Configuring the BFD Protocol for RSVP-TE
The mpls rsvp bfd-liveness-detection command configures the Bidirectional Forwarding Detection (BFD) protocol for RSVP-TE. The BFD protocol uses control packets and shorter detection time limits to more rapidly detect failures in a network. Also, because they are adjustable, you can modify the BFD timers for more or less aggressive failure detection.
Without BFD, RSVP-TE can learn about adjacency failures by either of two methods. If RSVP-TE hellos are configured, then hello message timeouts indicate a failure. If hellos are not configured, then RSVP-TE learns about failures from resv and path messages.
When a BFD session exists between RSVP-TE peers, a peer that goes down is detected quickly, enabling faster rerouting of traffic. Adjacency failure detection by means of hello messages takes place on the order of seconds, whereas BFD fast failure detection can take place on the order of hundreds of milliseconds.
When you issue the mpls rsvp bfd-liveness-detection command on an RSVP-TE major interface, BFD liveness detection is established with all BFD-enabled RSVP-TE peers associated with that interface.
When an RSVP-TE session is established with the remote peer—if BFD is enabled and if the BFD session is not already present—then the local peer attempts to create a BFD session to the remote peer. The BFD session is established only if when both of the following are true:
- At least one RSVP-TE LSP exists between (passes through) a pair of directly connected RSVP-TE major interfaces.
- Both interfaces are BFD-enabled.
Consequently, when the last LSP is torn down between the interfaces, the BFD session is no longer required and is brought down as well.
Each adjacent pair of peers negotiates an acceptable transmit interval for BFD packets. The negotiated value can be different on each peer. Each peer then calculates a BFD liveness detection interval. When a peer does not receive a BFD packet within the detection interval, it declares the BFD session to be down and purges all routes learned from the remote peer.
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NOTE: Before the router can use the mpls rsvp bfd-liveness-detection command, you must specify a BFD license key. To view an already configured license, use the show license bfd command. |
For general information about configuring and monitoring the BFD protocol, see JUNOSe IP Services Configuration Guide, Chapter 5, Configuring BFD.
mpls rsvp bfd-liveness-detection
- Use to enable BFD (bidirectional forwarding detection) and define BFD values on an RSVP-TE major interface to more quickly detect RSVP-TE data path failures.
- The peers in an RSVP-TE adjacency use the configured values to negotiate the actual transmit intervals for BFD packets.
- You can use the the minimum-transmit-interval keyword to specify the interval at which the local peer proposes to transmit BFD control packets to the remote peer. Specify a number in the range 100–65535 milliseconds. The default value is 300 milliseconds.
- You can use the minimum-receive-interval keyword to specify the minimum interval at which the local peer must receive BFD control packets from the remote peer. Specify a number in the range 100–65535 milliseconds. The default value is 300 milliseconds.
- You can use the minimum-interval keyword to specify the same value for both of those intervals. Configuring a minimum interval has the same effect as configuring the minimum receive interval and the minimum transmit interval to the same value. Specify a number in the range 100–65535 milliseconds. The default value is 300 milliseconds.
- You can use the multiplier keyword to specify the detection multiplier value. The calculated BFD liveness detection interval can be different on each peer. The multiplier value is roughly equivalent to the number of packets that can be missed before the BFD session is declared to be down. Specify a number in the range 1–255. The default value is 3.
- By default, BFD is not configured or enabled on RSVP-TE major interfaces.
- For details on liveness detection negotiation, see Negotiation of the BFD Liveness Detection Interval section in JUNOSe IP Services Configuration Guide, Chapter 5, Configuring BFD.
- You can change the BFD liveness detection parameters at any time without stopping or restarting the existing session; BFD automatically adjusts to the new parameter value. However, no changes to BFD parameters take place until the values resynchronize with each peer.
- Example
host1(config-if)#mpls rsvp bfd-liveness-detection minimum-interval 400