Subject: RE: [Diffserv] queue scheduling

From: Sanjeev Chakravarty <[email-masked]>
Date: Wed, 11 Apr 2001 13:19:46 -0700

Hi Tina,
 
The Simulation Results mentioned in the Appendix of RFC2598 (An Expedited
Forwarding PHB) states the following:
 
For Jitter Variation experiment:
 
"   It appears that most jitter for WRR is low and can be reduced by a
   proper choice of the EF queue's WRR share of the output link with
   respect to its subscribed rate.  As noted, WRR is a worst case while
   PQ is the best case. Other possibilities include WFQ or CBQ with a
   fixed rate limit for the EF queue but giving it priority over other
   queues. We expect the latter to have performance nearly identical
   with PQ though future simulations are needed to verify this. We have
   not yet systematically explored effects of hop count, EF allocations
   other than 30% of the link bandwidth, or more complex topologies. The
   information in this section is not part of the EF PHB definition but
   provided simply as background to guide implementers"
 
Other references to such experiments would help establish whether PQ is
indeed the most appropriate queuing mechanism for EF PHB implementation.
 
- Sanjeev Chakravarty

 -----Original Message-----
From: Yuan Lihua [mailto:[email-masked]]
Sent: Wednesday, April 11, 2001 12:06 AM
To: Iliff, Tina; 'Ken'; [email-masked]
Subject: Re: [Diffserv] queue scheduling

----- Original Message ----- 
From: Iliff, Tina <mailto:[email-masked]>  
To: 'Ken' <mailto:[email-masked]>  ; [email-masked]
<mailto:[email-masked]>  
Sent: Tuesday, April 10, 2001 9:54 PM
Subject: RE: [Diffserv] queue scheduling

Ken, 

I have seen documentation that states that several Oss support various
Scheduling mechanisms.  They support DRR, WFQ, Priority Queueing, etc.
However, Priority Queueing has been shown (in studies and experiments) as
the most appropriate for an EF PHB implementation, thus far.

>> Can you refer me which "studies and experiments" that states PQ is the
most appropriate for EF?

Tina Iliff

---

From: Brian E Carpenter <[email-masked]>
Date: Wed, 11 Apr 2001 17:35:09 -0500

Yet again we are getting into territory that belongs
on the implementation list - please continue the
conversation over there folks.
http://www.atnf.csiro.au/news/exploders/dsimplementation.html

Thanks

  Your co-chair

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Brian E Carpenter 
Distinguished Engineer, Internet Standards & Technology, IBM 
On assignment for IBM at http://www.iCAIR.org 
Board Chairman, Internet Society http://www.isoc.org

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