Value,Description,Reference
0,Reserved,[RFC4666][RFC3868]
1,Registration Request (REG REQ),[RFC4666][RFC3868]
2,Registration Response (REG RSP),[RFC4666][RFC3868]
3,Deregistration Request (DEREG REQ),[RFC4666][RFC3868]
4,Deregistration Response (DEREG RSP),[RFC4666][RFC3868]
5-127,Unassigned,
128-255,Reserved for IETF-Defined RKM extensions,