how to work out the burst rate when policing on a switch

[carl_townshend]

Hi all

I hear there is a way to work out the correct burst rate when configuring policing on a switch, for example, if I wanted to police traffic to 10 Mbit on my switch, how do I work out the best burst rate to use ?

cheers

[Yogesh Ramdoss]

Carl,

Calculating the right burst size (Bc) is one of the hardest and time-consuming task.

Reasons: Calculating Bc involves several factors such as ingress/egress line rate, MTU and token bucket size, how fast the hardware sample the bucket etc.

Sample scenario:

For e.g., In Catalyst 6500 for CIR=100 Mbps and Tc = 0.25 msec

Bc = 100 * 10^6 * (1/8) * (0.25 * 10^-3) = 3125 bytes

(here 1/8 is to convert bits into bytes, as burst size is configured in bytes)

Burst size should be determined by trial-and-error method

.

Hope this helps

- Yogesh