Wavelength-division multiplexing (WDM) technology is emerging as the transmission and switching mechanism for future optical mesh networks. In these networks it is desired that a wavelength can be routed without electrical conversions. Two technologies are possible for this purpose: wavelength selective cross-connects (WSXC) and wavelength interchanging cross-connects (WIXC), which involve wavelength conversion. It is believed that wavelength converters may improve the blocking performance, but there is a mix of results in the literature on the amount of this performance enhancement. We use two metrics to quantify the wavelength conversion gain: the reduction in blocking probability and the increase in maximum utilization, compared to a network without converters. We study the effects of wavelength routing and selection algorithms on these measures for mesh networks. We use the overflow model to analyze the blocking probability for wavelength-selective (WS) mesh networks using the first-fit wavelength assignment algorithm. We propose a dynamic routing and wavelength selection algorithm, the least-loaded routing (LLR) algorithm, which jointly selects the least-loaded route-wavelength pair. In networks both with and without wavelength converters the LLR algorithm achieves much better blocking performance compared to the fixed shortest path routing algorithm. The LLR produces larger wavelength conversion gains; however, these large gains are not realized in sufficiently wide utilization regions and are diminished with the increased number of fibers.

Effects of wavelength routing and selection algorithms on wavelength conversion gain in WDM optical networks

Unlike traditional routing schemes that route all traffic along a single path, multipath routing strategies split the traffic among several paths in order to ease congestion. It has been widely recognized that multipath routing can be fundamentally more efficient than the traditional approach of routing along single paths. Yet, in contrast to the single-path routing approach, most studies in the context of multipath routing focused on heuristic methods. We demonstrate the significant advantage of optimal (or near optimal) solutions. Hence, we investigate multipath routing adopting a rigorous (theoretical) approach. We formalize problems that incorporate two major requirements of multipath routing. Then, we establish the intractability of these problems in terms of computational complexity. Finally, we establish efficient solutions with proven performance guarantees.

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Multipath routing algorithms for congestion minimization

Wavelength division multiplexed point-to-point transport is becoming commonplace in wide area networks. With the expectation that the next step is end-to-end networking of wavelengths (in the optical domain without conversion to electronics), there is a need for new design techniques, a new understanding of the performance issues, and a new performance evaluation methodology in such networks. This paper describes approaches to that end, summarizes research results, and points to open problems.

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Performance of WDM transport networks

A fallback strategy for a system (700) and method (200) is provided for rerouting a call that fails to be established utilizing a first set of constraints in a communication network system. This strategy enables the communication network system to utilize a look-around-first type of preemption that avoids unnecessary preemption and provides alternate routing for a call according to predetermined constraints selected by a user.

System and method for call-by-call source routing with rule-based fallbacks

Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). We study the problems of routing and wavelength converter placement in optical networks with sparse wavelength conversion. We propose a new dynamic routing algorithm with two new path cost functions based on the concept of least-load routing (LLR) with sparse converter placement, and we discuss the application of genetic algorithms (GAs) to determine the optimal location of wavelength converters so that the call-blocking probability is minimized. Simulation results show that the proposed dynamic routing algorithms perform significantly better than shortest-path (SP) routing and fixed-alternative routing (FAR) in terms of the call-blocking probability. The GA model is able to obtain a nearly optimal solution of the wavelength converter placement problem within a reasonable time, and its performance is better than that of two other popular heuristic placement algorithms.

/pdf/wavelength-converter-placement-in-least-load-routing-based-3u6xz2lig8.pdf

Wavelength converter placement in least-load-routing-based optical networks using genetic algorithms

Dynamic network evolution achieves network performance improvement and cost reduction by taking advantage of new advanced technologies being introduced into the network to achieve greater network flexibility and efficiency. The author describes the evolution of dynamic networks, with examples drawn from the AT&T DNHR network deployed in the '80s and RTNR network deployed in the '90s. Dynamic traffic routing implements an integrated class-of-service routing feature for extending dynamic routing to emerging services, and provides a self-healing network capability to ensure a network-wide path selection and immediate adaptation to failure. Dynamic traffic routing brings benefits to customers in terms of new service flexibility and improved service quality and reliability, at reduced cost. >

Dynamic network evolution, with examples from AT&T's evolving dynamic network

Dynamic routing concepts are described, and the design and control of dynamic routing networks is discussed. The vastly improved performance of the networks is illustrated with examples from operational experience. The evolution of dynamic routing with respect to several future directions is highlighted. These directions are extension to new networks and services, robust design and real-time adaptivity, and extension to interconnecting networks, including the Worldwide Intelligent Network. >

http://ieeexplore.ieee.org/iel1/35/2196/00060365.pdf

G.R. Ash

Papers

Dynamic network evolution, with examples from AT&T's evolving dynamic network

Design and control of networks with dynamic nonhierarchical routing