Intersection algorithm: Difference between revisions

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{{short description|Algorithm for selecting the best sources for time estimation}}

The '''intersection algorithm''' is an agreement algorithm used to select sources for estimating accurate time from a number of [[noise|noisy]] time sources. It forms part of the modern [[Network Time Protocol]]. It is a modified form of [['''Marzullo's algorithm]]'''.<ref name=":0">{{cite web |url= http://tools.ietf.org/html/rfc1305#ref-DEC89 |title=RFC 1305 - Network Time Protocol (Version 3) Specification, Implementation and Analysis |first= |last= |work=tools.ietf.org |year=2013 |quote=Digital Time Service Functional Specification Version T.1.0.5. Digital Equipment Corporation, 1989. |accessdate=October 6, 2013}}</ref><ref>Digital Time Service Functional Specification Version T.1.0.5. Digital

Equipment Corporation, 1989.</ref>

While Marzullo's algorithm will return the smallest interval consistent with the largest number of sources, the <ref name=":0" />returned interval does not necessarily include the center point (calculated offset) of all the sources in the intersection. The intersection algorithm returns an interval that includes that returned by Marzullo's algorithm but may be larger since it will include the center points. This larger interval allows using additional statistical data to select a point within the interval, reducing the [[jitter]] in repeated execution.

==Method==