`
`The DSL SOURCEBOOK
`
`
`
`The Comprehensive Resource
`
`On Digital Subscriber Line. Technology
`
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`Uniloc's Ex. 2002, Page 1
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`

`

`'I'ABlE OF CONTENTS
`
`Foreword - welcome ...................................... [1-]
`
`Preface - About The Soureebook ............................. [1-2
`
`Chapter 1 — Introduction ................................. 1-1
`A Case for DSL ...................................... 1-1
`
`Chapter 2 — The Existing Copper Wire Infrastructure ............. 2-1
`Telephone Company Networks ........................... 2-1
`The Access Network ................................... 2-2
`
`Dedicated Tl/E1 Access Using the Local Loop Network ........ 2-4
`Private/Campus Networks ............................... 2-6
`
`Chapter 3 — DSL Basics .................................. 3-1
`Basic DSL Concepts ................................... 3-1
`Attenuation and Resulting Distance Limitations ............... 3—2
`Advanced Modulation Techniques Minimize Attenuation ........ 3-2
`Bridged Taps ........................................ 3-5
`The Effects of Crosstalk................................. 3—5
`
`Asymmetry Allows Us to Take Advantage of the Environment ..... 3-8
`The Application Switch from Vldeo to Data ................. 3-11
`Continuing Developments in DSL ........................ 3—12
`
`Chapter 4 — DSL System Components ........................ 4-1
`Adding Data to the Traditional Voice Network ................ 4—1
`DSL-Based Services and Components....................... 4-2
`A Word About Next-Generation DSLAMs ................... 4-6
`
`End—to-End Network Management Component ............... 4—7
`But This Isn’t the Whole Story ........................... 4-8
`
`Chapter 5 — Market Evolution and Deployment Realities .......... 5-1
`Market Direction ..................................... 5-1
`
`Deployment Stau'stics to Date ............................ 5-3
`Deployment Realities................................... 5—5
`The New Regulatory Environment......................... 5-7
`
`Chapter 6 — Emerging Services and Applications ................ 6—1
`An Access Technology for the New Century .................. 6-1
`Channelized T1/El Services ............................. 6-1
`IP Services — The Arrival of Internet—Based Networking ......... 6-3
`Frame Relay Services ................................... 6-6
`Frame Relay Over DSL and Service Level Management .......... 6-8
`Asynchronous Transfer Mode Services ..................... 6—10
`Private/Campus Networks .............................. 6-11
`The Next Wave: Voice Over DSL Services................... 6-16
`
`0 Copyright 2000
`Paradyne Corporation
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`

`

`Chapter 7 — Network Models .............................. 7-1
`The Need for Multiservices .............................. 7-1
`
`DSL-Based Services Reference Model ....................... 7-1
`
`Frame Relay Services Provisioning ......................... 7-3
`Nx64 Services Provisioning .............................. 7-5
`IP/LAN Services Provisioning ............................ 7-6
`IP/LAN Services Provisioning Using a Layer 2 Model .......... 7-6
`IP/LAN Services Provisioning Using a Layer 3 Model .......... 7-7
`IP/LAN Services Provisioning Using an ATM Model ........... 7-8
`An Overview of Issues for IP/LAN Services ................. 7-10
`A Word about Virtual Private Networks .................... 7-10
`
`ATM Services Provisioning ............................. 7-12
`Muln'services Architecture .............................. 7-13
`
`Chapter 8 — Sourcebook in Review .......................... 8-1
`In Closing .......................................... 8-1
`Considerations for DSL Deployment Initiatives ................ 8-1
`Common Questions and Answers about DSL ................. 8-2
`About Paradyne ...................................... 8-4
`Next Steps .......................................... 8-6
`
`DSL Sourcebook Glossary ...................................... B-l
`
`
`
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`

