Absttact-Failure resilience is one the desired features of the Internet. Multiple link failure models, in the form of Shared-Risk Link Group (SRLG) failures, are becoming critical in survivable optical network design. Most of the traditional restoration schemes are based on the single-failure assumption which is unrealistic. In our research, we propose a novel survivability approach that can tolerate multiple failures arising out of SRLG situations. Each network has a set of sub-graphs that can be created by removing each of the links in the network and, in addition, removing all of the links of a SRLG. Connections in the newly proposed strategy are accepted if they can be routed in all the sub-graphs, and are protected against all single link and SRLG failures.We also study how restorability can be achieved for node failures and analyze the performance of our approaches for different network topologies. Our proposed restoration architecture requires the storage of network state information corresponding to each of the possible failure scenarios defined by the subin current WDM backbone networks.graphs. This restoration model is novel and can be implemented 0-7803-81 18-1/03/$17.00 0 2003 IEEE

All-optical networks are able to transport data from source to destination entirely in the optical domain. This is a departure from current optical networks that rely on optical-electrical-optical (OEO) conversion at each intermediate connection node to route data properly. The opacity inherent in traditional networks is costly in terms of limiting bandwidth and increasing switching complexity. MPLS, OBS and OPS have been proposed as solutions for realizing an all-optical network. MPLS and OBS have the advantages of creating all-optical connections between nodes, but do not allow intermediate nodes to use the wavelength as well. Additionally, optical switches are constantly being reconfigured to accommodate new connections. OPS can make switching decisions in the optical domain, but the technology is immature. Light trail technology tries to avoid the pitfalls of immature technology, the inability of intermediate nodes to use a connection wavelength, and the constant reconfiguration of switches. A light trail is a unidirectional optical bus between nodes that allows intermediate nodes to access the bus. The goal is to minimize the amount of active switching that needs to be done by allowing intermediate nodes to use a connection that has already been setup. Connections are not constantly being setup and torn down, but rather exist for as long as they are being used by any of the nodes along their light trail.

Double link failure models, in which any two links in the network fail in an arbitrary order, are becoming critical in survivable optical network design. A significant finding is that designs offering complete dual-failure restorahility require almost triple the amount of spare capacity.In this paper, networks are designed to achieve 100% restorability under single link failures, while maximizing coverage against any second link failure in the network. In the event of a single link failure, the restoration model attempts to dynamically find a second alternate link-disjoint end-to-end path to provide coverage against a sequential overlapping link failure. Sub-graph routing [l] is extended to provide dual-failure restorahility for a network provisioned to tolerate all single-link failures. This strategy is compared with shared-mesh protection.The results indicate that subgraph routing can achieve overlapping second link failure restorability for 9599% of connections. It is also observed that subgraph routing can inherently provide complete dual-failure coverage for -7241% of the connections.

Ripple-carry architectures are the norm in today's reconfigurable fabrics. They are simple, require minimal routing, and are easily formed across arbitrary cells in a fabric. However, their computation delay grows linearly with operand width. Many different fabric carry-chains have been presented in literature offering non-linear delays, but generally require a significant investment in routing and processing area. Carry-skip chains are well-known in arithmetic logic design, and although they too possess a linear delay, their performance is 2x or more faster than simple ripple-carry schemes. They require an expanded carry chain and minimal extra logic, but offer impressive speed-ups for arithmetic. This paper presents a reconfigurable cell that supports carry-skip arithmetic using a multi-bit carry chain achieving 2·k ·b+ n b performance, where b is the block size and k is an architecture constant. The cell is specialized for arithmetic and Boolean operations with reduced configuration memory. Additional resources are provided to reuse the multi-bit carry chain for 3-source operand arithmetic to explore how multi-bit chains can be reused.