Subject: [Sigtran] DAVA came before ASP_ACTIVE_ACK is coreect?

From: 권도형 <[email-masked]>
Date: Fri, 2 Mar 2007 14:18:18 +0900

Dear Sir,

We use SUA Layer. (SG vendor is CISCO).

When our system is up and sends ASP_ACTIVE to SG, SG response with ASP_ACTIVE_ACK.

But SG sends us DAVA messages before ASP_ACTIVE_ACK message.

We discard SNM messages that send before ASP_ACTIVE_ACK.

Should we accept these DAVA messages?

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 1 Mar 2007 22:57:14 -0700

±ÇµµÇü,

±ÇµµÇü wrote:                                 (Fri, 02 Mar 2007 14:18:18)
>    We use SUA Layer. (SG vendor is CISCO).

Please do no use vendor names on this list, particularly as it is
unimportant to the discussion.

>    Should we accept these DAVA messages?

They can be processed, discarded or ignored.  If you assume that all
destinations are accessible anyway, there is no difference.  The sending of
SNMM messages between ASP Active and ASP Active Ack is intended (and only
necessary) to indicate restricted, congested, or inaccessible destinations.

The pertinent passage is RFC 4666/4.5.1:

   For the particular case that an ASP becomes active for an AS and
   destinations normally accessible to the AS are inaccessible,
   restricted, or congested, the SG MAY send DUNA, DRST, or SCON
   messages for the inaccessible, restricted, or congested destinations
   to the ASP newly active for the AS to prevent the ASP from sending
   traffic for destinations that it might not otherwise know that are
   inaccessible, restricted, or congested.  For the newly activating ASP
   from which the SGP has received an ASP Active message, these DUNA,
   DRST, and SCON messages MAY be sent before sending the ASP Active Ack
   that completes the activation procedure.

Nevertheless, it makes sense that it might be necessary to send or process a
DAVA during that period as well (e.g. if a destination becomes available after
the ASP Active is received but before the ASP Active is sent, and possible
after a DUNA has already been sent).

--brian

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