Some constraints and tradeoffs in the design of network communications

A number of properties and features of interprocess communication systems are presented, with emphasis on those necessary or desirable in a network environment. The interactions between these features are examined, and the consequences of their inclusion in a system are explored. Of special interest are the time-out feature which forces all system table entries to “die of old age” after they have remained unused for some period of time, and the insertion property which states that it is always possible to design a process which may be invisibly inserted into the communication path between any two processes. Though not tied to any particular system, the discussion concentrates on distributed systems of sequential processes (no interrupts) with no system buffering.