Subject: [Sigtran] Congestion Control in M3UA

From: [email-masked]
Date: Mon, 14 Oct 2002 16:16:54 -0400

All:

I'm curious about congestion control procedures in the M3UA RFC.  The RFC
and implementor's guide state that the SG is expected to maintain
congestion status.  When the SG detects the onset of congestion, SCONs
containing the appropriate congestion level are broadcast to the M3UA peer.
Following that, the peer may then respond by polling with DAUDs.  The SG
then responds with SCONs with the current congestion status.

As congestion levels change or congestion abates (for national
destinations), is the SG expected to send autonomous SCONs with the
appropriate status (if congestion has abated the status would be 0) to the
all national ASPs that had been originally been notified of the congestion
onset?  Understandably if the M3UA peer requests status with a DAUD, the SG
must respond.  However, if the peer does not request status, how is the
peer notified of either congestion abatement or status updates or is the
peer even notified of abatement via a SCON-congesion-level-0 message?  If
the SG autonomously broadcasts congestion status updates to all national
destionations, will unaffected peers simply discard the message(s)?

Regards,
Mark Erickson

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From: Tolga Asveren <[email-masked]>
Date: Mon, 14 Oct 2002 16:35:56 -0400

Mark,

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
> Sent: Monday, October 14, 2002 4:17 PM
> To: [email-masked]
> Subject: [Sigtran] Congestion Control in M3UA
> 
> 
> 
> All:
> 
> onset?  Understandably if the M3UA peer requests status with 
[TOLGA] IMO, yes.
> a DAUD, the SG
[TOLGA] As you stated, whenever congestion status changes, SG can report it
to relevant ASPs. I think, SG has enough information to decide, which ASPs,
it should send SCONs to, so it would be more elegant not to send SCON to
unaffected ASPs. IMO, when there is congestion status change because of
congestion status change on local links, sending SCON to all ASPs is fine.
When SCON should be generated because of a received TFC or because of route
set congestion procedure itself (T16 expiry), IMO sending SCON just to the
relevant ASPs is a better solution.