Administrator Guide

Field Description
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: The 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.
My Discriminator A random number generated by the local system to identify the session.
Your Discriminator A random number generated by the remote system to identify the session. Discriminator values are necessary to
identify the session to which a control packet belongs because there can be many sessions running on a single
interface.
Desired Min TX
Interval
The minimum rate at which the local system would like to send control packets to the remote system.
Required Min RX
Interval
The minimum rate at which the local system would like to receive control packets from the remote system.
Required Min Echo
RX
The minimum rate at which the local system would like to receive echo packets.
NOTE: The Dell Networking OS does not currently support the echo function.
Authentication Type,
Authentication
Length,
Authentication Data
An optional method for authenticating control packets.
NOTE: The Dell Networking OS does not currently support the BFD authentication function.
Two important parameters are calculated using the values contained in the control packet.
Transmit interval
Transmit interval is the agreed-upon rate at which a system sends control packets. Each system has its own
transmit interval, which is the greater of the last received remote Desired TX Interval and the local Required Min
RX Interval.
Detection time Detection time is the amount of time that a system does not receive a control packet, after which the system
determines that the session has failed. Each system has its own detection time.
• In Asynchronous mode: Detection time is the remote Detection Multiplier multiplied by greater of the remote
Desired TX Interval and the local Required Min RX Interval.
• In Demand mode: Detection time is the local Detection Multiplier multiplied by the greater of the local Desired
Min TX and the remote Required Min RX Interval.
BFD Sessions
You must enable BFD on both sides of a link in order to establish a session.
The two participating systems can assume either of two roles:
Active
The active system initiates the BFD session. Both systems can be active for the same session.
Bidirectional Forwarding Detection (BFD) 139