4.1. LOWPAN_NHC Format

Compression formats for different next headers are identified by a variable-length bit-pattern immediately following the LOWPAN_IPHC compressed header. When defining a next header compression format, the number of bits used SHOULD be determined by the perceived frequency of using that format. However, the number of bits and any remaining encoding bits SHOULD respect octet alignment. The following bits are specific to the next header compression format. This document defines a compression format for IPv6 Extension and UDP headers.

            +----------------+---------------------------
            | var-len NHC ID | compressed next header...
            +----------------+---------------------------

                   Figure 12: LOWPAN_NHC Encoding