From: Yasser Aly (blackyeyes00@hotmail.com)
Date: Wed Feb 18 2004 - 17:26:53 GMT-3
Hi Brian,
I have two more questions and need your help with.
1) Why wouldn't the Committed Burst in this example set to be 6000 instead
of 4000 to be consistent with what Cisco says in this link
==============
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fqos_r/qrfcmd8.htm#1037428
Policing Traffic with CAR
CAR embodies a rate-limiting feature for policing traffic. When policing
traffic with CAR, Cisco recommends the following values for the normal and
extended burst parameters:
normal burst = configured rate * (1 byte)/(8 bits) * 1.5 seconds
extended burst = 2 * normal burst
=================
Based on this I would calculate it as follows:
Normal Burst= (128000/8)*1.5= 24000 and the required is 1/4 this value so
the answer would be
6000. And then as Be is not required so to be set by the smallest possible
value.
Be in this case would be 6000
2) If I am asked to set CAR with no restrictions and just follow Cisco
recommendations.
For example required CIR = 1M
Would it be correct if I set it up as follows
rate-limit input 1024000 192000 384000 conform-action transmit
exceed-action drop ??
How about if the requirement was not to allow excess burst at all would this
be correct
rate-limit input 1024000 192000 192000 conform-action transmit exceed-action
drop ??
Thanks for your feedback.
Regards,
Yasser
>From: "Brian McGahan" <bmcgahan@internetworkexpert.com>
>
> > >So, 128,000 kbps dvided by 8 = 16,000 = bits per interval, Tc. To
>allow
> > >for a burst of 1/4 of this rate, divide by 4. 16,000 / 4 = 4000.
>
> Yes and no. The interval is determined by what you configure. Your
>target rate is 128000, which is entered in bits per second. The burst
>committed value, which comes next, is in bytes per interval. Since it is
>specified that the burst should be a quarter of the target, the rate is
>(128000/8)/4 = 4000.
>
> The reason that the Be is 4000 is that there is no excess burst.
>When Be = Bc in CAR, there is no burst. This is different from GTS and
>FRTS
>where the configured Be is above Bc. In CAR if you set Bc to 4000 and Be
>to
>8000, it means your excess burst is actually 4000.
>
>
>HTH,
>
>Brian McGahan, CCIE #8593
>bmcgahan@internetworkexpert.com
>
>Internetwork Expert, Inc.
>http://www.InternetworkExpert.com
>Toll Free: 877-224-8987 x 705
>Outside US: 775-826-4344 x 705
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > Yasser Aly
> > Sent: Tuesday, February 17, 2004 7:15 PM
> > To: ccie2b@hotmail.com; ccielab@groupstudy.com
> > Subject: RE: Limiting ICMP using CAR
> >
> > Hi Packet Man,
> >
> > Bc and Be are configured in Bytes not bits. I am not sure about
>whether
> > it
> > is per Tc or not.
> >
> > Needs clarification.
> >
> > Regards,
> > Yasser
> >
> > >From: "Packet Man" <ccie2b@hotmail.com>
> > >To: blackyeyes00@hotmail.com, ccielab@groupstudy.com
> > >Subject: RE: Limiting ICMP using CAR
> > >Date: Tue, 17 Feb 2004 18:27:11 -0500
> > >
> > >Yasser,
> > >
> > >I think the issue you might be having is due to the different units
>used
> > >for the different parameters. Remember that the 1st parameter, cir, is
> > in
> > >bits per SECONDS while the Bc and Be are in bits per Tc which is 1/8
>of
> > a
> > >second.
> > >
> > >So, 128,000 kbps dvided by 8 = 16,000 = bits per interval, Tc. To
>allow
> > >for a burst of 1/4 of this rate, divide by 4. 16,000 / 4 = 4000.
> > >
> > >Now, given the requirements you stated, I think the answer that was
> > >provided is wrong. I think it should be
> > > CIR Bc Be
> > >rate-limit output access-group 100 128000 16000 4000 conform-action
> > >transmit exceed-action drop
> > >
> > >Hopefully, if I'm mistaken, someone will immediately say so and point
>out
> > >my mistake. (It wouldn't be the 1st time)
> > >
> > >HTH
> > >
> > >
> > >>From: "Yasser Aly" <blackyeyes00@hotmail.com>
> > >>Reply-To: "Yasser Aly" <blackyeyes00@hotmail.com>
> > >>To: ccielab@groupstudy.com
> > >>Subject: Limiting ICMP using CAR
> > >>Date: Tue, 17 Feb 2004 18:07:34 -0500
> > >>
> > >>Hi group,
> > >>
> > >> The task is as follows: Configure E0/0 such that ICMP traffic is
> > limited
> > >>to 128Kbps.
> > >>Allow for a burst of 1/4th of this rate.
> > >>
> > >>
> > >>The answer for this question was as follows:
> > >>
> > >>acess-group 101 permit icmp any any
> > >>!
> > >>interface Ethernet0/0
> > >>rate-limit output access-group 100 128000 4000 4000 conform-action
> > >>transmit exceed-action drop
> > >>
> > >>I am confused why Bc and Be were set this way. Would you kindly
>explain
> > >>and give more detail on general concepts used when configuring Bc and
>Be
> > >>while using CAR.
> > >>
> > >>Regards,
> > >>Yasser
> > >>
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