Subject: RE: [Sigtran] ASP Identifier

From: "Goel, Soni" <[email-masked]>
Date: Wed, 27 Feb 2002 11:50:46 -0800

Hi,
Please see my comments below.
- Soni

-----Original Message-----
From: Brian F. G. Bidulock [mailto:[email-masked]]
Sent: Tuesday, February 26, 2002 6:03 PM
To: Goel, Soni
Cc: Sigtran (E-mail)
Subject: Re: [Sigtran] ASP Identifier

Soni,

An ASP Identifier is used for two things: (1) to identify
an ASP when connecting to an SGP when no other mechanism
(e.g, IP address and port number) can distinguish between
ASPs; and, 

[Soni] Does it mean multiple ASPs having same IP address and same port
number ? That is something wierd.

(2) to identify to other ASPs connected to the
same SGP which ASP has failed in a NTFY("ASP Failure").

To serve both purposes, the ASP Id of an ASP must uniquely
identify the ASP to an SGP.  So, it could be provisioned on
as much as a per ASP/SGP relation: that is, on an SCTP
association basis.

What makes you think it must be unique to an AS?  It does
not appear with RC in any messages...

[Soni] Because M3UA draft states the following -
"The optional ASP Identifier parameter contains a unique value that is 
locally significant among the ASPs that support an AS."

--brian

Goel, Soni wrote:                                           (Tue, 26 Feb
2002 16:50:43)
> Hi,
> 
> What is the scope of uniqueness of ASP Id? Should it be unique per AS or
for
> the whole network ?
> 
> - Soni
> 
> _______________________________________________
> Sigtran mailing list
> [email-masked]
> https://www1.ietf.org/mailman/listinfo/sigtran

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

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---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 27 Feb 2002 15:50:18 -0600

Soni,

Please see comments below...

Goel, Soni wrote:                                           (Wed, 27 Feb 2002 11:50:46)
> number ? That is something wierd.

No.  It means multiple ASPs having the same IP address and
different point numbers, but the port numbwer are dynamically
assigned by the ASPa and the SGP cannot use port number to
distinguish between the ASPs.

This is a very common arrangement for both TCP and SCTP.  The
SGP is listening on the well-known port number (2905) and the
ASP connects with a dynamically assigned port number.

For example, when you browse the web, you connect to the server
on port 80, but your computer dynamically assigns a port number
to the connection.

The same is true for SCTP.  When multiple ASP processes on a
host connect to the SGP port number 2905, it is quite normal
to dynamically assign ASP port numbers to each process.  Thus
there can be two ASPs connecting to the SGP from the same host,
but the SGP cannot distinguish between them.  To accomplish
this the ASP sends the ASP Id in these circumstances to permit
the SGP to distinguish between the ASPs.

> locally significant among the ASPs that support an AS."

ASPs that do not support an AS are not very useful ASPs. :)

It is significant to a group of ASPs because when the an
ASP receives an ASP Id in NTFY("ASP Failure") it needs to be
able to determine to which ASP the NTFY pertains.  This, however,
can still be accomplished with an ASP Identifier which is unique
to the SGP/ASP relation (SCTP association) because the ASP knows
on which association the NTFY was received.

In general this is accomplished at the SGP. That is, each ASP
connecting to the SGP must have a unique ASP Id (either in the
ASPUP or from local determination based on IP addresses and
stuff).  The connection ASP should also know the identifier of
other ASPs connecting to the same SGP in which it is interested.
When the SGP sends the NTFY, it uniquely identifies the ASP
to which SGP/ASP communication has failed to the other connected
ASPs.

It is rather very simple.  Is it clear to you now?

--brian

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