H3C Technologies H3C S12500 Series Switches - Manual (Page 206)

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Figure 49 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 19 lists the states.
Table 19 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, and is expecting a packet with the Final (F) bit in reply. 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.
• Control Plane Independent(C)—If set, the transmitting system's BFD implementation does not share
fate with its control plane (in other words, BFD is implemented in the forwarding plane and can
continue to function through disruptions in the control plane.) If clear, the transmitting system's BFD
implementation shares fate with its control plane.
• Authentication Present (A)—If set, the Authentication Section is present and the session is to be
authenticated.
• Demand (D—If set, Demand mode is active in the transmitting system. (The system wishes to operate
in Demand mode, knows that the session is up in both directions, and is directing the remote system