Bidirectional Forwarding Detection | 171
Figure 9-1. BFD in IPv4 Packet Format
Version
(4) IHL TOS Total Length Flags Frag Offset
Source Port Destination Port Length BFD Control Packet
Header
Checksum Src IP Addr
TTL
(255) Protocol Dest IP Addr Options Padding
Preamble Start Frame
Delimiter Destination MAC Source MAC Ethernet Type
(0x8800) IP Packet Padding FCS
UDP Packet
Checksum
Range: 3784Range: 3784
Random number generated by
the local system to identify
a session
Random number generated by
the local system to identify
a session
The minimum interval between
Echo packtes that the local system
is capable of supporting
The minimum interval between
Echo packtes that the local system
is capable of supporting
The number of packets that
must be missed in a row in
order to declare a session down
The number of packets that
must be missed in a row in
order to declare a session down
The minimum interval between
control packets that the local
system is capable of supporting
The minimum interval between
control packets that the local
system is capable of supporting
Random number generated by
remote system to identify a
session
Random number generated by
remote system to identify a
session
The intervals at which the local
system would like to transmit
control packets
The intervals at which the local
system would like to transmit
control packets
Version
(1) Diag Code State Detect Mult Length My
Discriminator Required
Min RX Interval Required Min
Echo RX Interval
Your
Discriminator Desired
Min TX Interval Auth Type Auth Length Auth Data
Range: 0-31
Code: 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
Range: 0-31
Code: 0: AdminDown
1: Down
2: Init
3: Up
Flags
Bit: P: Poll
F: Final
C: Control Plane Independent
A: Authentication Present
D: Demand
(Final bit reserved)
Range: 3784
Echo: 3785
Range: 3784
Echo: 3785