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2014 | Buch

Introduction to Optical Networks Kapitel lesen Erstes Kapitel lesen

Optical Network Design and Planning

verfasst von: Jane M. Simmons

Verlag: Springer International Publishing

Buchreihe : Optical Networks

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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Über dieses Buch

This book takes a pragmatic approach to deploying state-of-the-art optical networking equipment in metro-core and backbone networks. The book is oriented towards practical implementation of optical network design. Algorithms and methodologies related to routing, regeneration, wavelength assignment, sub rate-traffic grooming and protection are presented, with an emphasis on optical-bypass-enabled (or all-optical) networks. The author has emphasized the economics of optical networking, with a full chapter of economic studies that offer guidelines as to when and how optical-bypass technology should be deployed. This new edition contains: new chapter on dynamic optical networking and a new chapter on flexible/elastic optical networks. Expanded coverage of new physical-layer technology (e.g., coherent detection) and its impact on network design and enhanced coverage of ROADM architectures and properties, including colorless, directionless, contentionless and gridless. Covers ‘hot’ topics, such as Software Defined Networking and energy efficiency, algorithmic advancements and techniques, especially in the area of impairment-aware routing and wavelength assignment. Provides more illustrative examples of concepts are provided, using three reference networks (the topology files for the networks are provided on a web site, for further studies by the reader). Also exercises have been added at the end of the chapters to enhance the book’s utility as a course textbook.

