H3C Technologies H3C MSR 50 - Manual (Page 15)

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• SHA1—SHA1 (Secure Hash Algorithm 1) authentication.
BFD packet format
BFD control packets are encapsulated into UDP packets with port number 3784 for single-hop detection
or port number 4784 for multi-hop detection (also can be 3784 based on the configuration task). BFD
echo packets have a similar format as BFD control packets with UDP port number 3785 except that the
Desired Min TX Interval and Required Min RX Interval fields are null. Figure 3 illustrates the packet format.
Figure 3 BFD packet format
• Vers—Protocol version. The protocol version is 1.
• Diag—This bit indicates the reason for the last transition of the local session from up to some other
state.
Table 4 lists the states.
Table 4 Diag bit values
Diag Description
0 No Diagnostic.
1 Control Detection Time Expired.
2 Echo Function Failed.
3 Neighbor Signaled Session Down.
4 Forwarding Plane Reset.
5 Path Down.
6 Concatenated Path Down.
7 Administratively Down.
8 Reverse Concatenated Path Down.
9–31 Reserved for future use.
• State (Sta)—Current BFD session state. Its value can be 0 for AdminDown, 1 for Down, 2 for Init,
and 3 for Up.
• Poll (P)—If set, the transmitting system is requesting verification of connectivity, or of a parameter
change. If clear, the transmitting system is not requesting verification.
• Final (F)—If set, the transmitting system is responding to a received BFD control packet that had the
Poll (P) bit set. If clear, the transmitting system is not responding to a Poll.