The MPLS-OPS Archive

["M. ELK" <elkou141061@hotmail.com>]

Hi
AFIK

RED (or WRED) is queue mang scheme .
it is algorithm to decide which packet (stored) within the queue to be 
droped .In other word,
queue length control/mang .

WFQ  is Scheduler scheme . ie: Choose which queue to be serviced and for how 
long/much .
reg U question :


Q1. now my question is that it  seems that WRED is supported on the same 
interface as WFQ and we should run both of these queueing algorithms on 
every interface where congestion is likely to occur ie in service provider 
core apply WRED by IP Precedence and WFQ by service class now will there be 
a situation where both WRED and WFQ cannot be supported on the same 
interface???


A1. They are not both Queuing algorithm , only WFQ is queing algorithm .
      WFQ do not apply to service class . WFQ apply to a Queue .
      The classifier function is to classify the incomong packet into 
service class and place the
      packets into the corespending queue .
      may be the syntax of the most used BOX lead U to this conclusion .
      Theoretically U can apply Queue mang and scheduler mang or only one of 
them  .
      In practice , either the two combined or only the scheduler (and use 
tail drop as the default
     queue mang ) .
     Reg applying both to the same interface . this depend on the box 
features .
     also the box could allow U to choose between different Scheduler 
algoritjm
     (WFQ , DRR ..etc ) .
     For queue mang , as far as i know the possible algorithm which U could 
choose from
     is the WRED  or tail drop .

Q2.  or can this problem occur in the future?? or is it occuring now?? .

A2. actually , in the first place Their is no problem to solve .
      In the future , i could guess that extra Queue scheduler Algorithm 
will be avail to choose from .
      also ,extra Queue mang algoritm will be avail to choose from .

Q3.if such a situation would never occur could you people tell me why????

A3. Beacuse we are talking abuut 2 different non competing mang . One handle 
the length of the
     qeue and the other handle which queue to serve . completly unrelated .

Brgds

>From: "subash thyagarajan" <mailsubash@mail.com>
>To: "Irwin Lazar" <ilazar@mplsrc.com>
>CC: mpls-ops@mplsrc.com
>Subject: [MPLS-OPS]: WRED and WFQ
>Date: Sun, 20 Mar 2005 13:16:21 -0500
>

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