Inhaltsverzeichnis

Frontmatter
1. Introduction to Optical Networks
Abstract
An optical network is composed of the fiber-optic cables that carry channels of light, combined with the equipment deployed along the fiber to process the light. There has been a gradual migration from an architecture where the optical network served simply as a collection of static pipes to one where it is viewed as another networking layer. In the optical networking paradigm, functions such as routing and protection are supported at the granularity of a wavelength, which can be operationally very advantageous. One of the most transformative innovations has been the advent of optical bypass technology, which allows a signal to remain in the optical domain for all, or much, of its path from source to destination. Maintaining signals in the optical domain allows a significant amount of equipment to be removed from the network and provides a scalable trajectory for network growth. This chapter presents a brief history of optical networking and an overview of its current state. Additionally, it discusses relevant research trends, to provide insight into future optical networking advancements.
Jane M. Simmons
2. Optical Network Elements
Abstract
The dramatic shift in optical-network architecture that began in the 2000 time frame is chiefly due to the development of advanced optical network elements. These elements are based on the premise that the majority of the traffic that enters a network site is being routed through the site en-route to its final destination as opposed to being destined for the site. The deployment of optical bypass technology, which allows transiting traffic to remain in the optical domain, greatly reduces the amount of required network equipment. The optical-bypass-enabling network element known as the reconfigurable optical add/drop multiplexer (ROADM) is the focus of this chapter. Various ROADM architectures and their trade-offs are presented, along with numerous designs that illustrate operational alternatives. The chief attributes that affect the flexibility, cost, and efficiency of ROADMs are covered, including the colorless, directionless, contentionless, and gridless properties. Integration of elements within the nodal equipment is a more recent development, motivated by the desire to eliminate individual components, reduce cost, and improve reliability. The range of possible integration levels is illustrated by the discussions regarding integrated transceivers, integrated packet-optical platforms, and photonic integrated circuits.
Jane M. Simmons
3. Routing Algorithms
Abstract
Routing is the process of selecting a path through the network for a traffic demand, where it is important to consider factors such as cost, distance, and number of nodes traversed. Several routing strategies are discussed, with a focus on methodologies that have proved to be effective in practical optical networks. Routing for both long-term and real-time network planning is covered. The former emphasizes finding optimal solutions, whereas the latter requires more detailed network modeling to ensure the result is compatible with the equipment that is already deployed in the network. Strategies for protected routing are also presented, where two or more diverse paths are established to enable recovery from a failure. Multicast routing, from one source to multiple destinations, is discussed in detail. This encompasses “manycast” routing, where one source communicates with a subset of possible destination nodes; this is relevant for applications such as cloud computing. Finally, multipath routing is covered, where a demand is split into multiple lower-rate streams and routed over more than one path. The challenge is finding a path set where the difference in delay among the paths is below an acceptable threshold.
Jane M. Simmons
4. Regeneration
Abstract
In optical-bypass-enabled networks, an important aspect of the planning process is selecting the regeneration sites for a connection, if any. Regeneration “cleans up” the optical signal, typically by reamplifying, reshaping, and retiming it. Paths are usually selected to minimize the amount of required regeneration, as regeneration adds to the network cost and reduces the reliability of a path. The first portion of this chapter discusses various optical impairments and system properties that have an impact on when a signal must be regenerated, and addresses how these factors can be efficiently incorporated in network planning algorithms. The discussion then moves from the physical-layer aspects of regeneration to the architectural facets. Several regeneration architectures are presented, where the trade-off is between operational simplicity and cost. Finally, different options for actually implementing regeneration at a network site are presented. Again, there is a trade-off of operational flexibility versus cost.
Jane M. Simmons
5. Wavelength Assignment
Abstract
Wavelength assignment is an integral part of the network planning process in optical-bypass-enabled networks. Its need arises from the wavelength continuity property of optical bypass technology, where a connection that traverses a node all-optically must enter and exit the node on the same optical frequency. Thus, the wavelengths that are in use on one link may have ramifications for the wavelengths that can be assigned on other links. Effective wavelength assignment strategies, as covered in this chapter, must be utilized to ensure that wavelength contention is minimized. Wavelength assignment can be performed in concert with the routing process or it can be handled as a separate step; both approaches are discussed. Furthermore, as the underlying network technology grows more complex, more physical-layer impairments may need to be considered in the wavelength assignment process. Topics such as mixed line-rate networks, alien wavelengths, and maximizing the optical reach across the wavelength spectrum are addressed.
Jane M. Simmons
6. Grooming
Abstract
As networking technology and services have evolved, one characteristic that has persisted is that much of the traffic requires a service rate that is less than that of a full wavelength. This necessitates traffic grooming, where multiple client signals are carried on a wavelength in order to efficiently utilize the network capacity. For cost and architectural reasons, grooming switches may be deployed in only a subset of the network nodes. Methodologies for selecting the grooming nodes, and strategies for delivering traffic to these sites from the non-grooming nodes, are discussed. Scalability of grooming switches has become a challenge, especially for Internet Protocol (IP) routers, with the largest impediment being power consumption. Both near-term and long-term architectural approaches to deal with these scalability issues are enumerated. An algorithm that produces efficient grooming designs and that incorporates several cost versus capacity trade-offs is presented.
Jane M. Simmons
7. Optical Protection
Abstract
Protection against failures, by providing alternative paths or backup equipment, is a necessary component of network design. This chapter covers some of the major classes of protection and their inherent trade-offs, including dedicated versus shared protection, client-side versus network-side protection, ring versus mesh protection, and failure-dependent versus failure-independent protection. In addition to describing the properties of these protection classes, the discussion addresses how the presence of optical bypass affects the efficacy of the various schemes. Recovery from multiple concurrent failures, including an analysis of catastrophic failures, is covered as well. Schemes that are especially well suited for optical-bypass-enabled networks, and schemes that challenge the conventional wisdom that protection must trade off capacity for speed (e.g., network coding) are presented. The final section addresses fault localization, where again the focus is on optical-bypass-enabled networks.
Jane M. Simmons
8. Dynamic Optical Networking
Abstract
Transport optical networks today are typically quasi-static, with connections often remaining established for months or years. As an initial transition from this relatively fixed environment, transport optical networks are becoming configurable. The next step in this evolution is dynamic networking, where connections can be rapidly established and torn down without the involvement of operations personnel. After examining the motivation for dynamic optical networking, the remainder of the chapter presents implementation details. This includes an in-depth look at centralized versus distributed control-plane architectures. The challenges of dynamic networking in the presence of optical bypass or in a multi-domain environment are covered as well. In order for networks to be reconfigured remotely through software, the required equipment must already be deployed in the network. Techniques for estimating the amount of equipment to deploy at a node are presented. As a glimpse into possible future directions of optical networking, the implications of Software-Defined Networking relative to a dynamic optical layer are discussed.
Jane M. Simmons
9. Flexible Optical Networks
Abstract
Historically, network technology has largely been “one size fits all”; for example, a transmitter card generates a single data rate with a specified optical reach. The flexible approaches discussed in this chapter allow telecommunications carriers to tune the technology to better match the characteristics of the current network traffic. As with most shifts in networking paradigms, one of the major drivers behind the trend towards greater flexibility is ultimately cost. However, the more imminent impetus is the desire to use fiber capacity more efficiently. After discussing fiber capacity limits and their implications, the remainder of the chapter examines mining greater utilization from current systems by using bandwidth more efficiently. One major line of attack is allowing more flexible usage of the fiber spectrum, including both flexible-grid and gridless architectures. The anticipated benefits of these architectures are probed, along with their technological and operational challenges. Programmable technology, e.g., transponders that trade off optical reach and data rate, is another avenue that is being pursued.
Jane M. Simmons
10. Economic Studies
Abstract
Several network studies are presented that investigate various properties of optical networks, especially with regard to the economics of optical bypass. The studies are intended to provide guidance on how best to evolve a network as traffic levels continue to grow, and also to shed light on some of the desirable properties for a system vendor's portfolio. It includes investigations into speculative technology, where the studies identify trends and uncover the strengths and weaknesses of the various schemes in order to provide guidance with respect to future development efforts.
Jane M. Simmons
11. C-Code for Routing Routines
Abstract
The C-code for several useful routing functions is provided. The first set of routines uses the Breadth-First Search method to find a shortest path between a source and a destination. If there are multiple paths tied for the shortest, it finds the shortest path with the fewest number of hops in the path, which can be beneficial in network design. The second set of routines finds the K-shortest paths between a source and a destination. The third set of routines finds N mutually disjoint paths between a source and a destination. It can enforce link disjointness or both link-and-node disjointness. In scenarios where N totally disjoint paths do not exist, the function can be used to find the N maximally disjoint paths. The last two sets of routines find a multicast tree among a set of nodes. The code for all of the routines should be portable to any standard C compiler.
Jane M. Simmons
Backmatter
Metadaten
Titel
Optical Network Design and Planning
verfasst von
Jane M. Simmons
Copyright-Jahr
2014
Electronic ISBN
978-3-319-05227-4
Print ISBN
978-3-319-05226-7
DOI
https://doi.org/10.1007/978-3-319-05227-4

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