[alcatel-nsp] Question about Service QoS Policies on 7750SR

Mark Griffin Mark.Griffin at hawaiiantel.com
Thu Feb 19 19:00:47 EST 2009

Kila, do you have Ram's book "Advance QoS for Multi-service IP/MPLS
Networks"?  His book does a good job of explaining the behavior of
traffic conditioning in the hierarchal model.



From: alcatel-nsp-bounces at puck.nether.net
[mailto:alcatel-nsp-bounces at puck.nether.net] On Behalf Of Kila Hsu
Sent: Thursday, February 19, 2009 12:44 PM
To: alcatel-nsp at puck.nether.net; GARCIA DEL RIO Diego
Subject: Re: [alcatel-nsp] Question about Service QoS Policies on 7750SR


Thanks a lot, Diego!

I still have several question though. Assume that we don't have a port
scheduler defined, and we do get congestion. As you mentioned, now
queues are transmitted at the physical level using round robin, with
expedited queues being served first.

1. By "queues" do you mean the queue-to-be-transmitted for each SAP? If
there are multiple tier 1 schedulers, or orphaned queues in a SAP, which
one will get transmitted? (or will these queues now become the
candidates for the physical level round-robin?)

2. How are the weights assigned for all these queues? Or is this just an
plain old round-robin with every queue equally weighted?

3. If under each SAP I have hierarchical scheduler, it is possible that
for one SAP, the next packet to be sent comes from an best-effort queue
but the next-next one comes from an expedited queue (although this is a
bad design). In this case, will this SAP have to wait in the physical
level until the expedite queues from other SAPs are transmitted?

I hope I state the problems clearly. Thanks again for all who kindly

Best Regards,
Kila Hsu

--- On Mon, 2/16/09, GARCIA DEL RIO Diego
<Diego.Garcia_Del_Rio at alcatel-lucent.be> wrote:

From: GARCIA DEL RIO Diego <Diego.Garcia_Del_Rio at alcatel-lucent.be>
Subject: Re: [alcatel-nsp] Question about Service QoS Policies on 7750SR
To: alcatel-nsp at puck.nether.net
Date: Monday, February 16, 2009, 1:15 PM

Hi Hsu,


            If your version of TiMOS allows it, you could run a
"port-parent" scheduler, which allows you to map the parent scheduler of
the queues in the SAPs to a port-level scheduler that will distribute
bandwidth between all it's children according to the configured


            If you don't have the port-schduler function (it appeared in
TiMOS 5.0r4 and onwards), sap-queues and schedulers behave "as expected"
when there is no congestion at the port level, that is, all egressing
traffic is less than the port's egress rate.


            If there is congestion though, and no port-scheduler is
configured, queues are indeed served in round-robin fashion with the
"expedited" queues (in in-profile state) being served exhaustively, then
"best-effort" (in-profile) and finally all out-of-profile queues.


            So.. in short, if using TiMOS 5.0 or newer, take a look at
port-level schedulers ;-)




Diego Garcia del Rio
New Product Introduction - Network Design Engineer 
IP Division
Alcatel-Lucent - Antwerpen
Mobile: +32 4734 30 245
OnNET 2 605 3871
Phone (+32) 3 2403871 
e-mail diego.garcia_del_rio at alcatel-lucent.com 

This message (including any attachments) contains confidential
information intended for a specific individual and purpose, and is
protected by law. If you are not the intended recipient, you should
delete this message. Any disclosure, copying, or distribution of this
message, or the taking of any action based on it, is strictly prohibited
without the prior consent of its author.


From: alcatel-nsp-bounces at puck.nether.net
[mailto:alcatel-nsp-bounces at puck.nether.net] On Behalf Of Kila Hsu
Sent: 16 February 2009 16:46
To: alcatel-nsp at puck.nether.net
Subject: Re: [alcatel-nsp] Question about Service QoS Policies on 7750SR


Thanks a lot to Mark for the information about the ways to share a port
among SAPs.
However, my boss seems to like the idea that each SAP can have its own
queues and schedulers though..
So say if I still need to deploy QoS on a per-SAP base, anyone know how
the packets from different SAPs defined on a common port would be
scheduled, if each has its own queue/scheduler?
>From the config guide I do see the "expedite" setting have something to
do with "hardware scheduler", but it is not clear if the setting is used
in cases like this.
Any idea would be appreciated.

Kila Hsu



alcatel-nsp mailing list

alcatel-nsp at puck.nether.net



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/alcatel-nsp/attachments/20090219/bcb3c36a/attachment-0001.html>

More information about the alcatel-nsp mailing list