Dell Force10 Z9000 Configuration Manual page 126

Table 7-1. BFD Packet Fields
Field
Diagnostic Code
State
Flag
Detection Multiplier
Length
My Discriminator
Your Discriminator
Desired Min TX Interval
Required Min RX Interval
Required Min Echo RX
Authentication Type
Authentication Length
Authentication Data
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
BFD must be enabled on both sides of a link in order to establish a session. The two participating systems
can assume either of two roles:
| Bidirectional Forwarding Detection (BFD)
126
Description
The reason that the last session failed.
The current local session state. See
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 final bit in its response. The poll and final bits are used during the handshake
and Demand mode (see BFD
Note: FTOS does not currently support multi-point sessions, Demand mode, authentication, or
control plane independence; these bits are always clear.
The number of packets that must be missed in order to declare a session down.
The entire length of the BFD packet.
A random number generated by the local system to identify the session.
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 since there can
be many sessions running on a single interface.
The minimum rate at which the local system would like to send control packets to the remote
system.
The minimum rate at which the local system would like to receive control packets from the
remote system.
The minimum rate at which the local system would like to receive echo packets.
Note: FTOS does not currently support the echo function.
An optional method for authenticating control packets.
Note: FTOS does not currently support the BFD authentication function.
BFD sessions.
sessions).