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FTOS Configuration Guide for the C-Series - Force10 Networks

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Table 58 BFD Packet Fields<br />

Field Description<br />

Diagnostic Code The reason that <strong>the</strong> last session failed.<br />

State The current local session state. See BFD sessions.<br />

Flag A bit that indicates packet function. If <strong>the</strong> poll bit is set, <strong>the</strong> receiving system must<br />

respond as soon as possible, without regard to its transmit interval. The responding<br />

system clears <strong>the</strong> poll bit and sets <strong>the</strong> final bit in its response. The poll and final bits<br />

are used during <strong>the</strong> handshake and Demand mode (see BFD sessions).<br />

Note: <strong>FTOS</strong> does not currently support multi-point sessions, Demand mode,<br />

au<strong>the</strong>ntication, or control plane independence; <strong>the</strong>se bits are always clear.<br />

Detection Multiplier The number of packets that must be missed in order to declare a session down.<br />

Length The entire length of <strong>the</strong> BFD packet.<br />

My Discriminator A random number generated by <strong>the</strong> local system to identify <strong>the</strong> session.<br />

Your Discriminator A random number generated by <strong>the</strong> remote system to identify <strong>the</strong> session.<br />

Discriminator values are necessary to identify <strong>the</strong> session to which a control packet<br />

belongs since <strong>the</strong>re can be many sessions running on a single interface.<br />

Desired Min TX Interval The minimum rate at which <strong>the</strong> local system would like to send control packets to <strong>the</strong><br />

remote system.<br />

Required Min RX Interval The minimum rate at which <strong>the</strong> local system would like to receive control packets from<br />

<strong>the</strong> remote system.<br />

Required Min Echo RX The minimum rate at which <strong>the</strong> local system would like to receive echo packets.<br />

Note: <strong>FTOS</strong> does not currently support <strong>the</strong> echo function.<br />

Au<strong>the</strong>ntication Type<br />

An optional method <strong>for</strong> au<strong>the</strong>nticating control packets.<br />

Au<strong>the</strong>ntication Length<br />

Note: <strong>FTOS</strong> does not currently support <strong>the</strong> BFD au<strong>the</strong>ntication function.<br />

Au<strong>the</strong>ntication Data<br />

Two important parameters are calculated using <strong>the</strong> values contained in <strong>the</strong> control packet.<br />

• Transmit interval — Transmit interval is <strong>the</strong> agreed-upon rate at which a system sends control<br />

packets. Each system has its own transmit interval, which is <strong>the</strong> greater of <strong>the</strong> last received remote<br />

Desired TX Interval and <strong>the</strong> local Required Min RX Interval.<br />

• Detection time — Detection time is <strong>the</strong> amount of time that a system does not receive a control<br />

packet, after which <strong>the</strong> system determines that <strong>the</strong> session has failed. Each system has its own<br />

detection time.<br />

• In Asynchronous mode: Detection time is <strong>the</strong> remote Detection Multiplier multiplied by<br />

greater of <strong>the</strong> remote Desired TX Interval and <strong>the</strong> local Required Min RX Interval.<br />

• In Demand mode: Detection time is <strong>the</strong> local Detection Multiplier multiplied by <strong>the</strong> greater of<br />

<strong>the</strong> local Desired Min TX and <strong>the</strong> remote Required Min RX Interval.<br />

600 Bidirectional Forwarding Detection

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