Anyone know how to use Commited Access Rate?

[rtdoran]

Can I use CAR (commited access rate) and an A.C.L. to limit the bandwidth used by IP address through an ethernet interface? I am using a Cisco 2600

 

[omartin]

Yes you can ! You need the version that supports it, and it's the IP only software. Then create the access-list you want your router to limit traffic on, and apply the CAR statement to the interface on which traffic will arrive.

int eth0
ip rate-limit group <acl-number> ....


Olivier Martin
--------------
Read that somewhere and I think its cool :
If you want to accelerate a Windoze Box, there is an easy way to have it accelerate at -9.8 m/s^2

 

[omartin]

I checked and here is the interface command to use :

rate-limit input access-group <xxx> <burst-normal> <burst-max> conform-action <transmit,drop - why would you want to drop it anyways > exceed action <mark,drop...>


Good luck ! Olivier Martin
--------------
Read that somewhere and I think its cool :
If you want to accelerate a Windoze Box, there is an easy way to have it accelerate at -9.8 m/s^2

 

[rtdoran]

Thanks for the reply,
How do I set what I want the bandwidth limit to be set at?

 

[omartin]

For example :

rate-limit input access-group 120 5000000 24000 24000 conform-action
transmit exceed-action drop

Would set a limit of 5Mbps for the traffic on access-list 120. The 24000 is for the amount of bytes in the token bucket, which I suggest you read about on cisco's web site. Basically, it's a concept in which this is the depth of the buffer sending packets. This buffer empties at 5Mbps but has 24KBytes capacity (without at first considering the excess buffer capacity, the other 24000 argument). That is, if your workstation sends instantly (which is not possible, but supposed it was) 24000 bytes, this would yeild an infinite bandwidth (which could top at 1 Gbps in a gigabit network) to the router, without having any traffic dropped, as long as it stops right after for the time to empty the token bucket (divide 24000 BYTES/5Mbits per seconds = 0,0384 seconds). So every 0,0384 seconds, you can send 24000 bytes without overpassing the bandwidth you set on the router. You have at LEAST to put 1500 Bytes in this bucket because if your packets are full ethernet sized and the bucket does not have enough space in it, it will discard the packet. In UDP traffic, this is pretty bad, as opposed to TCP which can survive traffic drops.

Hope this helps ...
Olivier
Olivier Martin
--------------
Read that somewhere and I think its cool :
If you want to accelerate a Windoze Box, there is an easy way to have it accelerate at -9.8 m/s^2