Burst field while policing traffic

[min.chen]

Hello,

Can someone explain the burst field in policing traffic on a 4k switch a little bit better than the Cisco's QoS documentations?

For example If I want to police a 100 meg fastethernet port down to only allow 1 meg of traffic, I can use the following config in conjunction with other QOS commands.

police 1 mbps 128 kbyte conform-action transmit exceed-action drop

However, my biggest question is, how do I determine the value for the second field? (in the example above it is 128kbyte)

I have been playing with values in the lab and I find that if I make the burst too small I can't get any traffic across. I am currently setting the burst to about 10% of the set bandwidth. It seems to be ok, but I would like a little bit more explaination on what exactly is going on. Thanks for everyone's help.

Thanks

Min

[wong34539]

A good value for burst can be equal to twice the amount of traffic sent with Round trip time.

= 2* *

You can get better undersatnding from the below link too

http://www.cisco.com/en/US/products/hw/switches/ps663/products_tech_note09186a00800946e9.shtml#topic1

[min.chen]

Burst = 2 * .001 * 1000000 = 2000

police 1mbps 2kbyte conform-action transmit exceed-action drop

If I put 2k for burst FTP will never work.

Why??