Sonet and T1: Architectures for Digital Transport Networks / Edition 2 available in Hardcover
- Pub. Date:
- Pearson Education
- The definitive SONET guide, fully updated for the latest technologies and standards
- In-depth coverage of SONET operations, administration, and management
- New coverage: IP-over-SONET optical Internets, WDM integration, MPLS, and much more
- All new chapter on SDH and SONET/SDH interworking
The professional's guide to SONETcompletely updated for the latest innovations!
SONET is the transport technology at the heart of virtually every high-speed optical network. SONET and T1: Architecture for Digital Transport Networks, Second Edition gives communications engineers and other professionals an in-depth understanding of every facet of SONET technology-including breakthrough IP-over-SONET optical Internets, new techniques for integrating SONET with WDM fiber, and other key innovations.
The authors begin with an overview of SONET's goals and architecture, then present the most detailed coverage of SONET operations, administration, and management available in any book. SONET and T1: Architecture for Digital Transport Networks, Second Edition offers detailed information on the "hows" and "whys" of deploying and managing any SONET system, from architecture through maintenance, using real-life applications drawn from diverse carrier and business environments. This second edition's new coverage includes:
- New deployment examples for metropolitan and long-haul networks
- New passive optical applications
- New SONET network management solutions
- New coverage of SDH, the European SONET standard, and SONET/SDH interworking
- New techniques for expandincapacity with WDM
- IP-over-SONET: advantages, risks, and issues
- SONET and MPLS
From day-to-day administration to long-term planning, SONET and T1: Architecture for Digital Transport Networks, Second Edition is your richest, most up-to-date SONET resource.
|Series:||Prentice Hall Series in Advanced Communications Technologies|
|Product dimensions:||7.00(w) x 9.56(h) x 1.24(d)|
About the Author
Sharleen Waters has served for fifteen years as GTE Senior Technical Instructor in Broadband Technologies, training clients such as AT&T, Nortel, Siemens, Alcatel, NEC, and Fujitsu in installing, testing, and maintaining SONET equipment.
Read an Excerpt
1: IntroductionThis chapter introduces the Synchronous Optical Network (SONET) and T1 technology. A brief history of SONET is provided, as well as the reasons that SONET came into existence. We also provide a brief history of the T1 system and make a general comparison of T1 and SONET. As a prelude to later chapters, a general description is provided of the major features of SONET.
What Are SONET and T1?Digital carrier systems, such as the well-known T1 technology, have served the telecommunications industry well for over 40 years, and they shall continue to do so for quite some time. T1 was first installed in 1962 to provide a high-speed (1.544 Mbit/s) digital carrier system for voice traffic. It was modified later to support data and video applications. In terms of communications technology, 1962 is a very long time ago. Since this date, extraordinary progress has been made in the fields of computers and communications. Many of the technical underpinnings of SONET exploit this new technology.
We have cited T1 in a previous paragraph to help explain the nature of SONET. T1 and associated systems (such as T3 and similar technology in other parts of the world) are first-generation digital transport systems. SONET is a second-generation digital transport system. Like T1, its purpose is to transport, multiplex, and switch digital signals representing voice, video, and data traffic to and from users' applications. However, T1 and SONET differ significantly in how they accomplish these functions. Many facets of the T1 architecture are based on technology that is over four decades old. In contrast to T1, the SONET architecture is based on the technology of today. With this brief comparison in mind, let us take a look at how SONET came into existence and then examine some of the major features of SONET.
The Development of SONETSome people view SONET as a new technology, and it is only in the last decade that SONET has been deployed extensively. However, SONET did not just appear suddenly on the scene. Extensive research has been underway for well over a decade on many of the features that are found in SONET. One notable achievement began in 1984. It focused on the efforts of several standards groups and vendors to develop optical transmission standards for what is known as the mid-span meet (also known as transverse compatibility). The goal was to publish a specification that would allow different vendors' equipment to interoperate with each other at the fiber level.
In addition, due to the breakup of the Bell System in 1984, there were no standards developed beyond T3 technology. Prior to the divestiture, all equipment was built by AT&T's manufacturing arm, Western Electric (WECO), which ensured that there would be no compatibility problems in any network components.
After the breakup, there was little incentive for the other carriers (such as MCI and Sprint) to purchase AT&T-based equipment. Indeed, there was no incentive to purchase AT&T equipment, since AT&T, MCI, and Sprint had begun competing with each other for long distance services. This situation led to the rapid growth of alternate equipment vendors (such as Nortel Networks), who were developing advanced digital switching technologies.
