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In Optical Networks: Third Generation Transport Systems, leading telecom consultant Uyless Black presents an authoritative introduction to the emerging technologies that will drive the next communications revolution. From MPLS to Optical-over-IP to the new Optical Link Management Protocol (OLMP), Black's expert explanations and practical insight will be invaluable to every professional building, deploying, or managing optical networks. Engineers new to the field will especially appreciate his review of current fiber systems, signaling, SONET/SDH standards, and how these technologies lay the foundation for tomorrow's 3G advances.
Optical Networks: Third Generation Transport Systems is the first book to cover every key optical technology for building networks of unprecedented power, flexibility, and manageability.
The first column in the table is the name (or names) usually associated with the technology. The first generation systems are known as T1 or E1. The second generation systems are called SONET (for the Synchronous Optical Network) or SDH (for the Synchronous Digital Hierarchy). These terms are explained in more detail in later parts of this book. However, the industry has not yet settled on a handle for the third generation digital carrier network, but the term Optical Transport Network (OTN) is widely used. The second column identifies the generation family.
The third column shows what kinds of user payloads the networks are designed to support. Although the first and second generation networks are designed to support voice traffic, they can and do transport data and video images. But they are not "optimized" for data and video traffic. In contrast, the 3G transport network is designed to support voice, video, or data payloads. When used with multiprotocol label switching (MPLS), resource reservation protocol (RSVP), and DiffServ, as well as some of the new specifications dealing with optical bandwidth on demand, they are also designed to provide tailored quality-of-service (QOS) features for individual customers. The point will be made repeatedly in this book that the 3G transport network no longer consists of fixed, static "pipes" of capacity; it can dynamically change to meet the changing requirements of its users.
The third column also contains the notations of Non-BOD or BOD. The first and second generation systems are not designed to provide bandwidth of demand (BOD). The bandwidth is configured with crafting operations at each node. 3G systems are more dynamic and allow bandwidth to be requested on demand.
The fourth column lists the predominant multiplexing schemes, TDM or WDM. The fourth column also lists the manner in which the networks switch traffic when they were first deployed (at their inception). First generation systems were solely E/E/E operations: (a) they accepted electrical signals (the first E), (b) processed them (the second E), and (c) sent them to another node (the third E). Second generation systems are O/E/O operations: (a) they accept optical signals (the first O), (b) convert them to electrical signals for processing (the E), and (c) convert the electrical signals back to optical signals for transmission (the second O). Third generation systems are intended to be all optical (O/O/O), in that they process optical payloads, and do not need to convert the bits to electrical images for processing. Today, all three generations are mainly O/E/O oriented.
The fifth column lists the principal media used by the technologies at their inception, as well as the time that these networks were first introduced into the industry. All three generations now use a combination of copper, fiber, and wireless media.
The sixth column lists the typical capacity of the generation. It is evident that each succeeding family has increased its transport capacity by orders of magnitude.
The seventh column goes hand-in-hand with the third column ("Designed For"). The first and second generation networks were designed for fixed-length voice traffic, based on the 64 kbit/s payload, with a 125-µsec clocking increment. The third generation network supports this signal, but also supports variable-length payloads, an important capability for carrying data traffic. As well, the first and second generation networks can carry variable-length traffic, but they are not very efficient in how they go about transporting variable-length data traffic.
The eighth column explains whether any of the generations were designed to interwork with and directly support other protocols. T1/E1 was not so designed; again, 1st generation transport systems were set up to support voice traffic. Any efforts to devise methods of carrying other payloads were an afterthought and in vendor-specific procedures. With the advent of 2nd generation systems with SONET/SDH, efforts were made by the standards groups to define procedures for carrying certain kinds of data traffic, and many manufacturers adapted these standards into their products.
3rd generation transport networks are geared toward supporting many kinds of payloads, and specifically the Internet, ATM, and MPLS protocol suites. As we shall see as we proceed though this book, extensive research has resulted in many specifications defining how MPLS contributes to the operations of the third generation digital (optical) transport network.
