Subject: [Sigtran] M3UA : Unexpected ASP-DOWNACK Message

From: [email-masked]
Date: Sat, 16 Jun 2007 09:20:24 +0800

When ASP and SGP is active status , An ASP-DWONACK Message is received BY
ASP,DO ASP How to Deal with it?

ASP Discard The Meesage? or Send ASP-UP ?

Sending ASP-UP may be  better.

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Sat, 16 Jun 2007 00:28:46 -0600

Chen,

RFC 4666 Section 4.3.4.2 ASP-Down Procedure:

   ...

   At the ASP, the ASP Down Ack message received is not acknowledged.
   Layer Management is informed with an M-ASP_DOWN confirm primitive.
   If the ASP receives an ASP Down Ack without having sent an ASP Down
   message, the ASP should now consider itself to be in the ASP-DOWN
   state.

   If the ASP was previously in the ASP-ACTIVE or ASP-INACTIVE state,
   the ASP should then initiate procedures to return itself to its
   previous state.

   ...

...which would pretty much consist of sending ASP Up.

This behavior was specifically design to permit what we have referred to
as the Unsolicited ASP Down Ack.  The SGP may wish to autonomously send
an Unsolicited ASP Down Ack in the event that it is experiencing an
extensive failure (e.g. local isolation from the NIF) that makes it
impossible for it to serve any AS.  This will drive all AS inactive for
the SGP and cause the ASP to reinitiate the ASP Up procedure.  If the
isolation persists, the SGP may respond to the ASP Up procedure with an
ERR("Refused - Management Blocking") response per section 4.3.4.1 ASP Up
Procedures (below) until the local fault clears.

   ...

   If for any local reason (e.g., management lockout) the SGP cannot
   respond with an ASP Up Ack message, the SGP responds to an ASP Up
   message with an Error message with the reason "Refused - Management
   Blocking".

   ...

Of course, an alternative would be to drop the SCTP association (but
this could result in significantly more message loss.)

--brian

[email-masked] wrote:               (Sat, 16 Jun 2007 09:20:24)

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