Value,Description,Reference
0,(reserved),
1,(SCCRQ) Start-Control-Connection-Request,
2,(SCCRP) Start-Control-Connection-Reply,
3,(SCCCN) Start-Control-Connection-Connected,
4,(StopCCN) Stop-Control-Connection-Notification,
5,(reserved),
6,(HELLO) Hello,
20,(ACK) Explicit Acknowledgement,[RFC3931]