Configuring Bfd - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - IP SERVICES CONFIGURATION GUIDE 2010-10-01 Configuration Manual

Software for e series broadband services routers ip services configuration guide
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Copyright © 2010, Juniper Networks, Inc.
The negotiated transmit interval for a peer is the interval between the BFD packets that
it sends to its peers. The receive interval for a peer is the minimum time that it requires
between packets sent from its peer; the receive interval is not negotiated between peers.
To determine the transmit interval, each peer compares its configured minimum transmit
interval with its peer's minimum receive interval. The larger of the two numbers is accepted
as the transmit interval for that peer.
Consider the following example. Router A and Router B are peers, with the following BFD
liveness detection values configured.
Configured Transmit
Router
Interval (ms)
A
400
B
450
For Router A, the negotiated transmit interval is the greater of its transmit interval (400
ms) and the Router B receive interval (450 ms), or 450 ms.
For Router B, the negotiated transmit interval is the greater of its transmit interval (450
ms) and the Router A receive interval (500 ms), or 500 ms.
The liveness detection interval is the period a peer waits for a BFD packet from its peer
before declaring the BFD session to be down. The detection interval is determined
independently by each peer and can be different for each. The detection interval for the
local peer is calculated as the remote peer's negotiated transmit interval times the
detection multiplier value configured on the remote peer.
Negotiated
Transmit Interval
Router
(ms)
A
450
B
500
For Router A, the detection interval is Router B's negotiated transmit interval times the
Router B detection multiplier: 500 ms x 3 = 1500 ms.
For Router B, the detection interval is Router A's negotiated transmit interval times the
Router A detection multiplier: 450 ms x 2 = 900 ms.
If Router A fails to receive a BFD packet from Router B within 1500 milliseconds, Router
A declares the BFD session to be down. Similarly, if Router B fails to receive a BFD packet
from Router A within 900 milliseconds, Router B declares the BFD session to be down.
In either case, all routes learned from the failed peer are purged immediately.
Chapter 4: Configuring BFD
Configured Receive
Interval (ms)
500
450
Detection
Liveness Detection
Multiplier
Interval (ms)
2
1500
3
900
109

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