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2.3. Ethernet Traffic Classification Sub-Data Item

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Original RFC Text​

2.3.  Ethernet Traffic Classification Sub-Data Item

   The Ethernet Traffic Classification Sub-Data Item identifies the VLAN
   and PCPs that should be treated as a single flow, i.e., receive the
   same traffic treatment.  Ethernet PCP support is defined as part of
   the IEEE 802.1Q tag format [IEEE8021Q] and includes a 3-bit "PCP"
   field.  The tag format also includes a 12-bit "VLAN Identifier (VID)"
   field.  PCPs are identified in a list of Priority Fields.  An
   implementation that does not support PCPs and wants the same traffic
   treatment for all traffic to a destination or destinations would
   indicate 0 PCPs.  Such an implementation could identify a VLAN to use
   per destination.

   The format of the Ethernet 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 (2)        | Length                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Flow Identifier (FID)         |NumPCPs| VLAN Identifier (VID) |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Pri. 1| Pri. 2| ..... | ..... | ..... |  Pad  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Sub-Data Item Type:
      Sub-Data Item Type with value two (2) identifies the Ethernet
      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
      four (4) plus the number of octets needed to accommodate the
      number of Priority Fields indicated by the NumPCPs field.  Note
      that as the length is in octets and each Priority Field is 4 bits,
      the total length of this Sub-Data Item is the 2 octets of Flow
      Identifier, plus the 2 octets for NumPCPs and VLAN Identifier plus
      the number of octets for PCPs.  The number of octets for the PCPs
      is computed by rounding up NumPCPs to the nearest even value and
      dividing by 2.  This TLV has maximum length of 4 plus 8 divided by
      2 or 8 octets.

   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.

   NumPCPs:
      A 4-bit unsigned integer indicating the number of Priority Fields
      carried in the Sub-Data Item.  A zero (0) indicates a (wildcard)
      match against any PCP value that does not have an explicit match
      to a FID.  A typical use of a wildcard is mapping any PCPs that
      are not explicitly mapped to a default queue.  The maximum number
      of PCPs is 8.

   VLAN Identifier (VID):
      A 12-bit unsigned integer field indicating the VLAN to be used in
      traffic classification.  VID value zero (0x000) is used to
      indicate that the VID is to be ignored.  VID 0xFFF is reserved.
      Any other VID value from 0x001 through 0xFFE can be used in
      traffic classification.  Any explicitly mapped VLANs are matched
      first.  Any VLANs that do not have a mapping will then map to this
      default mapping.

   Priority:
      Each Priority Field is 4 bits long and indicates a PCP field as
      defined in [IEEE8021Q].  Note that zero (0) is a valid value for
      PCP.

                0   1   2   3
              +---+---+---+---+
              |    PCP    |MBZ|
              +---+---+---+---+

      PCP:  Priority Code Point [IEEE8021Q]
      MBZ:  Must Be Zero - set to zero when transmitted

   Pad:
      A field that is 4 bits long and is included when NumPCPs is an odd
      number.  This field MUST be set to zero by the sender and MUST be
      ignored on receipt.
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