Common Interval Support in Bidirectional Forwarding Detection

This RFC 7419 was published in 2014.


Bidirectional Forwarding Detection (BFD) requires that messages be transmitted at regular intervals and provides a way to negotiate the interval used by BFD peers.
Some BFD implementations may be restricted to only support several interval values.
When such BFD implementations speak to each other, there is a possibility of two sides not being able to find a common value for the interval to run BFD sessions.

RFC 7419 introduction

The Bidirectional Forwarding Detection (BFD) standard [RFC5880] describes how to calculate the transmission interval and the detection time.
However, it does not make any statement about how to solve a situation where one BFD speaker cannot support the calculated value.
In practice, this may not have been a problem as long as software-implemented timers were used and as long as the granularity of such timers was small compared to the interval values being supported, i.e.
as long as the error in the timer interval was small compared to 25 percent jitter.

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