Bfd packet format – H3C Technologies H3C MSR 50 User Manual
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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.
illustrates the packet format.
Figure 3 BFD packet format
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Vers—Protocol version. The protocol version is 1.
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Diag—This bit indicates the reason for the last transition of the local session from up to some other
state.
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.
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State (Sta)—Current BFD session state. Its value can be 0 for AdminDown, 1 for Down, 2 for Init,
and 3 for Up.
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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.
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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.