bandwidth command with police

[uthayaman]

We have 2Mbps links at hub and 6 branch locations each with 512 kbps in a mpls cloud.We have applied QOS at hub(Outward) to rate limit one of the application which will consume more bandwidth.We decided to allow up to 250 kbps for this particular application and rest can be used for other.We are applying it with the help of police function.

All the branches will not access the application at the same time so my hub location bandwidth will not go beyond 2Mbps.

If i didnt apply police at hub, branch link is mostly utlized by this application.Hence we have controlled this at hub location by rate limiting the download traffic.

Now my question is do i need to apply bandwidth command at hub location.What is the effect of having bandwidth command in WAN interface of my hub location when we use police.

[Lei Tian]

Hi,

Policer is not a queueing mechanism, it doesn't aware the link congestion status. It just simply rate limit traffic to a configured rate. Bandwidth is a queueing mechanism, it only kicks in when there is congestion on the link.

So if you want to guarantee certain bandwidth for this class during congestion, and make sure this class never exceed a specific rate; you can use both police and bandwidth under same class. Theoretically it should work, but you should test it first since qos works differently on platform and IOS version.

HTH,

Lei Tian