`

`Chapter 1
`Figure 1-1: Speed and Performance Comparison ............................ 1-1
`Figure 1—2: VoDSL Application ........................................... 1—3
`Figure 1—3: SLM—DSL (FRODSL) Wholesale Application ..................... 1—3
`Figure 1—4: End—to—End Services Delivery and Management Framework ....... 1-4
`
`Chapter 2
`Figure 2-1: Typical Voice Network ...................................... 2-1
`Figure 2—2: Traditional Repeatered Tl/El Service Provisioning .................... 2—5
`Figure 2—3: Examples of Bridged Taps .................................... 2—6
`
`Chapter 3
`Figure 3-1: Repeaterless Tl/El Replacement Model ............................. 3—3
`Figure 3-2: Tl Replacement Model Using HDSL2 ........................... 3-3
`Figure 3—3: Tl/El Replacement Model using G.shdsl ........................ 3—4
`Figure 3—4: Comparison of HDSL and T1 AMI Frequency Spectra ............... 3—4
`Figure 3-5: Line Speed and Loop Reach Comparison ......................... 3-5
`Figure 3-6: NEXT/FEXT Conceptual Model ............................... 3-6
`Figure 3-7: Typical ADSL Frequency Spectrum ............................ 3-10
`Figure 3-8: ReachDSL Conceptual Model................................. 3-13
`Figure 3—9: The Primary DSLs ......................................... 3—15
`Figure 3—10: DSL Transceiver Reference Chart ............................. 3-15
`
`Chapter 4
`Figure 4-1: Adding Data to Traditional Voice Network ........................ 4—1
`Figure 4-2: DSL-Based Services Reference Diagram ............................. 4-2
`Figure 4—3: DSIAM Features and Benefits ..................................... 4—4
`Figure 4—4: ATM Quality of Service Categories ................................. 4—6
`
`Chapter 5
`Figure 5-1: The Spiraling Need for Bandwidth .................................. 5-1
`Figure 5-2: Deployment Models, Services and Transports ......................... 5-2
`Figure 5—3: Phased Deployment of DSL—Based Services ........................... 5—3
`Figure 5—4: North American DSL Deployment as of Q2 2000 ..................... 5-4
`Figure 5-5: DSL Market Growth ............................................. 5-4
`Figure 5-6: Conceptual CLEC/ISP Backhaul Model ............................. 5-6
`
`
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`

`Chapter 6
`Figure 6-1: Tl/El Extension to the Customer Location ........................ 6-2
`Figure 6—2: Tl/El Cellular Environment ..................................... 6-2
`Figure 6—3: Emerging Web-based application matrix generated by the
`addition of audio and video media, and integration of the
`
`pull/push paradigms of content presentation ...................... 6—4
`Figure 6-4: Remote Office/Telecommuter Application .......................... 6-6
`Figure 6-5: DSL and Frame Relay ........................................... 6-7
`Figure 6—6: SLM-DSL Frame Relay Application End-to-End ..................... 6-9
`Figure 6—7: Distributed Star Topology Depicting the Campus Enviromnent ........ 6-12
`Figure 6-8: The Power of DSL in Private/Campus Network Environments ........ 6-13
`Figure 6—9: DSL in the Dormitory ......................................... 6—15
`Figure 6—10: VoDSL Network Model ......................................... 6—18
`Figure 6-11: VoDSL Market Projections ...................................... 6-18
`
`Chapter 7
`Figure 7—1: DSL—Based Services Reference Model ................................ 7—2
`Figure 72: DSL-Based Services Reference Model — Frame Relay ................... 7-3
`Figure 7-3: DSL—Based Services Reference Model — Frame Relay Management — ATM . 7-4
`
`Figure 7—4: DSL-Based Services Reference Model — Nx64 Kbps .................... 7-5
`Figure 7-5: IP/LAN Services Based Upon Layer 2 Model ......................... 7—6
`Figure 7-6: IP/LAN Services Based Upon Layer 3 Model ........................ 7-7
`Figure 7—7: IP/LAN Services Based Upon ATM Model .......................... 7—8
`Figure 7'8: DSL-Based Services Reference Model — ATM ........................ 7-12
`Figure 7-9: DSL—Based Services Reference Model — Multiservices .................. 7—13
`
`Chapter 8
`Figure 8-1: Evolution of Total Business Chart................................... 8-3
`
`
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`

