Service Manual

BFD Packet Format
Control packets are encapsulated in user datagram protocol (UDP) packets. The following illustration shows the complete
encapsulation of a BFD control packet inside an IPv4 packet.
Figure 12. BFD in IPv4 Packet Format
Field
Description
Diagnostic Code The reason that the last session failed.
State The current local session state. Refer to BFD Sessions.
Flag A bit that indicates packet function. If the poll bit is set, the receiving system must respond as soon as
possible, without regard to its transmit interval. The responding system clears the poll bit and sets the nal
bit in its response. The poll and nal bits are used during the handshake and in Demand mode (refer to BFD
Sessions).
NOTE: Dell Networking OS does not currently support multi-point sessions, Demand mode,
authentication, or control plane independence; these bits are always clear.
Detection Multiplier The number of packets that must be missed in order to declare a session down.
Length The entire length of the BFD packet.
Bidirectional Forwarding Detection (BFD)
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