The 1984 divestiture paved the way for alternate long distance carriers through the equal access ruling. The alternate carriers were given equal access to the local exchange carrier (LEC) infrastructure and connections to AT&T for end-to-end long distance service. The LEC could connect to MCI, Sprint, and others through their switching facilities at an interface in the LEC or long distance carrier offices called the point of presence (POP).
During this time, higher capacity schemes beyond T3 became proprietary, creating serious compatibility problems for network operators who purchased equipment from different manufacturers. In addition, the early 1980s witnessed the proliferation of incompatible and competing optical fiber specifications.
Precursors to SONETWe interrupt the discussion on divestiture to explain some of the technology that was being developed during the early 1980s. A landmark project that contributed to SONET was Metrobus, an optical communications system developed at AT&T's Bell Labs in the early 1980s. Its name was derived from its purpose: It was situated in a metropolitan area to serve as a high-speed optical transport network.
Metrobus demonstrated the feasibility of several new techniques that found their way into SONET. (They are explained in this chapter and subsequent chapters.) Among the more notable features were (a) single-step multiplexing, (b) synchronous timing, (c) extensive overhead for network management, (d) accessing low level signals directly, (e) point-to-multipoint multiplexing, and (f) the employment of multi-megabit media for achieving high bandwidth network transmission capacity (of approximately 150 Mbit/s).
This latter decision along with the ensuing research and testing was important, because a 150 Mbit/s signal rate can accommodate voice, video, and data signals, as well as compressed high definition television (HDTV). Moreover, these techniques permitted the use of relatively inexpensive graded-index multimode fibers instead of the more expensive single mode fibers, although single mode fiber is now the preferred media for SONET.
The various standards groups began the work on SONET after MCI send a request to them to establish standards for the mid-span meet. The SONET specifications were developed in the early 1980s, and Bellcore submitted its proposals to the American National Standards Institute (ANSI) T1X1 Committee in early 1985,1 based on a 50.688 Mbit/s transfer rate. The initial SONET work did not arouse much interest until the Metrobus activity became recognized.
Later, using the innovative features of Metrobus, the SONET designers made modifications to the original SONET proposal, principally in the size of the frame and the manner in which T1 signals were mapped into the SONET frame.
From 1984 to 1986, various alternatives were considered by the ANSI T1 Committee, who settled on what became known as the synchronous transport signal number one (STS-1) rate as a base standard. Finally, in 1987, the ANSI T1X1 committee published a draft document on SONET.
Participation by ITU-TDuring this time, the international standards body now known as the International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) had rejected the STS-1 rate as a base rate in favor of a base rate of 155.520 Mbit/s. For a while, it appeared that the North American and European approaches might not converge, but the SONET frame syntax and structure were altered one more time to a rate of 51.84 Mbit/s which permitted this rate to be multiplexed (concatenated) by an integer of three to the European preference of 155.52 Mbit/s. This work has resulted in almost complete compatibility between the North American and ITU-T approaches. The ITU-T Recommendations are now considered the "official" standards and are collectively called the Synchronous Digital Hierarchy (SDH).
Once the major aspects of the standards were in place, vendors and manufacturers began to develop SONET and SDH equipment and software. These efforts came to fruition in the early 1990s and, as of this writing, SONET and SDH have been deployed throughout the United States and other parts of the world.
Key ITU-T DocumentsListed below are some of the most commonly cited SDH standards available from the ITU-T.2
- ITU-T G.707: Network Node Interface for the Synchronous Digital Hierarchy (SDH)
- ITU-T G.781: Structure of Recommendations on Equipment for the Synchronous Digital Hierarchy (SDH)
- ITU-T G.782: Types and Characteristics of Synchronous Digital Hierarchy (SDH) Equipment
- ITU-T G.783: Characteristics of Synchronous Digital Hierarchy (SDH) Equipment Functional Blocks
- ITU-T G.803: Architecture of Transport Networks Based on the Synchronous Digital Hierarchy (SDH)
Role of ANSI and Key Standards DocumentsToday, ANSI coordinates and approves the SONET standards. The standards are developed by the T1 committee. T1X1 and T1M1 are the primary T1 Technical Subcommittees responsible for SONET. T1X1 deals with the digital hierarchy (shown in Figure 1–5) and synchronization. T1M1 deals with internetworking operations, administration, maintenance, and provisioning (OAM&P). Listed below are some of the most commonly cited SONET standards available from ANSI.3
- ANSI T1.105: SONET—Basic Description including Multiplex Structure, Rates and Formats
- ANSI T1.105.01: SONET—Automatic Protection Switching
- ANSI T1.105.02: SONET—Payload Mappings
- ANSI T1.105.03: SONET—Jitter at Network Interfaces
- ANSI T1.105.03a: SONET—Jitter at Network Interfaces – DS1 Supplement
- ANSI T1.105.03b: SONET—Jitter at Network Interfaces – DS3 Wander Supplement
- ANSI T1.105.04: SONET—Data Communication Channel Protocol and Architectures
- ANSI T1.105.05: SONET—Tandem Connection Maintenance
- ANSI T1.105.06: SONET—Physical Layer Specifications
- ANSI T1.105.07: SONET—Sub-STS-1 Interface Rates and For-mats Specification
- ANSI T1.105.09: SONET—Network Element Timing and Synchronization
- ANSI T1.119: SONET—OAM&P, Communications
- ANSI T1.119.01: SONET: OAM&P, Communications, and Protec-tion Switching Fragment
The Network and Services Integration Forum (NSIF)In order to assist in the SONET standards process, the Network and Services Integration Forum (NSIF) was formed to provide an open industry forum for the discussion and resolution of multiple technology integration and SONET interoperability issues.4 Its goal is to enable the delivery of services across a set of networks from different vendors and different network operators. NSIF coordinates with the appropriate standards groups, such as ANSI and the ITU-T, as required by a specific issue.
