small question about Token Bucket !!



is the Excessive Burst (Be) is the maximum capacity of the Token Bucket ?


also if the Bucket does not have enough tokens, will it wait to be fully filled in order to start servicing traffic?

or it can service with the amount it has (which is not full)?  


  • JoeMJoeM ✭✭✭

    Let's see if I can answer this as simple as possible, in average Joe language. ;-)  Definitely would like to read other short explanations.


    Excess Burst  (Be) is like a chance to regained earned credits.  If the CIRcuit has not been fullfilled completely for any intervals, then non-use credits are built up, and these lost opportunities can be filled with Be. can be used to burst past the CIR (with Bc + Be).   The idea is that the sum of the intervals will still come out to the CIR.  

    So, though intervals can be sent at a higher rate than the planned rate (Bc+Be) -- the total will still equal the CIR.

    Without ExcessBurst, the lost opportunities are not regained. 



    EDIT:  Here is another explanation by Paul Stewart on the Cisco forum. It is from 2009, but still relevant.

    example CIR (64Kbps)

                  intervals at 8000 bits (Bc) per .125 second (eight intervals per second)

                  Be = ???

    "...This is a difficult concept to grasp.  Sometimes, one person's way of
    explaining may make more sense to you than another's.  So if this is
    still confusing read plenty of examples and you'll get it..."

    Cisco Forum:   Difference between Normal and Excess Burst



  • EllieEllie ✭✭

    Thank you Joe for your explanations. That was one of my question as well. 

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