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

Kila Hsu hsukila at yahoo.com
Mon Feb 23 11:32:10 EST 2009


Thanks for your suggestion. I got this book and read through the queueing and scheduling parts of it. This helps but most of my question still remains.

In Chapter 10 of the book, the idea of dual arbitrator makes sense but it would not be so clear when we have H-Qos and have more than one SAP defined on the same port, or have multiple tier-1 schedulers defined on the same SAP.

In Chapter 11 of this book, the arbitrator idea is not mentioned anymore.. It is assumed that the root scheduler already have the "Obtained bandwidth" but it is not clear to me how the "obtained bandwidth" is calculated. Does this depend on the CIR/PIR defined on the scheduler, or simply by dividing the total BW on the port by the number of tier 1 schedulers, or even other more complex method? I believe the actual schedulers does not divide the bandwidth first then schedule the packets, but rather the BW is the effective value of the result of scheduling. It is very clear to everybody that how the tier one will select a packet from all its child queues when it is allowed to transmit, but it is totally black (for me at least) how the actual port selects which tier 1 scheduler to send next.
>From the previous response from Diego it seems this is again back to the arbitrator, but if anyone knows any more details it would be very nice, since I'm not too confident to deploy this without knowing more details..


--- On Thu, 2/19/09, Mark Griffin <Mark.Griffin at hawaiiantel.com> wrote:
From: Mark Griffin <Mark.Griffin at hawaiiantel.com>
Subject: RE: [alcatel-nsp] Question about Service QoS Policies on 7750SR
To: hsukila at yahoo.com, alcatel-nsp at puck.nether.net, "GARCIA DEL RIO Diego" <Diego.Garcia_Del_Rio at alcatel-lucent.be>
Date: Thursday, February 19, 2009, 7:00 PM





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. 


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;

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 answer!


  Best Regards,

  Kila Hsu


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

  - Antwerpen

  Mobile: +32 4734 30 245

  OnNET 2 605 3871

  Phone (+32) 3 2403871 

  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

  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/20090223/93655f9d/attachment.html>

More information about the alcatel-nsp mailing list