Subject: RE: [Sigtran] SG view of the ASP

From: "Munnaluru, Krishna" <[email-masked]>
Date: Thu, 9 Feb 2006 16:56:42 -0600

Brian,

Yes. The SGP sent a NOTIFY with Alternate ASP Active. In reality there
is only one ASP.

Thanks,
Krishna

-----Original Message-----
From: Brian F. G. Bidulock [mailto:[email-masked]] 
Sent: Thursday, February 09, 2006 2:39 PM
To: Munnaluru, Krishna
Cc: [email-masked]
Subject: Re: [Sigtran] SG view of the ASP

Krishna,

Munnaluru, Krishna wrote:                    (Thu, 09 Feb 2006 13:51:56)
> The ASP is currently sending the ASP UP message with the same ASP Id
to
> both SGPs. 
> 
> As per the SG guys suggestion we temporarily changed the ASP
trafficmode
> in the ASP ACTIVE message to loadsharing and this problem goes away.
But
> we see another problem.
> 
> The administrator on the ASP side decides to take down the SCTP
> association with SGP2. The ASP sends ASP DOWN message to the SGP2.
Then
> the SGP2 responds with ASP DOWN ACK. So far everything looks good. But
> then immediately the SGP1 sends a NOTIFY with the status=ASP Failure
and
> includes the Routing Context value. Why is the SGP1 sending this
NOTIFY
> and what is the expected behavior of the ASP upon receiving the NOTIFY
> from the SGP1? The SG is sending the NOTIFY because it treats the ASP
as
> two separate ASPs and so it thinks that it is notifying to the other
> ASP.
> 
> I think it came down to the way SG was designed - "The SG treating
each
> association as a separate ASP as supposed to just one ASP with two
> associations".  Is this the general way a SG behaves (or designed)?
> Should it not treat an ASP as just one rather than two?

In the override case, did the SG send NTFY("Alternate ASP Active") when
SGP1 marked the ASP ASP Inactive?  If not, the SG is not behaving
consistent
with the view that there are two ASPs.

--brian

> 
> Please provide some input so that I can confirm my understanding of
the
> M3UA protocol.
> Thanks,
> Krishna

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

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---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 9 Feb 2006 16:16:58 -0700

Krishna,

Well, that likely explains the NTFY("ASP Failure") in loadshare mode
too.

When SGP1 in loadshare mode sends an NTFY("ASP Failure") as you describe
below, does it include an ASP Id? (It is required to if an ASP Id was
provided in the ASP Up for that ASP.)  If so, it is indeed ignoring ASP
Id and telling the (attached) ASP that the ASP with the same id as it
has failed, which does not make much sense.  It really appears that the
implementation has some problems.  You might be able to find a few test
cases in one of the interop test plans that can illustrate the errors in
the implementation to its builders.

I have a few of the interop test plans posted starting here:

  http://www.openss7.org/sigtran.html

if that will help.  I recall some cases testing multiple ASPs and
multiple SGPs in various traffic modes.  Unfortunately the examples in
the specs show one SGP and multiple ASPs.  I think that it would make
sense to formalize a test spec for M3UA and SUA and publish them as
informational RFCs, serving to provide both examples and testing
suggestions.

--brian

Munnaluru, Krishna wrote:                    (Thu, 09 Feb 2006 16:56:42)

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