Token bucket for policer and shaper.

Hi All ,

I am facing lot of issues to understand the token bucket algoritham for shaping and policing .

I understood the following thing.

Bc is the token bucket size and every Tc interval token equal to Bc will be added to the bucket .if that will overflow the bucket then rest of the token will be discarded .If a particular Tc interval no packet is flowing through the bucket means that token will get added to the next Tc interval.

Please correct me if iam wrong . Then what is the need for a Be value in police command

Please explain the concept of  token bucket for both policer and shaper.

thanks in advance

Arun