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Configuring IP Router Parameters
Page 34 7750 SR OS Router Configuration Guide
If multiple BFD sessions exist between two nodes, the BFD discriminator is used to de-multiplex
the BFD control packet to the appropriate BFD session.
Control Packet Format
The BFD control packet has 2 sections, a mandatory section and an optional authentication section.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Vers | Diag |Sta|P|F|C|A|D|R| Detect Mult | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Your Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Desired Min TX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Required Min Echo RX Interval |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Mandatory Frame Format
Table 3: BFD Control Packet Field Descriptions
Field Description
Vers The version number of the protocol. The initial protocol version is 0.
Diag A diagnostic code specifying the local system’s reason for the last transition of the
session from Up to some other state.
Possible values are:
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
H Bit The “I Hear You” bit. This bit is set to 0 if the transmitting system either is not
receiving BFD packets from the remote system, or is in the process of tearing down
the BFD session for some reason. Otherwise, during normal operation, it is set to 1.