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10. BGP Timers

  1. BGP Timers

BGP employs five timers: ConnectRetryTimer (see Section 8), HoldTimer (see Section 4.2), KeepaliveTimer (see Section 8), MinASOriginationIntervalTimer (see Section 9.2.1.2), and MinRouteAdvertisementIntervalTimer (see Section 9.2.1.1).

Two optional timers MAY be supported: DelayOpenTimer, IdleHoldTimer by BGP (see Section 8). Section 8 describes their use. The full operation of these optional timers is outside the scope of this document.

ConnectRetryTime is a mandatory FSM attribute that stores the initial value for the ConnectRetryTimer. The suggested default value for the ConnectRetryTime is 120 seconds.

HoldTime is a mandatory FSM attribute that stores the initial value for the HoldTimer. The suggested default value for the HoldTime is 90 seconds.

During some portions of the state machine (see Section 8), the HoldTimer is set to a large value. The suggested default for this large value is 4 minutes.

The KeepaliveTime is a mandatory FSM attribute that stores the initial value for the KeepaliveTimer. The suggested default value for the KeepaliveTime is 1/3 of the HoldTime.

The suggested default value for the MinASOriginationIntervalTimer is 15 seconds.

The suggested default value for the MinRouteAdvertisementIntervalTimer on EBGP connections is 30 seconds.

The suggested default value for the MinRouteAdvertisementIntervalTimer on IBGP connections is 5 seconds.

An implementation of BGP MUST allow the HoldTimer to be configurable on a per-peer basis, and MAY allow the other timers to be configurable.

To minimize the likelihood that the distribution of BGP messages by a given BGP speaker will contain peaks, jitter SHOULD be applied to the timers associated with MinASOriginationIntervalTimer, KeepaliveTimer, MinRouteAdvertisementIntervalTimer, and ConnectRetryTimer. A given BGP speaker MAY apply the same jitter to each of these quantities, regardless of the destinations to which the updates are being sent; that is, jitter need not be configured on a per-peer basis.

RFC 4271 BGP-4 January 2006

The suggested default amount of jitter SHALL be determined by multiplying the base value of the appropriate timer by a random factor, which is uniformly distributed in the range from 0.75 to 1.0. A new random value SHOULD be picked each time the timer is set. The range of the jitter's random value MAY be configurable.

RFC 4271 BGP-4 January 2006

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