Subject: [SIGTRAN] M2PA - Local Processor Outage/Processor Recovered Proce ssing

From: Hecht Martin <[email-masked]>
Date: Tue, 6 Apr 2004 10:21:58 -0400

To interested M2PA parties,

I have a couple of questions concerning LPO/RPO, LPR/RPR in accordance with
draft-ietf-sigtran-m2pa-11.

I can see the basic relationship between the MTP-2 and M2PA processing of
the Processor Outage conditions.  In MTP-2 there is a short and a long RPO
condition; while in M2PA there is only RPO.

In MTP-2 RPO ends when a FISU or MSU is received; all messages in the TB and
RTB are deleted and the FSN is "reset" at that point, i.e.,
resynchronization occurs.  I can see how this is "mapped" to M2PA.

What I don't see is, referring to pg. 40:

While in LPO, A must buffer messages 14-16 without acknowledging them.

While in RPO, B may continue acknowledging messages.

LPO ends at A.  A flushes 14-16 (the messages that were buffered without
acknowledgement).

Why are 14-16 flushed?  Why were they buffered in the first place?

This means that 14-16 are lost.

On pg. 41:

B flushes 6 from its Receive Buffer.

Why is this buffer flushed?

This means that buffer 6 is lost.

Thanks,
Martin Hecht
Signaling Core Group, Embedded Division
Comverse, Inc

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 6 Apr 2004 14:54:04 -0600

Hecht,

Hecht Martin wrote:                                                                  (Tue, 06 Apr 2004 10:21:58)
> condition; while in M2PA there is only RPO.

Q.703 (MTP2) does not have a short and long RPO concept.  Q.704 (MTP3) has a
short and long RPO concept.

> Why are 14-16 flushed?  Why were they buffered in the first place?

In the example, processor outage is of long term at A, and MTP3 flushes the
messages.  If processor outage were of short term, they would not be flushed.

> This means that 14-16 are lost.

Not necessarily.  Because these messages are not acknowledged to B from A, B
will retransmit these messages on another link as part of the normal
changeover procedure, providing that B does not consider the outage to be of
long term.  If B also considers the outage to be of long term, it will flush
these messages from its RTB.

> Why is this buffer flushed?

For the same reason as above.  When MTP3 at A flushes buffers it flushes RB,
TB and RTB.

> This means that buffer 6 is lost.

Not necessarily, because it was not acknowledged, it could be retransmitted
on another link (processor outage short term) or intentionally flushed
(processor outage long term).

Consider that whether processor outage is of long term or short term is
determined by MTP3 using timer T1 at Level 3, not Level 2.  The example is
one where Q.704/T1 expires at A.

--brian

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