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Notable Replies

  1. Hi Rene,

    How actually we calculate the BC and BE base on the CIR. What is the standard we should set?

    Is the calculation below correct?

    CAR (Police) formula:
    Bc = CIR / 8 * Tc           (Default Tc = 1.5 seconds)
    Be = 2 * Bc


  2. Hi Davis,
    How Be is calculated depends on what type of policer is being used.

    Single Rate, Two Color Policer
    Bc = CIR/32
    Be = 0

    Single Rate, Three Color Policer
    Bc = CIR/32
    Be = Bc

    Two Rate, Three Color Policer
    Bc = CIR/32
    Be = PIR/32 (Peak Information Rate)
  3. Hi Andrew,

    Will there any different for the result if we set CIR/32 vs CIR/8 for the BE for the Single Rate, Three color policer?


  4. Hi Andrew,

    I still have some doubt

    Let say BC = the total token can be store, if let say the police cir 128kbps, and by default bc=cir/32 which is 4000 bytes.

    and every second refilled the token 128000/8 = 16000 bytes, but the BC is only can fill up max 4000 bytes?

    Then how the user can get 128kbps if the BC token(4000 bytes) is less than the CIR (16000 bytes)?


  5. Hello Rayniero

    In this case, there are two buckets. One is the BC bucket, which is the commited burst. This is traffic below and up to the CIR of the link. If this bucket is full at any given time, it overflows into the BE bucket, or the excess burst bucket. This has a specific size as well. The tokens are the actual data packets.

    In this example the buckets themselves are the maximum packets a link can support per time period. If the BC bucket is 128 kbps, that means 128000 bits in one second. If more than that arrive in one second, the excess goes into the BE bucket. If the BE bucket is 16 kbps, that means than an additional 16000 bits can be acomodated per second. If the BE bucket fills up too, then the additional packets are dropped.

    I hope this has been helpful!


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