2.2. Diffserv Traffic Classification Sub-Data Item

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Original RFC Text

2.2.  Diffserv Traffic Classification Sub-Data Item

   The Diffserv Traffic Classification Sub-Data Item identifies the set
   of DSCPs that should be treated as a single flow, i.e., receive the
   same traffic treatment.  DSCPs are identified in a list of Diffserv
   fields.  An implementation that does not support DSCPs and wants the
   same traffic treatment for all traffic to a destination or
   destinations would indicate 0 DSCPs.

   The format of the Diffserv Traffic Classification Sub-Data Item is as
   follows:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Sub-Data Item Type (1)        |  Length                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Flow Identifier (FID)         |   Num DSCPs   |   DS Field 1  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   DS Field 2  |      ...      |   DS Field n  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sub-Data Item Type:
      Sub-Data Item Type with value one (1) identifies the Diffserv
      Traffic Classification Sub-Data Item Type in the format defined in
      Section 2.1.1.

   Length:
      Variable

      Length is defined above.  For this Sub-Data Item, it is equal to
      three (3) octets plus the value of the Num DSCPs field.  This
      means that the maximum Length value is 3 + 64 or 67 octets.  The
      definition can be in multiple Sub-Data Items that are much smaller
      than this.

   Flow Identifier (FID):
      A 16-bit unsigned integer representing the data plane information
      carried in the Sub-Data Item that is to be used in identifying a
      flow.  The value 0xFFFF is reserved and MUST NOT be used in this
      field.

   Num DSCPs:
      An 8-bit unsigned integer indicating the number of DSCPs carried
      in the Sub-Data Item.  A zero (0) indicates a (wildcard) match
      against any DSCP value that does not have an explicit match to a
      FID.  A typical use of this is mapping any DSCPs that are not
      explicitly mapped to a default queue.

   DS Field:
      Each DS Field is 8 bits long and carries the DSCP field as defined
      in [RFC2474].

                  0   1   2   3   4   5   6   7
                +---+---+---+---+---+---+---+---+
                |         DSCP          |  MBZ  |
                +---+---+---+---+---+---+---+---+

      DSCP:  Differentiated Services Code Point [RFC2474]
      MBZ:  Must Be Zero - set to zero when transmitted