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Forum Replies

  1. Hi Hamood,

    Glad to hear it was useful!


  2. Hi Abhishek,

    There are four classes: 1, 2, 3 and 4. The higher the class number, the higher the priority. Class 4 has a higher priority (value) than any of the other classes.

    Within each class, there is a low, medium and high drop probability.

    These values are described in the RFC. In reality, they are just markings and it’s up to you to configure your routers/switches to act upon these different markings.


  3. Hi Ajay,

    The two CU bits are currently unused and ignored.

    When you look at AF, the first three bits are the class and the 4th + 5th bit are the drop probability. You can ignore the 6th bit.

    AF31 = 011 010

    011 = 3
    01 = 1

    That’s why AF31 is 26 in decimal.


    *Edit* A previous typo of “110” was corrected to “011”

  4. The text below has also to be corrected.

    _> The first 3 bits are used to define the class and the next 3 bits are used to define the drop probability. Here are all the possible values that we can use:_

    Only 2 bits are used for drop probability, the 6th bit is ignored.

  5. Hello Maodo

    According to RFC2474 it speaks about the DS field:

       Implementors should note that the DSCP field is six bits wide.  DS-
       compliant nodes MUST select PHBs by matching against the entire 6-bit
       DSCP field, e.g., by treating the value of the field as a table index
       which is used to select a particular packet handling mechanism which
       has been implemented in that device.  The value of the CU field MUST
       be ignored by PHB selection.  

    It says that the entire 6-bit field must be used. The bits in question are bits 0 to 5 (a total of six bits

    ... Continue reading in our forum

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