Re: DUNA applies to SG as a whole

Daniel,

Daniel Cohn wrote:                           (Fri, 06 Jan 2006 11:35:34)
> status of each destination on a per-SGP basis.  Is it not possible for
> an SGP to be partially isolated from the SS7 network, such that some SS7
> destinations are reachable and others are not?  Since the SGP generally
> operates in server mode, it cannot simply terminate its SCTP association
> with the ASPs.  The ASPs will try to re-establish.  So, the only way it
> can inform the ASPs that a particular destination is unreachable is via
> the DUNA message.

The proper procedure for partial isolation is unsolicited ASP Inactive Ack
to affected AS.  Yes, the ASP will periodically attempt to reactivate the
AS, as it should.

Sending DUNA for partial isolation is incorrect: it tells all ASPs in the
AS that no SGP in the SG can reach the destination.

> The example redundancy model contained in A.1 suggests that SGPs are
> processes within the same host.  However, this is a restrictive
> definition, and I do not believe it is intended to be taken as normative
> text.  In fact, SGPs are individually addressable, which suggests to me
> that they can indeed exist on separate physical hosts.  In this case,
> the isolation of one SGP from the SS7 network should not be taken to
> mean that the whole SG is isolated.  Since there is no "SGP Inactive"
> message, I see no other way to communicate this type of situation to the
> ASP.

Unsolicited ASP Inactive Ack is effectively an "SGP Inactive" message.

--brian

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