The ROHC suboption identifier is a non-negative integer.
The IANA policy for assigning new values for the suboption
identifier shall be Specification Required: values and their
meanings must be documented in an RFC or in some other permanent
and readily available reference, in sufficient detail that
interoperability between independent implementations is possible.
The range 0 to 127 is reserved for IETF standard-track
specifications; the range 128 to 254 is available for other
specifications that meet this requirement (such as Informational
RFCs). The value 255 is reserved for future extensibility of the