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Enabling Distributed Periodic Packet Management

Periodic packet management (PPM) runs on the Routing Engine by default. You can now configure the router to run PPM on the Packet Forwarding Engine as well as on the Routing Engine. PPM is responsible for periodic transmission of packets on behalf of its various client processes, such as Bidirectional Forwarding Detection (BFD). PPM also receives packets on behalf of client processes. By default, PPM handles time-sensitive periodic processing and performs such processes as the gathering of statistics and the sending of process-specific packets. When you enable distributed PPM to run on the Packet Forwarding Engine, it continues to run on the Routing Engine as well. Distributing PPM to the Packet Forwarding Engine allows you to run such processes as BFD on the Packet Forwarding Engine. To enable distributed PPM, include the ppm statement:




ppm {
delegate-processing;
}

For a list of hierarchy levels at which you can configure this statement, see the statement summary section for this statement.

Note: Distributed PPM is supported only on the M120, M320, MX-series, T-series, and TX Matrix routing platforms.

The following types of sessions are not supported by distributed PPM:

Protocols other than BFD
Multihop BFD session
BFD session over a label-switched path
Any protocol session that does not explicitly specify that the adjacency and periodic sends must be distributed
Sessions over aggregated Ethernet interfaces and integrated routing and bridging interfaces

In addition, on the M120 routing platform, when Forwarding Engine Board (FEB) redundancy is configured and a FEB fails over, PPM sessions do not automatically switch over to the newly active FEB. For more information about FEB redundancy, see the JUNOS System Basics Configuration Guide.

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