`

`WELCOME...
`
`To the fast-paced, exciting (and sometimes confirsing) world of DSL (Digital Subscriber
`Line) technology. While many broadband access methods are gunning for ownership of the
`local loop, you are about to learn that DSL technology has a distinct advantage that makes
`it one of the most viable options for the delivery of high-speed data services.
`
`Unlike competing technologies, DSL eliminates the need for extensive and expensive
`infrastructure upgrades — improvements that are hard to measure in terms oftime or money.
`Where original telephone company strategies centered on the time-consuming and costly
`task of fiber installation, demand for multimegabit services has forced them to evaluate
`approaches that leverage the existing infrastructure and provide a quicker time to market.
`That is one of DSL technology’s chief advantages — the ability to transform the nearly 700
`million phone lines installed worldwide into multimegabit data pipes capable of speeding
`digital voice and data to homes and businesses.
`
`That ability has ignited the market, as telephone companies, P'ITs (Post, Telephone and
`Telegraph administrations), Interexchange Carriers (IXCs) and Competitive Local Exchange
`Carriers (CLECs) alike move to evaluate and implement this exciting new technology. Today,
`nearly every major service provider worldwide is using or trying one form ofDSL or another.
`The over-hyped information age is truly upon us as the aging copper plant continues its
`transformation into high-speed broadband networks. New, advanced applications surface
`almost daily, and expectations remain high that a host of new services — and tools to
`guarantee performance of those new services - will be launched thanks to DSL.
`
`DSL’s enormous promise has worked the telecommunications industry into a frenzy,
`seemingly overnight. As a cursory survey of the market shows, the amount of information
`and misinformation on this topic is astounding. Wading through the alphabet soup of
`acronyms and sorting through DSL fact and fiction is certainly time consuming. But DSL’s
`big bandwidth payoff is truly worth that time. That is where The DSL Saureehook - The
`Comprehensive Resource on Digital Subsmher Line Technology comes in. This Third Edition
`focuses on the state of the DSL evolution and examines emerging market requirements such
`as automated flow—through provisioning and end-to—end services delivery and management.
`These are bound to be the next great frontiers in DSL.
`
`Service providers and service users who become familiar with the growing family of DSL
`technologies can avoid pitfalls by effectively matching the appropriate DSL transport to the
`application at hand. This Sourcebook will help to level out the steep DSL learning curve and
`reduce the time it takes to select and implement the best technology for your given application.
`
`While there are many hurdles in implementing any new technology, this book will help to
`speed you on to utilizing the hottest transport to hit the local loop in years.
`
`Paradyne, a leader in the DSL equipment market, and TeleChoice, a leader in consulting
`services, are proud to bring you this concise and informative Sourcebook.
`
`Patrick Hurley
`Broadband Consultant
`
`TeleChoice, Inc.
`
`
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`