NSIF is a nonprofit membership organization comprised of equipment vendors, service providers, and other industry players who cooperatively develop end-to-end multitechnology service delivery capabilities based on industry and international standards....
1 The initial proposal stipulated a transfer rate of 50.688 Mbit/s, a 125 microsecond (µsec) signal, and a frame format of three rows by 265 columns (264 octets ×3 rows ×8 bits per octet ×8000 = 50,688,000). Later chapters explain the concepts of rows and columns.
2 Go to the ITU web site at www.itu.int for a complete list of SDH standards, along with information on purchasing the documents.
3 Go to the ANSI web site at www.ansi.org for a complete list of SONET standards along with information on purchasing the documents.
Table of Contents
|Notes for the Reader||xxi|
|What Are SONET and T1?||1|
|The Development of SONET||2|
|Role of ANSI and Key Standards Documents||5|
|The Network and Services Integration Forum (NSIF))||6|
|SONET and T1||6|
|Features of SONET and T1||8|
|Payloads and Envelopes||12|
|Optical Fiber--the Bedrock for SONET||13|
|Typical SONET Topology||15|
|Present Transport Systems and SONET||18|
|Clarification of Terms||18|
|Chapter 2||Digital Transmission Carrier Systems||22|
|Organization of Telephone Services||22|
|Types of Signaling||25|
|Connecting the User to the Telephone System||26|
|Frequency Division Multiplexing (FDM) Carrier Systems||30|
|Other Analog-to-Digital Techniques||42|
|Newer Digital Voice Schemes||49|
|The New Voice Coders||52|
|Appendix 2A||Coding and Coding Violations||53|
|Chapter 3||Timing and Synchronization in Digital Networks||57|
|Timing and Synchronization in Digital Networks||57|
|Effect of Timing Errors||60|
|The Clocking Signal||60|
|Types of Timing in Networks||61|
|Slip Operations in More Detail||67|
|Frequency Departures and Accuracies||70|
|Methods of Clock Exchange||72|
|Distribution of Timing Information with SONET and DS1 Signals||78|
|Decoupling the Clocks||79|
|Other Uses and Examples of Pointer Operations||79|
|Source Clock Frequency Recovery for Asynchronous Transfer Mode (ATM) Systems||86|
|Synchronization Status Messages and Timing Loops||87|
|Examples of Timing Supply Systems||87|
|Chapter 4||The T1 Family||93|
|T1 Line Configurations||93|
|The Digital Network||95|
|Introduction to The D Family Channel Banks||97|
|North American Asynchronous Digital Hierarchy||98|
|Digital Loop Carrier Systems||101|
|T1 Line and Trunks||103|
|D1 Channel Banks||104|
|D2 Channel Banks||109|
|D3 Channel Banks||114|
|D4 Channel Banks||115|
|Vendors' D4 Channel Banks||117|
|Other D4 Features||120|
|D5 Channel Banks||126|
|Final Thoughts on the D Channel Banks||132|
|Fractional T1 (FT1)||133|
|Dividing and Filling the T1 Channel||133|
|Compensating for Clock Differences in a T1 System||134|
|Appendix 4A||Frame Formats||137|
|Chapter 5||SONET Operations||146|
|Example of SONET Interfaces||146|
|Examples of Payload Mappings||156|
|The SONET Envelope in More Detail||157|
|SONET Equipment and Topologies||160|
|Chapter 6||Payload Mapping and Management||165|
|A Brief Review||165|
|SONET STS-1 Envelope||167|
|The SONET STS-3c Frame Structure||168|
|AT&T DDM-2000 OC-3 Shelf||169|
|Mapping and Multiplexing Operations||175|
|Rows and columns of the VTs||182|
|Construction of the Entire SPE||185|
|A Final Look At Another Mapping Operation||193|
|Chapter 7||Topologies and Configurations||195|
|Protection Switching in More Detail||195|
|Add-Drop and Cross-Connects on Ring or Point-to-Point Topologies||205|
|Provisioning SONET Machines for Add-Drop and Cross-Connect Operations||208|
|Example of Protection Switching on a Two Fiber Bidirectional Ring||215|
|Cascading the Timing on Multiple Rings||217|
