6.8.18. Holding Down Sessions

A system MAY choose to prevent a BFD session from being established. One possible reason might be to manage the rate at which sessions are established. This can be done by holding the session in Down or AdminDown state, as appropriate.

There are two related mechanisms that are available to help with this task. First, a system is REQUIRED to maintain session state (including timing parameters), even when a session is down, until a Detection Time has passed without the receipt of any BFD Control packets. This means that a system may take down a session and transmit an arbitrarily large value in the Required Min RX Interval field to control the rate at which it receives packets.

Additionally, a system MAY transmit a value of zero for Required Min RX Interval to indicate that the remote system should send no packets whatsoever.

So long as the local system continues to transmit BFD Control packets, the remote system is obligated to obey the value carried in Required Min RX Interval. If the remote system does not receive any BFD Control packets for a Detection Time, it SHOULD reset bfd.RemoteMinRxInterval to its initial value of 1 (per section 6.8.1, since it is no longer required to maintain previous session state) and then can transmit at its own rate.