Value,Description,Reference,Notes
0,Invalid,,
1,Request,[RFC1058],
2,Response,[RFC1058],
3,TraceOn,[RFC1058],
4,TraceOff,[RFC1058],
5,Reserved,[RFC1058],
6,Triggered Request,[RFC1582],"There are widely deployed implementations that don't support Triggered UDP that use value 6 = ""Poll Entry"" (undocumented)"
7,Triggered Response,[RFC1582],
8,Triggered Acknowledgement,[RFC1582],
9,Update Request,[RFC2091],
10,Update Response,[RFC2091],
11,Update Acknowledge,[RFC2091],
12-254,Unassigned,,