5. IANA Considerations

This document defines a new IPv6 header compression format for 6LoWPAN. The document allocates the following 32 Dispatch type field values for LOWPAN_IPHC:

  01 100000
   through
  01 111111

This assignment preempts the assignment of 01 111111 for ESC [RFC4944]; this preemption is possible because extension bytes that would enable the use of ESC have not been allocated yet. Instead, the value:

  01 000000

is reserved as a replacement value for ESC, to be finally assigned with the first assignment of extension bytes.

This document also creates a new IANA registry for the LOWPAN_NHC header type, with the following initial content:

  00000000 to 11011111: (unassigned)
  1110000N: IPv6 Hop-by-Hop Options Header       [RFC6282]
  1110001N: IPv6 Routing Header                  [RFC6282]
  1110010N: IPv6 Fragment Header                 [RFC6282]
  1110011N: IPv6 Destination Options Header      [RFC6282]
  1110100N: IPv6 Mobility Header                 [RFC6282]
  1110111N: IPv6 Header                          [RFC6282]
  11110CPP: UDP Header                           [RFC6282]
  11111000 to 11111110: (unassigned)

Capital letters in bit positions represent class-specific bit assignments. N indicates whether or not additional LOWPAN_NHC encodings follow, as defined in Section 4.2. CPP represents variables specific to UDP header compression defined in Section 4.3.

The policy for this registry [RFC5226] is IETF Review. In this process, new values SHOULD be assigned in a way that preserves the NHC ID abstraction of Section 4 (i.e., k one-bits followed by one zero-bit identify the general class of NHC, followed by class-specific bit assignments).