Subject: M3UA08: Client/Server Model

From: Hong Liu <[email-masked]>
Date: Wed, 8 Aug 2001 19:50:22 +0200

Hi, all,

I have a question for clarification regarding the failure recovery in
M3UA08. In Section 1.4.8, it specifies that peer endpoints SHOULD be
configured that one always takes on the server role while the other
always takes on the client role. And the client SHOULD always initiate
the SCTP association setup.

Suppose the server, say an SGP, goes down and comes back up again. Will
it be the SGP to re-established SCTP associations with each of the ASPs
it is configured to communicate? A similar situation arises when a new
SGP is activated and join the pool of SGPs.

Thanks in advance!

--Hong

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Fri, 10 Aug 2001 01:10:25 -0500

Hong,

Following the SHOULDs, where the SGP is server, the SGP SHOULD wait for
the ASP to initiate a connection to it, both on initial boot and after
an association failure.

If you don't follow the SHOULDs, the SGP as server could attempt to
initiate connections both at boot and after failure, it if knows the
IP/port numbers associated with the ASP, or otherwise knows how to go
about contacting a particular ASP.

Where the ASP is dynamically assigning port numbers, this might be
difficult for the SGP to pull off.  Unless the ASP, say, is also
configured as server and is listening on the well-known port number for
the UA.  The ASP Id parameter now permits the ASP to identify itself to
the SGP in either case, so perhaps these SHOULDs are a little weaker
than they originally needed to be.  For ASPs using ASP Id or purely
static port assignment arrangements, there is certainly no need to
configure one side as server and the other as client.  Both sides coule
attempt and reattempt until one successful connection has occured.  In
the ASP Id case, it is easily detected at both the SGP and ASP whether
there is a second association being attempted to the same SGP.  In the
static configuration case, both sides will use the same port pairing and
dual init attempts will be coalesced to a single association.

I don't know whether the drafts should say SHOULD here anymore.
Perhaps this should be downgraded to MAY.

--brian

Hong Liu wrote:                                 (Wed, 08 Aug 2001 19:50:22)

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

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