Ping-pong scheme

A ping-pong scheme is a pattern used across different areas of software engineering in which an algorithm's behavior alternates back and forth between two entities rather than proceeding through a single continuous sequence. What plays the role of the two alternating entities changes with the setting: it might be two communication partners exchanging turns in a protocol, two network paths a system switches between, or two sets of file blocks processed in turn. The unifying feature across these otherwise different applications is the back and forth alternation itself, which gives the pattern its name from the back and forth motion of the ball in the game of table tennis. Because the same alternating shape recurs in unrelated fields, the term is applied descriptively rather than naming one single formal algorithm.