Intersection algorithm

The intersection algorithm is an agreement algorithm used to select sources for estimating accurate time from a number of noisy time sources. It forms part of the modern Network Time Protocol and is a modified form of Marzullo's algorithm. Marzullo's algorithm returns the smallest interval consistent with the largest number of sources, but that interval does not necessarily include the center point, the calculated offset, of all the sources in the intersection. The intersection algorithm returns an interval that includes the one returned by Marzullo's algorithm but may be larger, since it also includes those center points. The larger interval allows additional statistical data to be used to select a point within it, reducing the jitter in repeated execution.