A fault recovery system that is fast and reliable is essential to today's networks, as it can be used to minimize the impact of the fault on the operation of the network and the services it provides. This paper proposes a methodology for performing automatic protection switching (APS) in optical networks with arbitrary mesh topologies in order to protect the network from fiber link failures. All fiber links interconnecting the optical switches are assumed to be bidirectional. In the scenario considered, the layout of the protection fibers and the setup of the protection switches is implemented in nonreal time, during the setup of the network. When a fiber link fails, the connections that use that link are automatically restored and their signals are routed to their original destination using the protection fibers and protection switches. The protection process proposed is fast, distributed, and autonomous. It restores the network in real time, without relying on a central manager or a centralized database. It is also independent of the topology and the connection state of the network at the time of the failure.

This paper investigates survivable lightpath provisioning and fast protection switching for generic mesh-based optical networks employing wavelength-division multiplexing (WDM). We propose subpath protection, which is a generalization of shared-path protection. The main ideas of subpath protection are: 1) to partition a large optical network into smaller domains and 2) to apply shared-path protection to the optical network such that an intradomain lightpath does not use resources of other domains and the primary/backup paths of an interdomain lightpath exit a domain (and enter another domain) through a common domain-border node. We mathematically formulate the routing and wavelength-assignment (RWA) problem under subpath protection for a given set of lightpath requests, prove that the problem is NP-complete, and develop a heuristic to find efficient solutions. Comparisons between subpath protection and shared-path protection on a nationwide network with dozens of wavelengths per fiber show that, for a modest sacrifice in resource utilization, subpath protection achieves improved survivability, much higher scalability, and significantly reduced fault-recovery time.

An aspect that is common to much of the work on optimized design of multiple-ring SONET (or WDM) networks is that they treat the design as a form of graph-covering problem. This produces fully restorable designs but there may be unnecessary lower bounds on network cost when the ring set has strictly to protect every span in the fiber graph. "Span elimination" is the problem of finding those key spans of an existing fiber graph on which it is more effective not to route any demands, thereby avoiding the requirement for ring coverage on the span. Preliminary results, with two algorithms, show significant cost reductions in the designs that emerge from a coverage-based solver arising from judicious span elimination prior to the graphcovering process. I. INTRODUCTION Bi-directional line-switched rings (BLSR) and unidirectional path-switched rings (UPSR) are now in common use for survivable transport networking [1]. These protection structures offer fast restoration speeds (typically unde...

Visualizing survivable telecommunication networks on the screen has proven to be useful and helpful for the network designers. In fact, they can easily identify rings, perceive the interaction between rings, and then rapidly spot possible problems. Given a ring cover of survivable telecommunication networks, we provide three techniques for drawing a ring cover. Our proposed algorithms produce drawings that require O(n 2 ) area, where n is the number of nodes in the ring cover. 1. Introduction The problem of drawing a graph in the plane has received increasing attention recently due to the large number of applications stated in [1]. The design and analysis of telecommunication network is a very important area (for more details see [2] and [3]). In this paper, we study techniques for visualizing telecommunication networks. We are motivated to design a network which (1) satisfies the traffic requirements, (2) can survives failures, and (c) the cost of the network is minimum. A network...