`

`PREFACE
`
`The copper wire telephone infiastructure is everywhere. Ifyou want to understand how you
`can turn existing copper into high-speed network access links, this book is for you. We wrote
`The DSL Sourcebook— The Comprehensive Resource on Digital Subscriber Line 'Ibchnology to assist
`you in making informed choices about this exciting new market. DSL technologyrs quickly
`gaining recognition and acceptance as a viable way to meet the ever-increasing demand for
`more bandwidth. As the Internet continues to evolveInto a global on--line interface supporting
`multiple media types (data, audio and video), the bandwidth demand will continue to soar.
`
`DSL-based services are not just about speed, nor about the explosive growth ofthe Internet.
`DSL-based services are about applications and opportuniu'es. DSL technology offers a win-
`win scenario for both those who provision high-speed, value-added services and for the users
`of those services, who realize dramatic cost and performance benefits.
`
`Business—critical applications require reliable performance, differentiated service guarantees,
`a highly scalable network management system to support hundreds of thousands of users
`and, of course, security. As you will see throughout this Third Edition of The DSL
`Sourcebook, DSL can meet the deployment challenges on all fi'onts. Our focus on the state
`of the DSL evolution will offer valuable insights into emerging market trends and the shift
`in design requirements to support today’s total business-class applications. The evolution
`firom yesterday’s delivery of "best effort" Internet access to today’s requirements for Wlde
`Area Network (WAN) services in support of advanced business applications requires new
`levels of service quality and service management capabilities.
`
`A wide range of residential and business-class services and applications are enhanced by DSL
`technology, which will be supported by the next-generation DSIAMs (DSL Access
`Multiplexers) to offer a full suite ofQuality ofService (Q08) capabilities. These services and
`applications include:
`
`I Traditional TI/EI Service Provisioning
`l Connectivity in Private/Campus Network
`(Multiple Dwelling/Multiple Tenant) Environments
`l IP Internet/Intranet Access Services
`
`I IP Virtual Private Networks (VPNs)
`l Frame Relay Services over DSL (FRoDSL)
`l Asynchronous Transfer Mode (A'IM) Services
`I Derived Voice Services over DSL (VoDSL)
`I Video Services
`
`Intended audiences for The DSL Sourcebook include:
`
`I Network Service Providers (NSPs) including:
`- Incumbent Local Exchange Carriers (ILECs)
`- Public Telephone Operators (PTOs)
`- Competitive Local Exchange Carriers (CLECs)
`- Independent Telephone Companies (I'I'COs)
`- Internet Service Providers (ISPs)
`- Other Network Access Providers (NAPS)
`
`
`
`f : A-2
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`l Owners ofPrivate/Campus Networks
`l Corporate Network Managers
`l Commercial Service Users
`
`l Resellers/Distributors of Wide Area Network Solutions
`l Analyst and Press Community
`
`At Paradyne, we’re in the unique position of having a rich history in digital network access,
`intemetworking, network management, and service level management (SLM). Paradyne was
`an active pioneer in the development of DSL transceiver technology. This book is a
`compilation of information on DSL and our perspective of its applicability in today’s
`marketplace. We have drawn heavily on our experience in field and market trials, worldwide
`deployments of over 10,500 DSLAMs representing over three million ports of capacity
`(through 2Q00), the DSL Forum technical and marketing committees, and numerous
`industry panel discussions in which we were invited speakers. We welcome any comments or
`questions you may have and hope you find The DSL Sourcebook a valuable reference tool for
`all your DSL initiatives.
`
`OBJECTIVES
`
`The objectives ofThe DSL Sourcebook are to:
`
`l Introduce basic DSL technology conceptsfrom a historical perspective
`I Describe how DSL technology works in the existing local loops
`l Discuss emerging services and applications that have necessitatedgreater
`bandwidth within the network and local loop
`I Detail considerations and network modelsfor DSL-based service
`deployment
`l Promote DSL-based service deployment
`
`The DSL Sourcebook contains three main sections describing essentially the WHAT, HOW
`and WHY of DSL—based service deployment.
`
`Chapters 1-4 provide the framework for the entire Sourcebook and cover the DSL basics,
`offer an understanding of the existing copper wire infrastructure, including the concept of
`private/campus networks, and offer a reference design that identifies the components
`required for DSL deployment.
`
`Chapters 5-7 delve into DSL-based services and applications. They include detailed network
`topologies and models covering multiple approaches to DSL deployment and discuss such
`issues as protocols, security, and authentication.
`
`Chapter 8 provides answers to some common questions about DSL-based services and will
`serve as a usefiil planning reference.
`
`QUICK-SCAN 'I'OOIS
`Throughout the Sourcebook, you will find two quick-scan tools to help you navigate easily
`through the information.
`
`I Highly technical sections are ojj‘i'et in rules, targeting the reader who
`already has a relatively high understanding ofDSL.
`I Chapter Summaries are provided at the end of most chapters.
`
`
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`

`

`Chapter 1
`
`INTRODUCTION
`
`A CASE FOR DSL
`
`Digital subscriber line technology is a copper-loop transmission technology that solves the
`bottleneck problem often associated with the last mile between network service providers and
`the users of those network services.
`
`DSL technology achieves broadband speeds over the most universal network medium in the
`world: ordinary phone wire.
`
`While DSL technology offers dramatic speed improvements (up to 8+ Mbps) compared to
`other network access methods, the real strength ofDSL-based services lies in the opportunities
`driven by:
`
`I Multimedia applications required by today’: network users
`I Perfbrmance and reliability
`l Economic:
`
`As shown below in a sample comparison diagram, DSL-based services provide performance
`advantages for network service users compared to other network access methods. In addition,
`DSL-based services extend these operational improvements for both public and private
`(campus) network operators. The concepts below will be covered in greater detail in Chapter
`7, Network Models. However, for the purpose of this comparison, the Service User (endpoint
`location) gains access to an NSP network through a Network Access Provider network.
`
`Network Service Provider
`
`Corporate
`Network
`
`
`
`
`
`
`
`
`Frame Relay
`Network
`
`Network Access Provider
`- CLEC
`- nco
`- RBOC
`- PTT
`- IXC
`
`Service User
`
`FIGURE I-I
`Speed and
`Performance
`
`Comparison
`
`User CPE
`
`T1/E1 DSUICSU
`or DSL Router
`1 544/2048 Mbps
`
`
`
`Service
`User CPE
`
`W
`2
`W/
`DSL ModemIRouter
`Service
`8* Mbps
`
`
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`

