and impairments that prevent the extension of transparency beyond a certain point. Routing in optical mesh networks Routing is a key control and operational aspect of optical mesh networks. In transparent or all-optical networks, routing of connections is tightly linked to the wavelength selection and assignment process (so-called Routing and Wavelength Assignment, or "RWA"). This is due to the fact that the connection remains on the same wavelength from end-to-end throughout the network (sometimes referred to as wavelength continuity constraint, in the absence of devices that can translate between wavelengths in the optical domain). In an opaque network, the routing problem is one of finding a primary path for a connection and if protection is needed, a backup path diverse from the primary path. Wavelengths are used on each link independently of each other's. Several algorithms can be used and combined to determine a primary path and a diverse backup path (with or without sharing of resource along the backup path) for a connection or service, such as: shortest path, including Dijkstra's algorithm; k-shortest path, such as Yen's algorithm; edge and node-diverse or disjoint routing, including Suurballe's algorithm; and numerous heuristics. In general, however, the problems of optimal routing for Dedicated Backup Path Protection with arbitrary Shared Risk Link Groups (SRLGs), and for Shared Backup Path Protection are NP-complete. Applications The deployment of optical mesh networks is enabling new services and applications for service providers to offer their customers, such as Quality of Service (QoS) protection, allowing services with different levels of protection: pre-emptable, unprotected, protected with guaranteed recovery against single link or single node failure, protected against multiple failures (through a combination of protection and restoration) Dynamic services such as Bandwidth-on-Demand (BoD), Just-In-Time (JIT) bandwidth, bandwidth scheduling, and bandwidth brokering Optical virtual private networks Multicast lightpaths It also supports new network paradigms such as IP-over-optical network architectures Related network architectures Mesh networking in general and wireless mesh networking in particular. See also Telecommunications and networking Computer network Multiwavelength optical networking Optical Transport Network Wavelength switched optical network Telecommunications Wireless mesh networks Telecommunications equipment Cross-connect Wavelength division multiplexing Packet networking Internet protocol Multiprotocol Label Switching Optical burst switching Router Connection-oriented networking Circuit switching Connection oriented Availability Availability References Further reading "Site on Network Protection - network protection techniques, network failure recovery, network failure events" "Mesh-based Survivable Transport Networks: Options and Strategies for Optical, MPLS, SONET and ATM Networking", by Wayne