From: Roy Dempsey (roy.dempsey@gmail.com)
Date: Mon May 30 2005 - 14:12:10 GMT-3
Interesting question. You can change the reserved bandwidth using the
max-reserved-bandwidth, so I don't see why you would need to use the
bandwidth command.
I think you can use WFQ or FIFO in the class-default in theory, not
sure you can use CBWFQ, I keep getting:
R6(config-pmap-c)#bandwidth 40000
Must remove fair-queue configuration first.
R6(config-pmap-c)#
This is regardless of whether I use fair-queue or no fair-queue. But
as I say, I don't see the point.
For the others:
Policing seems to work as it would in any other class
Shaping also seems to work, as long as the service-policy is applied
outbound, like any other class.
Priority doesn't work, as LLQ isn't supported, only FIFO and WFQ (AFAIK).
IMHO, if the traffic is that important don't leave it to fall into the
class-default. Classify it, and put it in a priority queue. Otherwise,
leave it in class-default with 25% of the bandwidth.
Regards,
Roy
On 5/30/05, ccie2be <ccie2be@nyc.rr.com> wrote:
> Hey Roy,
>
> That's what I thought but wasn't sure.
>
> Thanks for confirming.
>
> Come to think of it, there's one other thing I'm not sure about.
>
> By default, the 25% of the bandwidth leftover by the max-reserved-bandwidth
> function assigns that to the class class-default.
>
> That being the case, does it make any sense to use the bandwidth command
> under the default class? Will the IOS even accept the bandwidth command?
>
> And, what about the other policy commands like police, priority, shape, etc.
> I wonder because the default class is where important traffic such routing
> updates and keepalives go, but if a separate class isn't defined for all
> important traffic flows, the default class ends up with a bundle of traffic
> that includes important traffic like routing updates and non-important like
> p2p downloads. Since some of this traffic is important, do you think it's a
> good to shape it or do something else or just leave it with the default
> bandwidth of 25%?
>
> What do you think?
>
> Tim
>
> -----Original Message-----
> From: Roy Dempsey [mailto:roy.dempsey@gmail.com]
> Sent: Monday, May 30, 2005 11:27 AM
> To: ccie2be
> Cc: Firebat; cisco@groupstudy.com; Cisco certification
> Subject: Re: RATE-LIMIT vs POLICE
>
> Tim,
>
> From an IOS point of view, I don't think it regards policing as
> reserving bandwidth in the same way as its does for CBWFQ or LLQ. It
> treats it as more of an absolute limit, with no minimum reservation
>
> A very quick scan of the QoS book seems to confirm this. I tested it
> on a router by setting up a couple of classes with policing enabled,
> and policed over and above the configured bandwidth, and it worked
> fine.
>
> With your config, you won't necessarily be policying at the same time,
> but you most definitely might want to police class A anyway.
>
> So the answer appears to be that your config would work.
>
> Roy
>
> On 5/30/05, ccie2be <ccie2be@nyc.rr.com> wrote:
> > I'm not positive this is what you're asking but if you want to know the
> > difference between rate-limit and police during times when there's not
> > congestion, then the answer is the same.
> >
> > Both rate-limit and police set a maximum amount of bandwidth that can be
> > used and this maximum can not be exceeded regardless of whether or not
> > there's congestion.
> >
> > Be aware, however, that when you use MQC, the most bandwidth that can be
> > reserved is 75% of interfaces' bandwidth.
> >
> > This raises an interesting question:
> >
> > Is the bandwidth specified with the police command in MQC considered
> > "reserved" and applicable to this max-reserved-bandwidth value?
> >
> > IOW, suppose this were the configuration:
> >
> > policy-map TEST
> > class A
> > police 500
> >
> > class B
> > police 500
> >
> > and the bandwidth on the interface is 1000. Will this config work?
> >
> > TIA, Tim
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Firebat
> > Sent: Monday, May 30, 2005 6:39 AM
> > To: cisco@groupstudy.com; Cisco certification
> > Subject: RATE-LIMIT vs POLICE
> >
> > Hi,
> >
> > Can anyone here confirm me? I am thinking that 'RATE-LIMIT OUTPUT' command
> > under interface configuration is always on, regardless there is congestion
> > in
> > outgoing interface. And, 'POLICE' command under class/policy-map
> > configuration
> > will be activated if and only if there is congestion in outgoing
> interface.
> >
> > This thought arise when I face problem to configure router to let Voice
> > traffic can consume 99% link bandwidth, when there is no data traffic.
> But,
> > when data traffic flows, the voice traffic get only 50% bandwitdh.
> >
> > Am I right??
> >
> > Regards,
> > Firebat
> >
> > _______________________________________________________________________
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