`Imagine having the ability to:
`
`I foer enhanced new services that would be valued by your customers
`I Flexibly offer multiple services with differing tiers ofbandwidth,
`performanceguarantees, and pricing
`I Reliably and easily deliver and manage business-critical applications
`I Utilize new services to perform your work at speeds you once only dreamed
`possible
`
`One of the most compelling benefits of DSL technology is that it allows the NSP and the
`service user to take full advantage of existing infrastructures, Layer two and Layer three
`protocols (such as flame relay, ATM and IP), and the reliable network services they have
`already come to trust. In an evolving market such as DSL, support for multiple service types
`on a single platform offers an important investment protection. The evolving DSL market
`includes both packet and cell-based services such as ATM, frame relay, and IP as well as bit
`synchronous channelized services. Next-generation DSLAM architectures that support
`multiple services, technologies and transports ensure that the infrastructure investment
`already in place remains protected.
`
`DSL can easily support advanced business-class services like derived Voice over DSL
`(VoDSL) and new variations of proven and well understood technologies such as Frame
`Relay over DSL (FRoDSL), with the newest generations of DSL equipment offering
`end-to-end service level management (SLM). To keep things simple, in our discussion of
`business-class DSL applications, we will group everything under one new acronym:
`SLM-DSL.
`
`One could argue that without service level management, there is no real businessclass DSL,
`because business customers require differentiated services and are willing to pay a premium
`for performance guarantees on their mission—critical applications.
`
`For example:
`
`VoDSL provides multi-line (typically 4-12 phone lines) voice capability over a DSL
`connection using low-latency ATM virtual circuits. Voice traffic is routed to a VoDSL
`gateway and then onto the PSTN (Public Switched Telephone Network). This approach
`offers DSL customers the cost and convenience advantages of using a single service provider
`for both data and voice needs, without the need to have additional phone lines provisioned.
`A single copper pair can meet both the voice and data needs of many small- or medium -size
`businesses. How? DSL networks are packet—based, allowing VoDSL solutions to use the
`bandwidth of a DSL connection dynamically. This means that voice calls only need to
`consume bandwidth when a call is active, and due to the low bandwidth utilization ofvoice
`services relative to data services, several voice calls can traverse a DSL connection
`simultaneously (see Figure 1-2).
`
`
`
`-' : 1-2
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`

`

`FIGURE l-2
`VoDSL
`
`Application
`
`
`
`The business customer can’t lose. The savings realized more than offset the premium they’ll
`pay for the derived voice channels and the Real-Time Variable Bit Rate (rt-VBR) QoS
`classification they’ll want to ensure toll-quality performance.
`
`FRoDSL, when combined with an end-to-end service level management system, fulfills both
`critical elements of the value proposition:
`
`LEconomical accent to the frame relay network
`2.Equivulent or better service performanceguarantee:
`
`W
`Subsaber‘s
`_
`W W?”
`‘
`
`‘~.
`
`\
`
`--------------
`
`IXC NOC
`
`/
`
`W533
`_
`FRoDSL)
`0168816
`Application
`
` ATM Access
`Network
`
`Network
`
`To IXC
`Frame Relay
`
`In short, FRoDSL allows business customers to do what they’ve already been doing for quite
`some time — only at a lower cost. FRoDSL will significantly lower the cost of provisioning
`frame relay services to a customer by reducing the cost of the local access portion of the
`network. Typically, fi'ame relay customers utilizing private line access to the network spend
`up to 38 percent oftheir total costs just on this access. Using a lower-cost DSL access, along
`with an end-to-end service level management system that can ensure the same quality of
`service as private lines, can bring considerable cost savings to the provisioning offrame relay,
`particularly for the frame relay service providers who have been forced to lease the access
`component from Local Exchange Carriers (LECs).
`
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`

