NETWORKED SYSTEMS RELIABILITY Many physical problems (e.g., computer networks, piping systems, and power grids) can be modeled by a network. In the context of this chapter, the word network means a physical problem that can be modeled as a mathematical graph composed of nodes and links (directed or undirected) where the branches have associated physical parameters such as flow per minute, bandwidth, or megawatts. In many such systems, the physical problem has sources and sinks or inputs and outpu