The Complexity Of Traffic Grooming In Optical Path Networks With Egress Traffic
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The Complexity of Traffic Grooming in Optical Path Networks with Egress Traffic
Keywords: lightpaths, virtual topology, NP-Completeness.
The Complexity of Traffic Grooming in Optical Path Networks with Egress Traffic
We consider the problem of minimizing network costs when grooming traffic in optical networks that support Wavelength Division Multiplexing (WDM). While the general problem has been shown to be NP-Hard for a number of cost measures, there still exist restricted problems for which no complexity bound is known. In this research, we restrict our attention to traffic grooming for path networks with egress (all-to-one) traffic. This restricted model has practical significance for high speed (optical) access networks and can also lead to better bounds and approximations on more general network topologies (such as ring and star networks) that can be decomposed into path networks. Three important cost measures for this restricted model are studied. The first cost measure is the total number of ADMs used by the solution. Minimizing this cost was known to be NP-Complete even for egress traffic without using cross connects. We show that allowing an unbounded number of wavelengths obviates the need for digital cross connects at the nodes and hence the problem remains NP-Complete even when cross connects are allowed. The second cost measure is the number of transceivers used by the solution. We show that the problem of minimizing the number of transceivers is NP-Complete, even when restricted to egress traffic. We then develop a simple approximation scheme where the transceiver cost exceeds the minimum by at most the number of required wavelengths. Finally, we show that under certain conditions, there exist solutions that simultaneously minimize both ADM and transceiver costs. The third cost model aims to minimize the total electronic switching in the network. For this cost measure, we develop a polynomial time algorithm to determine the cost and structure of an optimum solution when the wavelength capacity constraint is relaxed. A closed form expression to determine the minimum cost is presented for problem instances with uniform traffic. We observe that these costs provide a l.
Traffic Grooming for Optical Networks
Author: Rudra Dutta
language: en
Publisher: Springer Science & Business Media
Release Date: 2008-08-06
The objective of this book is to provide timely and comprehensive coverage of the principles, technology, practice, and future of tra?c grooming in op- cal networks. Tra?c grooming considerations are already shaping new switch designs and standards, including next generation Synchronous Optical N- work/Synchronous Digital Hierarchy (SONET/SDH) and Generic Framing Procedure (GFP), are a?ecting future optical network technologies, and are creating new business opportunities. Yet information on the topic is sc- tered and there is a shortage of technical sources where relevant material can be accessed in a single location. The motivation for this book was to bridge this gap by providing a single authoritative point of reference to the tra?c grooming state of the art. Tra?c grooming is a complex subject, involving a number of interrelated concepts, standards, and technologies. It is also a rapidly growing ?eld of study,makingitdi?cultforasinglebooktocoverallaspectsindetail.Tocope with this scope and complexity, this book provides appropriate background information, followed by an in-depth study of a few key issues and challenges. It has been our intention to bring together a broad range of perspectives from preeminent researchers in both academia and industry. We believe that these multiple, diverse points of view add considerable value and make the contents more interesting to the reader.