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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 interv
als at which th
e local
system would like to tran
smit
con
trol pack
ets
The interv
als at which th
e local
system would like to tran
smit
con
trol pack
ets
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