2.3.2. Credit Window Association

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Original RFC Text

2.3.2.  Credit Window Association

   The Credit Window Association Data Item is used by a modem to
   associate traffic classification information with a destination.  The
   traffic classification information is identified using a TID value
   that has been previously sent by the modem or is listed in a Traffic
   Classification Data Item carried in the same message as the Credit
   Window Association Data Item.  TIDs in different credit windows must
   not overlap.

   A single Credit Window Association Data Item MUST be included in
   every Destination Up and Destination Update Message sent by a modem
   when a credit window flow control mechanism defined in this document
   is used.  Note that a TID will not be used unless it is listed in a
   Credit Window Association Data Item.

   The format of the Credit Window Association 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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Data Item Type                | Length (2)                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Traffic Class. Identifier (TID)|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Data Item Type:
      31

   Length:
      2

      As specified in [RFC8175], Length is the number of octets in the
      Data Item.  It MUST be equal to two (2).  If it is some other
      value, the Data Item is corrupt, so the message in which it
      appears cannot be reliably parsed and is ignored.

   Traffic Classification Identifier (TID):
      A 16-bit unsigned integer identifying a traffic classification set
      that has been identified in a Traffic Classification Data Item;
      see [RFC9892].

   A router that receives a Credit Window Association Data Item MUST
   locate the traffic classification information indicated by the
   received TID.  If no corresponding information is found, the Credit
   Window Association Data Item MUST be treated as an error as described
   above.  If the traffic classification information is located, the
   router MUST ensure that any data plane state that is associated with
   the TID and its corresponding FIDs is updated as needed (per
   Section 2.1).  If a router determines that a newly received Data Item
   results in credit windows with overlapping TIDs, the Data Item MUST
   be treated as an error as described above.