From: Chris Lewis (chrlewiscsco@gmail.com)
Date: Wed Jan 11 2006 - 16:00:46 GMT-3
Oopos a little math error there, 4+6+5 is indeed 15 not 14 as I wrote. The
logic is correct though, any weight applied to queue 4 when teh
priority-queue out is also configured is disregarded.
Chris
On 1/11/06, de Witt, Duane <duane.dewitt@siemens.com> wrote:
>
> Hi
>
> I'm a little confused with this one. If the priority queue is excluded
> then the weights are 4+6+5 = 15. Q1 should be 25% of 15 which is 3.75
> rounded to 4. Q2 should be 30% of 15 which is 4.5 rounded to 5. How does
> the solution get to 6?
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Chris Lewis
> Sent: 11 January 2006 04:47 PM
> To: Nick
> Cc: ccielab@groupstudy.com
> Subject: Re: wrr-queue bandwidth command
>
> Nick,
>
> A good post, but I think one point of detail may be lost here. I think
> the
> point of detail is missed both in the original question and in the
> answer
> provided. So I think the person that wrote the requirement was missing a
> point of how priority-queue out works.
>
> The priority-queue out command configures the 3550 to use strict
> priotity
> scheduling for transmit queue 4. This means that any weighting assigned
> to
> queue 4 by the wrr-queue bandwidth is meaningless, as if there is any
> traffic in queue 4, it will be transmitted regardless of weighting
> configured for that queue. In essence, when priority-queue out is
> configured, the bandwidth allocation algorithm ignores weightings
> assigned
> to queue 4. The documentation for the priority-queue out command states
> the
> following:
>
> "When you configure the *priority-queue out* command, the weighted round
> robin (WRR) weight ratios are affected because there is one fewer queue
> participating in WRR. This means that *weight4* in the *wrr-queue
> bandwidth*interface configuration command is ignored (not used in the
> ratio
> calculation). The expedite queue is a priority queue, and it is serviced
> until empty before the other queues are serviced. "
>
> This is how it looks on a switch. I configure F0/1 as given.
>
> interface FastEthernet0/1
> switchport mode dynamic desirable
> wrr-queue bandwidth 4 6 5 5
> wrr-queue cos-map 1 6 7
> wrr-queue cos-map 2 0 1 2
> wrr-queue cos-map 3 4 5
> wrr-queue cos-map 4 3
> priority-queue out
> end
>
> Now I look at the following show command.
>
> Switch#sho mls qos int f0/1 queueing
> FastEthernet0/1
> Egress expedite queue: ena
> wrr bandwidth weights:
> qid-weights
> 1 - 4
> 2 - 6
> 3 - 5
> 4 - 5 when expedite queue is disabled
> Cos-queue map:
> cos-qid
> 0 - 2
> 1 - 2
> 2 - 2
> 3 - 4
> 4 - 3
> 5 - 3
> 6 - 1
> 7 - 1
>
> The important part to note is that queue 4 will have weighting 5 only if
> the
> expedite queue is disabled.
> What the configuration given means is that traffic in queue 4 will take
> whatever it wants, then the remaining queues will have bandwidth
> allocated
> as follows, as any weighting assigned to queue 4 when the priority-queue
> out
> command is configured, is ignored:
>
> Q1: 4/14 - (the figure 14 coming from the sum of weights fro queue 1,
> 2, 3)
> Q2: 6/14
> Q3: 5/15
>
> Now if I take off the priority-queue command, all your math looks
> correct to
> me, as verified by the output below:
>
> Switch(config)#int f0/1
> Switch(config-if)#no priority-queue out
> Switch(config-if)#do sho mls qos int f0/1 que
> FastEthernet0/1
> Egress expedite queue: dis
> wrr bandwidth weights:
> qid-weights
> 1 - 4
> 2 - 6
> 3 - 5
> 4 - 5
> Cos-queue map:
> cos-qid
> 0 - 2
> 1 - 2
> 2 - 2
> 3 - 4
> 4 - 3
> 5 - 3
> 6 - 1
> 7 - 1
>
> Chris
>
>
>
> On 1/11/06, Nick <seajay76@nate.com> wrote:
> >
> > Please disregard the last strange mail.
> >
> > (1) With the priority-queue out, the 4th queue of the interface
> becomes
> > the expedite queue.
> >
> > int fa0/4
> > priority-queue out
> >
> > (2) you need to put the COS-3 packet int eh 4th queue
> >
> > int fa0/4
> > wrr-queue cos-map 4 3 (they are the queue number and the CoS in order)
> >
> > (3) Then you can use the other remaining 3 queues.
> >
> > (4) Allocate the designated bandwidth to the queues.
> >
> > int fa0/4
> > wrr-queue bandwidth 4 6 5 5
> >
> > Here 4 means 4/(4+6+5+5) , 6 means 6/(4+6+5+5) , 5 means 5/(4+6+5+5)
> >
> > So you might put it this way.
> >
> > int fa0/4
> > wrr-queue bandwidth 20 30 25 25
> >
> > (5) Since you allocate the bandwidth to the queues,
> > just put the CoSed packets in each queue
> > You did it for the fourth queue already in (2)
> >
> > int fa0/4
> > wrr-queue cos-map 1 6 7
> > wrr-queue cos-map 2 0 1 2
> > wrr-queue cos-map 3 4 5
> >
> > HTH~~
> >
> > Regards,
> > Nick
> >
> > ----- Original Message -----
> > From: <Bill.McKenzie@bisys.com>
> > To: <ccielab@groupstudy.com>
> > Sent: Wednesday, January 11, 2006 10:17 PM
> > Subject: wrr-queue bandwidth command
> >
> >
> > > Here is the requirement :
> > > Cos-3 must be sent of everything else and match the following cos
> values
> > to
> > > according bandwidth.
> > >
> > > Cos 3 = 25%
> > > CoS 6,7 = 20%
> > > CoS 0,1,2 = 30%
> > > CoS 4,5 = 25%
> > >
> > > Here is the solution:
> > >
> > > wrr-queue bandwidth 4 6 5 5
> > > wrr-queue cos-map 1 6 7
> > > wrr-queue cos-map 2 0 1 2
> > > wrr-queue cos-map 3 4 5
> > > wrr-queue cos-map 4 3
> > > priority-queue out
> > >
> > >
> > > I don't understand the values in the wrr-queue bandwidth command and
> > trying
> > > to look at the doc cd is just confusing me more. Can anyone point me
> to
> > a
> > > better explanation of how the values were estimated?
> > >
> > > Thanks,
> > > Bill
> > >
> > >
> > >
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