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Forum Replies

  1. Hi Davis,

    It depends what you want to achieve.

    For example, the ISP will probably use policing since they don’t want to waste resources to buffer customer packets exceeding traffic.

    The customer however probably doesn’t want packet drops so they will configure shaping to match the rate that the ISP polices at.

    Also keep in mind that shaping adds delay so it’s not a good idea to use this for realtime traffic like VoIP.


  2. Hi Muhammad,

    Policing is typically implemented by ISPs to limit the traffic of their customers so it will depend on the traffic contract that they sell you.

    The single rate two color policer might be a bit unfair since it doesn’t allow bursting. With a CIR of 128kbps then you’ll only be able to reach 128kbps if you keep sending traffic non-stop.

    The single rate three color policer allows bursting. Since data traffic is “bursty” by nature, this is probably a bit more fair to use. When your connection is idle, you can accumulate up to the Be and spend your Bc+Be

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  3. Hi Rawa,

    I answered the first question a bit above this post.

    Here’s a configuration example for all types btw:

    Policing Configuration Example

    The dual-rate three-color policer will always check both buckets. It will try to take tokens from both buckets, if possible then the traffic is conforming. If the BC bucket is empty but the PIR bucket still has tokens then the traffic is exceeding. Keep in mind the PIR bucket is larger than the BC bucket.


  4. Hi Chris,

    With a policer, each token represents a single byte so that’s how you know the size of the bucket. When you police at 128000 bps, that’s a bucket that can store 128000 / 8 = 16000 bytes.


  5. Hello,

    Just a small comment.
    The formulas:
    Packet arrival time - Previous packet arrival time * Police Rate / 8
    should be replaced with:
    (Packet arrival time - Previous packet arrival time) * Police Rate / 8

    Thank you,

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