Janos is an operating system for active network nodeswhose primary focus is strong resource management andcontrol of untrusted active applications written in Java.Janos includes the three major components of a Java-basedactive network operating system: the low-level NodeOS, aresource-aware Java Virtual Machine, and an active networkprotocol execution environment.Each of these componentsis separately usable.This article lays out the Janosdesign and its rationale.