Design of Survivable Networks Based on p-Cycles

p-Cycles are a recently discovered and promising new paradigm for surviv-able networking. p-Cycles simultaneously provide the switching speed and simplicity of rings with the much greater capacity-efficiency and flexibility for reconfiguration of a mesh network. p-Cycles also permit shortest-path routing of working paths (as opposed to ring-constrained working path routing), which adds further to network capacity efficiency. Operationally p-cycles are similar to BLSRs in that, upon failure, switching actions are required at only two nodes and both those nodes are fully pre-planned as to the actions that are required for any failure detected at their sites. With the optimization models in this chapter, entire survivable transport networks can be easily designed with essentially the same spare to working capacity (redundancy) ratios as optimized span-restorable mesh networks. p-Cycles thus bridge the ring versus mesh debate that dominated work in survivable networks through the 1990s and provide the best of both worlds: the efficiency of mesh with the speed of rings.