Re: DUNA applies to SG as a whole

Ilie,

Ilie Glib wrote:                                                      (Fri, 06 Jan 2006 19:58:55)
> Dan,
> 
> Draft draft-ietf-sigtran-rfc3332bis-05.txt has the following statement
> 
> 3.4.1 Destination Unavailable (DUNA)
> 
>    The DUNA message is sent from an SGP in an SG to all concerned ASPs
>    to indicate that the SG has determined that one or more SS7
>    destinations are unreachable.  It is also sent by an SGP in response
>    to a message from the ASP to an unreachable SS7 destination. As an
>    implementation option the SG may suppress the sending of subsequent
>    "response" DUNA messages regarding a certain unreachable SS7
>    destination for a certain period to give the remote side time to
>    react. If there is no alternate route via another SG, the MTP3-User
>    at the ASP is expected to stop traffic to the affected destination
>    via the SG as per the defined MTP3-User procedures.
> 
> Thus I believe that in M3UA every SGP upon receiving a message towards
> an unreachable destination sooner or later will answer with a DUNA to
> the ASP. But of couse some traffic can be lost, which can be saved if
> there is another SG with connectivity to the affected SPC.
> 
> Apropo, SUA RFC does not have a statement like "DUNA is also sent by
> an SGP in response to a message from the ASP to an unreachable SS7
> destination"
> So I could imagine an implementation that sends DUNAs from one SGP only.
> 
> 

What is sent to the MTP-User and what the MTP-User expects of the
MTP layer is specified in SS7 standards, not in M3UA.  The bis document
makes statements that are out of scope here and should have moved the
statement to the non-normative appendix.

An SG would be best generate DUNA to each ASP in each affected AS
under the following conditions:

a) In the case where the AS point code is hosted by the SG, DUNA is
   generated under the same conditions that MTP-PAUSE would be generated
   to local MTP-Users are the SG.

b) In the case of the multiple SG as STP configuration, DUNA is
   generated under the same conditions that TFP would be generated and
   sent to the AS point code, were the AS point code a normal SS7 SEP.

Understand?

--brian


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