As depicted in Figure 1–1, a terabit fiber carries 1012 bits per second. At this rate, the fiber can transport just over 35 million data connections at 28.8 kbit/s, or about 17 million digital voice channels, or just under 500,000 compressed TV channels (or combinations of these channels).
Even the seasoned telecommunications professional pauses when thinking about the extraordinary capacity of optical fiber.
A logical question for a newcomer to optical networks is, why are they of much greater capacity than, say, a network built on copper wire, or coaxial cable? The answer is that optical signals used in optical networks operate in a very high position and range of the frequency spectrum, many orders of magnitude higher than electromagnetic signals.
Thus, the use of the higher frequencies permits the sending of many more user payloads (voice, video, and data) onto the fiber medium.
Figure 1–2 shows the progress made in the transmission capacity of optical fiber technology since 1980 [CHRA99]. The top line represents experimental systems, and the bottom line represents commercial systems. The commercial results have lagged behind the experimental results by about six years. The dramatic growth in the experimental capacity was due to improved laboratory techniques and the progress made in dispersion management, a subject discussed later in this book. As the figure shows, the transmission capacity of optical fiber has been growing at an extraordinary rate since the inception of the technology....
|Ch. 2||The Telecommunications Infrastructure||23|
|Ch. 3||Characteristics of Optical Fiber||34|
|Ch. 4||Timing and Synchronization||50|
|Ch. 5||SONET and SDH||71|
|Ch. 6||Architecture of Optical Transport Networks (OTNs)||89|
|Ch. 7||Wavelength Division Multiplexing (WDM)||112|
|Ch. 8||Network Topologies and Protection Schemes||127|
|Ch. 9||MPLS and Optical Networks||149|
|Ch. 10||Architecture of IP and MPLS-based Optical Transport Networks||166|
|Ch. 11||The Link Management Protocol (LMP)||193|
|Ch. 12||Optical Routers: Switching in Optical Internets||212|
|Ch. 13||ASON Operations at the User Network Interface (UNI) and the Network-to-Network Interface (NNI)||243|
|Ch. 14||ATM vs. IP in Optical Internets||259|
|Ch. 15||Optical Internets: Evolving to a 3G Architecture||281|
|App. A||The T1 Family||309|
This book describes third generation digital carrier transport networks. The primary focus of the book is on the role of optical fiber and optical routers in these networks, with the emphasis on wave division multiplexing (WDM). Third generation transport networks also entail considerable interworking with Multiprotocol Label Switching (MPLS), and this topic is covered in several chapters. As well, the ITU and the IETF are defining new multiplexing hierarchies for the third generation transport network, and these efforts are described in this book.
You might be wondering what are first and second generation transport networks? I classify first generation systems, introduced in the 1960s, as those that were/are built with predominately T1 and E1 architectures. I classify second generation systems, introduced in the 1980s, as those that were/are built with SONET and SDH architectures. Although these topics are covered in this book, the emphasis is on networks that go beyond these older technologies.
The emphasis of this book is on newer technologies, being introduced as you read this preface, with the focus on optical internets: those dealing with IP over optical; label switching with WDM; optical cross-connects; optical routers; optical bandwidth on demand; and the emerging Optical Transport Network (OTN), published by ITU-T and amplified by the IETF. For the newcomer, Chapter 3 provides tutorials on the basics of optical technology, including the operations of optical fiber and lasers.
I want to emphasize that this book has only one chapter on the technology of optical fiber itself. Scores of books are available on this subject, and myintent is to move beyond the descriptions of a light signal on a fiber. I think Chapter 3 will be sufficient for the newcomer on the subject of optical fiber, and I provide you with some excellent references if you wish to delve into more details about the subject.
A considerable portion of this book is devoted to explaining many Internet-based specifications pertaining to IP-based optical networks.
Keep in mind that the Internet drafts are works in progress, and should be viewed as such. You should not use the drafts with the expectation that they will not change. Notwithstanding, if used as general tutorials, the drafts discussed in this book are "final enough" to warrant their explanations. Indeed, many of my clients use these drafts in their product planning and design.
For all the Internet standards and drafts the following applies:
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