`With the rapid changes in the overall networking environment, one winning strategy for
`DSL-based service deployment is to build in the flexibility needed to support a range of
`applications. Chapter 8, Sourcebook in Review, includes a comprehensive checklist of
`considerations for DSL deployment planning. Some examples of key criteria for a flexible
`DSL-based system include:
`
`I Ability ofthe solution to support multiple service types on a single
`platform
`I Scalability to supportfrom a few users to hundreds of thousands of users
`I Ability of the solution to provide reliable end-to-end network
`management in support of mission-critical applications
`I Ease ofprovisioning and integration with higher-layer Operating
`Support System (OSS) applications
`I Digital loop carrier (DLC) support
`
`The figure below shows the end-to-end services delivery and management framework. Best-
`in-class solutions need to consider interoperability at the Service Transport Level not only
`for third-party CPE, but for voice gateways, subscriber management systems and so forth.
`In addition, these elements must be easily integrated into the Management Framework — the
`higher-layer 088 applications.
`
`Management —_ swam
`Framework
`
`.
`
`FIGURE I4
`End-to-End
`
`Services Delivery
`and Management
`Framework
`
`Network
`
`Transport
`
`Service
`
`After several years of commercial deployment of both symmenic and asymmetric high-speed
`applications, NSPs have recognized that DSL technology is not really the I'next generation"
`of digital network access, but rather the "now generation" of digital network access.
`
`
`
`#:1-4
`
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`

`

`Chapter 2
`
`THE EXISTING COPPER WIRE
`INFRASTRUCTURE
`
`TELEPHONE COMPANY NETWORKS
`
`As noted in the introduction, DSL products bring entirely new service capabilities to the
`existing copper wire local access network. In order to understand the opportunities and
`challenges relating to the deployment of DSL-based services, it is useful to review the
`existing infi'astructure of the telephone network.
`
`The telephone networks currently in place within ILECs and PTOs represent a huge capital
`investment that has taken place over the last 120 years. This structure was primarily designed
`for voice services. Over time, telephone networks have undergone numerous modernization
`and infrastructure upgrades to take advantage of advancements in transmission and switching
`technologies. In particular, high-capacity, fiber optic transmission facilities currently exist in
`nearly every telephone company backbone network worldwide. The use of fiber optics
`improved the quality of the services, increased the capacity of traffic that can be supported
`over the backbone network, and reduced operational expenses for network operators.
`
`As a result, high-capacity service capabilities exist between telephone company offices.
`However, the situation is very different when you look at the local loop access network, the
`last leg, which connects end service users to the telephone company backbone networks. Any
`discussion of the local loop and high-speed data services must start with an examination of
`the topology of the existing voice services physical network.
`
`T—1 IE1 or Fber
`
`FIGURE 2"
`T ical Voice
`etwork
`
`CO -
`Central Office
`RT - Remote
`Terminal
`DLC - Digital
`Loo Carrier
`MD - Main
`Distribution Frame
`
`
`
`and DLC RTs
`
`Figure 2-1 represents a typical ILEC/PTO telephone network. Several central offices (COs)
`are depicted as being outfitted with telephone switches and transmission equipment, as well
`as digital loop carrier remote terminals (RTs).
`
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`

