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Chapter 18
SSO-BFD
The following line cards support the early packet send routine:
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To summarize the three modules, the sequence of steps before and after a switchover is as follows:
1.
2.
3.
4.
Note
Restrictions of SSO-BFD
The SSO-BFD feature has the following restrictions:
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OL-2226-23
1-port Channelized OC12 line card.
4-port channelized OC3/STM-1 line card.
Half-height Gigabit Ethernet line card.
Asynchronous Transfer Mode (ATM) line cards.
The BFD protocol checkpoint the sessions on the standby RP, and retain these sessions until the
sessions on the active RP are down or deleted. Checkpointing of sessions happen before the
switchover occurs. This is a continuous process each time a session comes up. The BFD protocol
registers with the enhanced timers infrastructure; the interval, at which the protocol is invoked by
the enhanced timers infrastructure, is specified depending on platform limitations.
When a planned or unplanned switchover event occurs, the standby RP is notified by the platform.
When the data plane on the standby RP is activated, it activates the enhanced timers infrastructure.
When the enhanced timers infrastructure is activated, the BFD process is invoked on the new active
RP. The BFD process goes through the queue of active sessions and sends packets using the early
packet send platform-specific path.
The enhanced timers infrastructure signals its registered client to send the next set of packets, at
regular intervals that is set earlier. This process continues until the control plane on the new active
RP is activated and the BFD protocol receives the RF_PROG_ACTIVE_FAST event. Once that
occurs, the BFD spawns its own pseudo preemptive process. The BFD protocol does not start the
detect timers and echo timers for sessions, when its starts receiving packets. If it has not received
packets from peer routers, the sessions begin to timeout.
The BFD control packets are sent when the platform starts receiving the BFD packets from peer
routers.
The timeout interval on PRE2 is slightly higher than PRE4 and PRE4, and can offset the utility of
BFD per session. The SSO-BFD feature is not supported on PRE2.
The Cisco 10000 series router needs about 1.6 seconds for packet express forwarder (PXF) to loop
the echo packets again after switchover.
In an non-Echo mode, when the ISSU is issued with minimum disruption, in about 700ms, the BFD
sessions resumes sending packets.
No error messages are displayed, if the user configures a timer lower than that can be supported for
the SSO-BFD feature in the Cisco 10000 series router.
If there is a link failure at the same time when a switchover occurs, there will be a delay in detecting
the forwarding failure on the local router that has just gone through a switchover. The platform
cannot receive packets during the delta time when the control plane has not come up.
When the BFD detection time is configured greater or equal to 5 seconds, the maximum number of
BFD HA sessions that the Cisco 10000 series router can support is 1100.
Cisco 10000 Series Router Software Configuration Guide
Restrictions of SSO-BFD
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Troubleshooting