|Chapter 8||Operations, Administration, and Maintenance||220|
|Need for Rigorous Testing||220|
|Categories of Tests||222|
|OAM and the SONET Layers||231|
|The SONET OAM Headers||233|
|More Information on the D Bytes||239|
|STS-3c Frames and Overhead||239|
|Maintenance Signals and Layers||241|
|Examples of OAM Operations||243|
|ATM and SONET OAM Operations||245|
|SONET and Network Management Protocols||247|
|The Network Management Model||247|
|Chapter 9||Manufacturers' and Vendors' Systems||254|
|The Major Vendors||256|
|Examples of Nortel Networks' Products||257|
|Example of OPTera Node||258|
|Examples of Fujitsu's Products||259|
|Examples of Alcatel's Products||264|
|Examples of Lucent Technologies' Products||266|
|Examples of NEC's Products||268|
|Chapter 10||The Synchronous Digital Hierarchy||269|
|SDH Systems Connecting to the United States||269|
|Comparison Of SONET and SDH||270|
|Transporting E4, H4, and DS-1 Signals||273|
|The SDH Multiplexing Hierarchy||273|
|SONET (1.544 Mbit/s) Mapping and Multiplexing Structure||274|
|SDH (2.048 Mbit/s) Mapping and Multiplexing Structure||275|
|SONET (DS1C) Mapping And Multiplexing Structure||276|
|SONET (DS-2) Mapping And Multiplexing Structure||276|
|SONET 44.736 Mbit/s, SDH 34.368 Mbit/s, and 139.264 Mbit/s Mapping and Multiplexing Structure||277|
|Three Types of Mapping for the VC-11, VC-12, or VC-2 Signals||277|
|Revised SDH Digital Hierarchy||279|
|SDH Overhead Bytes||280|
|Chapter 11||SONET and WDM, Optical Ethernet, ATM, IP, and MPLS||286|
|Introduction to WDM||287|
|Capacity of WDM||287|
|Running SONET over WDM||288|
|TDM SONET and WDM||288|
|Erbium-Doped Fiber (EDF)||289|
|Optical Cross-Connects (OXC) with WDM||292|
|Passive Optical Networks (PONs)||293|
|The "Sweet Spot"||294|
|Optical Ethernets and Ethernet PONs||295|
|ATM and SONET||296|
|IP and SONET||298|
|ATM in the SONET Envelope||298|
|IP and PPP in the SONET Envelope||299|
|ATM vs. IP over SONET||300|
|Evolution of the Optical Broadband Network||303|
|Migration to Label Switching Networks||304|
|Mapping Labels to Wavelengths||306|
|Label Switched Paths (LSPS) and Optical Switched Paths (OSPS)||307|
|Protocol Stack Possibilites||309|
|Summary and Conclusions||310|
|A New Optical Network Model||312|
|Appendix A||Transmission Media||314|
|Properties of Light and Optical Fiber||315|
|Properties of Light: Reflection and Refraction||319|
|Types of Fibers||324|
|Sources and Receivers of Optical Fiber Signals||327|
|Fiber Cable Structure||334|
When we were planning this book, our initial intent was for it to be a SONET book, with little discussion of the T1 technology. However, we decided that the book should also include T1 because many of the SONET operations are centered around T1. In addition, as we surveyed the literature on T1, we were surprised to discover that the existing books on T1 did not cover several important aspects of the subject--omissions that we have corrected in this book.
Also, we have included material on some of the original T1 channel banks. To our knowledge, this material has not appeared in any text, and the information is essential to understanding how T1 is the way it is.
In setting out to write this book, we established two goals. First, we wish to complement the overall series, and avoid undue overlapping of the subject matter of the other books. Second, we wish to explain aspects of the subject matter that have not been provided in other reference books. We found that not much tutorial literature exists on synchronization and timing, on the Building Integrated Timing Supply (BITS), on SONET configuration (crafting) operations, and some other important subjects. This information is provided in this book.