`From the home or office, twisted-pair copper wire local loops interconnect to the telephone
`switch through a main distribution frame (MDF). The MDF is the central point at which all
`local loops terminate in the CO.
`
`Central offices are interconnected through an inter-C0 network. This network consists of
`Digital Access and Cross-connect Systems (DACS) and T/E—carrier transmission equipment.
`Inter-CO networks have been upgraded to the latest in fiber optic ring technology (SONET
`or SDH).
`
`'I'IIE ACCESS NETWORK
`
`DSL is really an access technology, and the associated DSL equipment is deployed in the local
`access network. Therefore, it is very important to have a clear understanding of the local
`access network. Let’s take a closer look.
`
`The access network consists of the local loops and associated equipment that connects the
`service user location to the central office. This network typically consists of cable bundles
`carrying thousands of twisted-wire pairs to feeder distribution interfaces (FDIs). FDIs are
`points where dedicated cable is extended out to the individual service users.
`
`Some service users are located a long way from the central office and require a very long local
`loop. One problem with very long loops is that the elecn‘ical signals dissipate energy as they
`traverse the loop, making the signals weak. In a very simplistic way, it is like a radio signal.
`As you go farther away from the transmitter, the weaker the signal gets, resulting in lower
`signal-to-noise levels.
`
`Telephone companies found two primary ways to deal with long loops:
`
`1. Use loading coils to modify the electrical characteristics of the local loop,
`allowing better quality voice-frequency transmission over extended
`distances (typicallygreater than 1 8, 000 feet). In this extended-distance
`scenario, loading coils are placed every 6, 000 feet on the line.
`
`We will learn later that loading coils are not compatible with the
`higher frequency attributes of DSL transmissions and they must
`be removed before DSL-based services can be provisioned. The
`use of loading coils varies by telephone company and typically
`ranges from virtually none to as high as 20 percent of the local
`loops within a given telephone company’s access network.
`
`2.Set up remote terminals where the signals could he terminated at an
`intermediate point, aggregated and hackhauled to the central office, which
`houses the switching equipment and high-capacity transmission equipment
`or, in other cases, to a serving wire center (S WC) that does not have
`switching equipment but does have the transmission equipment that
`connects to other central offices. The hackhaul to the C0 or SWC via
`TI/EI circuits may be based on copper orfiber-based technologies.
`
`
`
`f: 2-2
`
`Uniloc v. Facebook, |PR2017-01524
`Uniloc‘s Ex. 2002, Page 14
`
`

`

`While initial telephone networks terminated the copper wire
`loops directly in the CO,
`the combination of maintenance
`challenges associated with long loops and issues associated with
`provisioning an increasing number of loops created the need for
`architectural changes in the local access network. Unfortunately,
`the same fiber optics that could be justified from a CO connecting
`thousands of service users to other COs are not yet cost justified
`for individual users. Therefore, a compromise solution was to
`terminate loops at intermediate points using DLCs that are closer
`to the service users. These intermediate points are referred to as
`remote terminals.
`
`One advantage of terminating the loops at the DLC remote
`terminal is that it reduces the effective length of the copper line,
`thus improving the reliability of the service. An additional benefit
`is that Plain Old Telephone Services (POTS) can be multiplexed
`into a higher-speed Tl
`(primarily a North American and
`Japanese standard supporting up to 24 digitized voice channels
`at 64 Kbps each) or El (an international standard used primarily
`by the rest of the world supporting up to 30 digitized voice
`channels) format for transmission to a central office over a single
`fiber optic or four-wire circuit. As we will see later, while the RT
`architecture solves many problems for POTS,
`it
`introduces
`complexities relative to the provisioning of DSl.-based services.
`
`DSl. transmissions can only be supported over contiguous copper
`wire loops. Therefore, for a DSL-based service connected to an
`RT, the DSl. portion must terminate at the RT, where the DSl.
`transport is then converted to a format compatible with the DLC.
`The use of DLCs varies by telephone company and typically
`ranges from almost none to as high as 30 percent of the local
`loops within a given telephone company’s access network.
`
`
`Current projections estimate that nearly 700 million copper wire access lines connect homes
`and business customers to the Public Switched Telephone Network (PSTN) worldwide.
`More than 95 percent of the local access loops consist of a single-pair (two-wire circuit)
`twisted wire supporu'ng POTS.
`
`By definition, POTS is designed to carry a voice conversation, which for adequate fidelity
`requires the lines to handle frequencies from 0 Hz (hertz) up to about 3,400 Hz (1 Hz = 1
`cycle per second). This narrowband service has historically supported only voice calls or
`analog modem transmissions at speeds commonly ranging from 9.6 to 33.6 kilobits per
`seconds (Kbps), and more recently approaching the 56 Kbps range.
`
`On a global scale, a very small percentage of the PSTN connections are provisioned with
`Basic Rate Interface (BRI) Integrated Services Digital Network (ISDN) services. With Basic
`Rate ISDN, customers have the option of either two B-channels (Bearer channels) for one
`voice and one data, two voice, or two data (64 Kbps each); or 128 Kbps by combining both
`B—channels for data service. Basic Rate ISDN also provides a 16 Kbps D-channel (Data
`