Cisco NCS 6000 Series Configuration Manual page 156

Echo Packet Latency
The BFD control packet failure detection time is the maximum amount of time that can elapse without receipt
of a BFD control packet before the BFD session is declared down.
• Value of (I x M) x M—BFD echo packet failure detection time. This is the maximum amount of time
Table 4: BFD Packet Intervals and Failure Detection Time Examples on Bundle Interfaces
Configured Async
Control Packet
Interval (ms)
(bfd address-family
ipv4
minimum-interval)
33
50
75
200
2000
15000
1
Echo Packet Latency
BFD only detects an absence of receipt of echo packets, not a specific delay for TX/RX of a particular echo
packet. In some cases, receipt of BFD echo packets in general can be within their overall tolerances for failure
detection and packet transmission, but a longer delay might develop over a period of time for any particular
roundtrip of an echo packet (See
You can configure the router to detect the actual latency between transmitted and received echo packets on
non-bundle interfaces and also take down the session when the latency exceeds configured thresholds for that
roundtrip latency. For more information, see the
Detection.
In addition, you can verify that the echo packet path is within specified latency tolerances before starting a
BFD session. With echo startup validation, an echo packet is periodically transmitted on the link while it is
down to verify successful transmission within the configured latency before allowing the BFD session to
change state. For more information, see the
and Latency.
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
134
• Minimum period between sending of BFD echo packets.
that can elapse without receipt of a BFD echo packet (using the standard multiplier counter scheme as
described in Echo Packet Failure Detection In Asynchronous
down.
Configured
Multiplier
(bfd address-family
ipv4 multiplier)
3
3
4
2
3
3
The maximum echo packet interval for BFD on bundle member links is the minimum of either 30
seconds or the asynchronous control packet failure detection time.
Async Control
Packet Failure
Detection Time
(ms)
(Interval x
Multiplier)
99
150
300
400
6000
45000
Example 3).
Configuring BFD Session Teardown Based on Echo Latency
Delaying BFD Session Startup Until Verification of Echo Path
Implementing BFD
Mode) before the BFD session is declared
Echo Packet Interval Echo Packet Failure
Detection Time
(Async Control
Packet Failure (Echo Interval x
Detection Time) Multiplier)
99 297
150 450
300 1200
400 800
6000 18000
1
30000 90000