A method and apparatus for generating first and second tree topologies for any source node in a network which can be represented as a node or an edge redundant graph, such that any node in the graph remains connected to the source node via at least one tree even after the failure of a node or an edge. This technique provides a recovery mechanism upon detection of a failure in a network.

Method and apparatus for automatic protection switching

A new architecture for implementing unidirectional and bidirectional self-healing interoffice ring networks using wavelength division multiplexing (WDM) technology for growth is proposed. The working ring uses all-optical drop-and-add multiplexers at each office and the protection path uses optical amplifiers and optical switches. The use of WDM technology, combined with all-optical drop-and-add multiplexers, accommodates growth to a network capacity of more than 1 Tb/s. >

http://ieeexplore.ieee.org/iel2/3171/8993/00397474.pdf

Multiwavelength survivable ring network architectures

The authors present a new approach for trunk network survivability. This modular approach is intended for a telephone trunk network consisting of high-bandwidth fiber-optic links connected through reconfigurable digital cross-connect nodes. It works for both node and link failures. This approach comprises a distributed protocol with two parts. First, the surviving digital cross-connect nodes are caused to converge to an agreement on the topology (i.e., what is up and what is down). Second, based on the agreed topology and on a precomputed plan for that topology, the digital cross-connect nodes are reconfigured to restore as much call-carrying capacity as possible. The modularity of this approach comes from separating the problem of devising a distributed fault-tolerant protocol to determine what the failure is from the problem of designing a network reconfiguration for that failure. >

Using distributed topology update and preplanned configurations to achieve trunk network survivability

We study the problem of designing a three level hub network where the top level consists of a complete network connecting the so-called central hubs and the second and third levels are unions of star networks connecting the remaining hubs to central hubs and the demand centers to hubs and central hubs, respectively. The problem is to decide on the locations of a predetermined number of hubs and central hubs and the connections in order to minimize the total routing cost in the resulting network. This problem includes the classical p-hub median problem as a special case. We also consider a version of this problem where service quality considerations are incorporated through delivery time restrictions. We propose mixed integer programming models for these two problems and report the outcomes of a computational study using the CAB data and the Turkey data.

/pdf/the-hierarchical-hub-median-problem-with-single-assignment-ljhu9xw00e.pdf

The hierarchical hub median problem with single assignment

Current means of providing loop-back recovery, which is widely used in SONET, rely on ring topologies, or on overlaying logical ring topologies upon physical meshes. Loop-back is desirable to provide rapid preplanned recovery of link or node failures in a bandwidth-efficient distributed manner. We introduce generalized loop-back, a novel scheme for performing loop-back in optical mesh networks. We present an algorithm to perform recovery for link failure and one to perform generalized loop-back recovery for node failure. We illustrate the operation of both algorithms, prove their validity, and present a network management protocol algorithm, which enables distributed operation for link or node failure. We present three different applications of generalized loop-back. First, we present heuristic algorithms for selecting recovery graphs, which maintain short maximum and average lengths of recovery paths. Second, we present WDM-based loop-back recovery for optical networks where wavelengths are used to back up other wavelengths. We compare, for WDM-based loop-back, the operation of generalized loop-back operation with known ring-based ways of providing loop-back recovery over mesh networks. Finally, we introduce the use of generalized loop-back to provide recovery in a way that allows dynamic choice of routes over preplanned directions.

/pdf/generalized-loop-back-recovery-in-optical-mesh-networks-pgsefhgkj3.pdf

Generalized loop-back recovery in optical mesh networks

A class of survivable network architectures and a fiber network design model to study quantitative tradeoffs between cost and survivability for each candidate network architecture are discussed. The network architectures studied fall into two categories: conventional architectures are those using present and future technologies, respectively. The model network used in this study is a metropolitan intralocal access transport area (LATA) network. For the near term, the study show that a 'single homing' architecture with 1:N diverse protection provides affordable survivability for fiber cable cuts. The percentage of model circuits protected from link failures is raised from 50%-72% for only 6.3% increase in cost. For future architectures, the self-healing rings could both improve survivability and reduce costs. >

T.-H. Wu

Papers

Survivable network architectures for broad-band fiber optic networks: model and performance comparison