Description

This KB introduces how to calculate burst duration from configured burst size of policer setting.

Symptoms

The burst size allows for short periods of traffic bursting in specific duration.
So if received burst packets in a short while, traffic will be dropped along with configured burst-size-limit.

Solution

You can calculate burst duration using the following method:
Burst duration = Burst-size-limit * 8 / Bandwidth-limit 

For example, when you have the config below, burst size will be 0.08 sec. 
set firewall policer Policer if-exceeding bandwidth-limit 1500000
set firewall policer Policer if-exceeding burst-size-limit 15k
set firewall policer Policer then discard
  • 15000 * 8 / 1500000  = 0.08
It indicates when receives 15 Kbytes in 80 msec, packets will be discarded.

Modification History

2023-08-29 : Created a KB

Related Information

burst-size-limit (Policer)