Subject: SUA: AS state with multiple SGPs

From: Andrew Booth <[email-masked]>
Date: Mon, 29 Oct 2001 13:26:53 -0500

Hi All,

I'm looking for some clarifications on the SUA case where there are
multiple SGPs in an SG.  Some recent threads have confused me a bit.

The general question is: is AS state maintained per SG or per SGP?  Does
this answer change if all the SGPs may receive SS7 traffic for the same
AS?  To clarify this possibly ambiguous question, here are some specific
scenarios.

In all cases, suppose we have two ASPs ( ASP1 and ASP2 ) and an SG
containing two SGPs ( SGP1 and SGP2 ).  Either ASP may serve the same
AS, that either SGP may receive SS7 messages destined for the AS.

1) Suppose that ASP1 has an SCTP association with SGP1 and is the only
ASP which is active for the AS.
What should happen if an SS7 data message arrives at SGP2, destined for
the AS?
IMO, the messages should be sent to ASP1 through SGP1.  Otherwise the
availability of the AS from an SS7 perspective may depend on the SLS
chosen by the remote node to send the message.  Is this interpretation
correct?

2) Suppose that ASP1 has an SCTP association with SGP1 and is the only
ASP which is active for the AS in override mode.  ASP 2 now establishes
an association with SGP 2, exchanges up and up-ack, and attempts to go
active for the AS (in override mode).  IMO, ASP2 should receive an ASPAC
Ack and ASP1 should receive a Notify that it is no longer active.  Is
this correct?

3) Suppose that ASP1 has an SCTP association with SGP1 and is the only
ASP which is active for RC 1 in override mode.  ASP 1 now establishes an
association with SGP 2, exchanges up and up-ack, and attempts to go
active for RC1.  Should we allow ASP1 to be active on both SGP1 and SGP2
in override mode?

4) Suppose that ASP1 is connected to SGP1 and is active for RC1 is
loadshare mode.  Suppose that ASP2 is connected to SGP2 and is active
for RC1 is loadshare mode.
   i) Should ss7 transfer messages (UDTs) arriving at SGP1 be loadshared
between the ASP1 and ASP2?  Note that SGP1 is not connected directly to
ASP2, so routing traffic to ASP2 involves rerouting through SGP2.  Is
this implementation dependent?
   ii) If SGP2 loses connection to ASP2 it is no longer directly
connected to an ASP which serves the AS.  Should SGP2 move the AS to the
pending state, or should all traffic for the AS simply be rerouted
through SGP1?  IMO, the traffic should be rerouted through SGP1 and the
AS should stay in the Active state.  Is this correct?

5) Suppose that ASP1 is connected to SGP1 and is active for RC1 is
broadcast mode.  Suppose that ASP2 is connected to SGP2 and is active
for RC1 is broadcast mode.
i) Should SS7 transfer messages (UDTs) arriving at SGP1 be broadcast to
both ASP1 and ASP2?

Thanks for any info,
Andrew

-- 
Andrew Booth
Performance Technologies (Ottawa)
(613)237-4284x249
[email-masked]

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