Subject: RE: [Sigtran] Another Congestion/SCON Question

From: "Richard Adams" <[email-masked]>
Date: Thu, 5 Dec 2002 15:18:44 +0100

Brian,
Pls see below.
-----Original Message-----
From: Brian F. G. Bidulock [mailto:[email-masked]]
Sent: 05 December 2002 14:42
To: Richard Adams
Cc: [email-masked]; [email-masked]
Subject: Re: [Sigtran] Another Congestion/SCON Question

{snip}
> How user traffic is restarted would be a nodal implementation
dependent
> matter if user and MTP were co-located, as in SS7, so perhaps for ITU
it
> doesn't matter. But where the user is remote, I think needs to be
> sorted-out! {RAA} 

Its clear from Q.714 how traffic is to be restarted.  It is also
clear that Q.764 ignores congestion indications in MTP-STATUS
(particularly because ISUP normally throttles with ACL). 
{RAA} For ITU-like ISUP, a number of congestion levels (implementation
dependent) are defined, and a timer nominally a few seconds (5 I think)
runs. Traffic is reduced dependent on the level recorded in ISUP. Each
congestion indication from the MTP (for the international 1 level
scheme) causes an increment to the ISUP level, and a restart of the
timer. Expiry of the timer causes a decrement and a restart of the timer
if ISUP level > 0. 
So ISUP works OK for me (but maybe not for T1 !) {RAA}

T1.113 also ignores congestion in MTP-STATUS.  T1.112 passed it to the
SCCP user in N-PCSTATE (the procedures which are left for further
study in TCAP).
{RAA} When I was working with 3G - like protocols, they were considering
doing "something" beyond TCAP. So.. {RAA}
So, Q.714 is the only one that goes about describing it, and, although
it has the optional level in the MTP-STATUS, it ignores congestion
status 0 and all abatements (will discard while the timer is running
and will decrement when it expires).
{RAA} Because it's only describing the international method. Multiple
MTP levels are for further study! {RAA}
So it doesn't appear that there is a user that can use a status
indication of 0 even if you were to send it.

Rewriting the rules of the MTP-User is well outside the scope of
M3UA work.

So, let's leave it a SCON(0) being OPTIONAL (which it is in the
RFC anyway).  Any disagreement?

--brian

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

{RAA} Fine by me. Thanks.
Kind regards,
Dick

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---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 5 Dec 2002 09:52:01 -0700

Richard,

Richard Adams wrote:                      (Thu, 05 Dec 2002 15:18:44)

> So ISUP works OK for me (but maybe not for T1 !) {RAA}

Do you have an ITU-T (or any) reference for this procedure for ISUP?

--brian