Value,Description,Reference
1,IPv4 prefix,[RFC3209]
2,IPv6 prefix,[RFC3209]
3,Unassigned,
4,Unnumbered Interface ID,[RFC3477]
5,4-byte AS number,[RFC7897][RFC7898]
6,OSPF Area ID,[RFC7897][RFC7898]
7,IS-IS Area ID,[RFC7897][RFC7898]
8,Optical Interface Class List,[RFC8780]
9,Client Signal Information,[RFC8780]
10,Label,[RFC8779]
11,LSP,[RFC9504]
12-31,Unassigned,
32,Autonomous system number,[RFC3209]
33,Unassigned,
34,SRLG,[RFC4874]
35-63,Unassigned,
64,IPv4 Path Key,[RFC5520]
65,IPv6 Path Key,[RFC5520]
66-127,Unassigned,