27, 2006 11:00 AM
> To: [email-masked]
> Subject: RE: [Sigtran] Traffic distribution semantics
>
>
> Tolga,
>

---

From: "Barry Nagelberg" <[email-masked]>
Date: Mon, 27 Feb 2006 12:51:50 -0500

Tolga,

Both #1 & #2 below will be a non-issue once we fix the RFC to clarify that the AS state is kept at a global level across
the entire SG.

I believe that there is a consensus on the mailing list, at least from Brian and Lincoln, that this clarification is
necessary.

Barry Nagelberg
Adax, Inc.

-----Original Message-----
From: Tolga Asveren [mailto:[email-masked]]
Sent: Monday, February 27, 2006 11:39 AM
To: [email-masked]
Subject: RE: [Sigtran] Traffic distribution semantics

Barry,

     Thanks,
     Tolga

---

From: "Tolga Asveren" <[email-masked]>
Date: Mon, 27 Feb 2006 12:40:01 -0500

Barry,

Based on your answer I assume you also consider them as possible
interoperability issue, which needs to be addressed by an official document.

In that case, I think we should be able to answer the questions(and
subquestions like if global AS state is used for traffic distribution, why
is ASPAC sent per SGP etc..) I asked in my first message in this thread and
should be providing an architecturally sound explanation in the RFC.

   Thanks,
   Tolga

> Sent: Monday, February 27, 2006 12:52 PM
> To: [email-masked]
> Both #1 & #2 below will be a non-issue once we fix the RFC to
> clarify that the AS state is kept at a global level across
> the entire SG.
>
> I believe that there is a consensus on the mailing list, at least
> from Brian and Lincoln, that this clarification is
> necessary.
>
> Barry Nagelberg
> Adax, Inc.
>

---

From: "Barry Nagelberg" <[email-masked]>
Date: Mon, 27 Feb 2006 13:08:35 -0500

Tolga,

Your assumption is incorrect. Your concerns are a NON-issue, which will disappear once we update the RFC to reflect the
consensus expressed on the list.

Barry Nagelberg
Adax, Inc.

-----Original Message-----
From: Tolga Asveren [mailto:[email-masked]]
Sent: Monday, February 27, 2006 12:40 PM
To: [email-masked]
Subject: RE: [Sigtran] Traffic distribution semantics

Barry,

   Thanks,
   Tolga

---

From: "Tolga Asveren" <[email-masked]>
Date: Mon, 27 Feb 2006 12:54:19 -0500

Barry,

I think I couldn't express what I mean. I tried to say that you also belive
that traffic distribution and NTFY semantics should be well defined in the
RFC(?).

I also believe RFC should give a good architectural explanation, why traffic
distribution is on a global-AS state basis -based on the majority view-,
where the ASPAC is sent to only one ASP.(the reason why I started this
thread is mainly this)

    Thanks,
    Tolga

> Sent: Monday, February 27, 2006 1:09 PM
> To: [email-masked]
> Your assumption is incorrect. Your concerns are a NON-issue,
> which will disappear once we update the RFC to reflect the

---

From: "Tolga Asveren" <[email-masked]>
Date: Mon, 27 Feb 2006 13:35:44 -0500

Ooooppss typo (again)
where the ASPAC is sent to only one ASP ==>> where ASPAC is sent to all SGPs

> Sent: Monday, February 27, 2006 12:54 PM
> To: [email-masked]

---

From: "Ilie Glib" <[email-masked]>
Date: Tue, 28 Feb 2006 10:12:42 +0100

Hello Folks,

I would like to ask about the consequences of the proposed
clarification on the IPSP - IPSP scenario.

My understanding was that IPSPs when routing outgoing traffic behave
like SGPs and keep the AS states as SGPs do. At the same time I
thought that xxUA adaptation layers in IPSPs are independent in
different IPSPs serving the same AS. Thus these layers do not need to
coordinate their states. (Applications/Users may need to coordinate
their states, but it does not matter in this context)

With the proposed clarification the M3UA layers on IPSPs serving the
same traffic range become dependent on each other and have to
coordinate their states. It is a BIG change to the standard, in my
view. Moreover I do not see a stringent need for this change.

Opinions?

Regards

Ilie

--
Ilie

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 28 Feb 2006 03:04:45 -0700

Ilie,

Ilie Glib wrote:                                                      (Tue, 28 Feb 2006 10:12:42)
> view. Moreover I do not see a stringent need for this change.

I don't see it as a change at all.

--brian

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

---

From: "Tolga Asveren" <[email-masked]>
Date: Tue, 28 Feb 2006 08:22:43 -0500

Ilie,

> From: Ilie Glib [mailto:[email-masked]]
> Sent: Tuesday, February 28, 2006 4:13 AM
> To: Barry Nagelberg
> Cc: [email-masked]
> Subject: Re: [Sigtran] Traffic distribution semantics
>
>
> Hello Folks,
>
[TOLGA]I also think this type of operation -using global-AS state for
traffic distribution semantics- is rather unnecessary and seems to be an
arbitrary choice because I have yet to see a technical argument in its
favor. OTOH, using individual AS states in each SGP allows *all* ASPTM/ASPSM
to be run in each SGP individually, which makes perfect sense and does not
violate the principle of having those procedures between individual
ASPs/SGPs.

As I gather, Greg put some text, because of the my comments 5 years ago,
which I would say not I don't agree at all right now (I was arguing at that
time if AS state is not coordinated, what is the use of concept of SG. Two
points here:
a)At that time, I just was asking about sending NTFYs based on global-AS
state, not using a global state for ASPTM procedures (and now I think even
this is not an issue, because ASP failure information is conveyed with
NTFY("ASP Failure")).

b)If ASPSM/ASPTM is per SGP, concept of SG still makes perfectly sense due
to SSNM, because SG defines a group of SGPs which are visible under a single
MTP3 PC to the network.

Just wanted to share my opinion with you.
> > I believe that there is a consensus on the mailing list, at
> least from Brian and Lincoln, that this clarification is
> > necessary.
> >
> > Barry Nagelberg
> > Adax, Inc.
> >