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1 Basic Telecommunications: Student Guide PCL02-CNBT00-PR-212! Version 6.0P

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3 The CCNT Certificate Program The convergence of telecommunications and data networks is happening at a rapid pace, and IT professionals are increasingly expected to understand both voice and data technologies. In response to this need, the Certified in Convergent Network Technologies (CCNT) program has been developed. CCNT is the only vendor-neutral, industry-standard, training and testing program in core convergence technologies sponsored by the TIA (Telecommunications Industry Association). To obtain this industry-valued credential, you must pass six (6) competency tests: Basic Telecommunications Basic Data Communications Computer-Telephony Integration (CTI) Essentials Local Area Networks (LANs) Broadband Technologies Voice over IP (VoIP) Essentials ComputerPREP offers flexible learning solutions mapped to these competencies, including instructor-led training, computer-based training (CBT), and Web-based training (WBT). Benefits of the CCNT Certificate The CCNT certificate is geared toward anyone who wants to remain current in the data and telecommunications industries, including network administrators and engineers; telecommunications sales professionals, engineers and consultants; and telecommunications and data communications instructors. CCNT is also well suited to anyone taking advanced vendor-neutral or product-specific certificate programs. With the CCNT certificate, you can prove competency in data and telecommunications technologies, enhance career potential, and build confidence. Because the CCNT certificate program develops and certifies work-ready skills, it can be used as an employee-screening tool. It also provides an industry-valued, competency-based credential that is sponsored by the TIA. Preparing for the CCNT Exam The CCNT exam consists of six (6) separate competency tests. These tests can be taken independently of one another, allowing you to prepare for each test individually. The CCNT certificate program requires that you become familiar with all six (6) competency areas. This course is designed to provide the necessary competency skills required to pass the corresponding module of the CCNT exam.

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5 Basic Telecommunications: Student Guide Published by ComputerPREP, Inc. Phoenix, Arizona PCL02-CNBT00-PR-212 Version 6.0P

6 Basic Telecommunications Developers Meagan McLaughlin and Brent Capriotti Editors Jill McKenna and David Oberman Publishers Joseph Flannery and Joseph A. Servia Project Managers Dave De Ponte and Todd Hopkins TRADEMARKS ComputerPREP is a registered trademark of ComputerPREP, Inc. in the United States and other countries. Microsoft, Microsoft Internet Explorer logo, and Windows are either registered trademarks or trademarks of the Microsoft Corporation in the United States and/or other countries. All other product names and services identified throughout this book are trademarks or registered trademarks of their respective companies. They are used throughout this book in editorial fashion only. No such use, or the use of any trade name, is intended to convey endorsement or other affiliation with the book. Copyrights of any screen captures in this book are the property of the software s manufacturer. DISCLAIMER ComputerPREP, Inc. makes a sincere effort to ensure the accuracy of the material described herein; however, ComputerPREP, Inc. makes no warranty, express or implied, with respect to the quality, correctness, reliability, currentness, accuracy, or freedom from error of this document or the products it describes. ComputerPREP, Inc. makes no representation or warranty with respect to the contents hereof and specifically disclaims any implied warranties of fitness for any particular purpose. ComputerPREP, Inc. disclaims all liability for any direct, indirect, incidental, consequential, special, or exemplary damages resulting from the use of the information in this document or from the use of any products described in this document. Mention of any product does not constitute an endorsement by ComputerPREP, Inc. of that product. Data used in examples and sample data files are intended to be fictional. Any resemblance to real persons or companies is entirely coincidental. ComputerPREP makes every effort to ensure the accuracy of URLs referenced in all our materials, but we can not guarantee that all will be available throughout the life of the course. When this manual/disk was published, all URLs were checked for accuracy and completeness. However, due to the ever-changing nature of the Internet, some URLs may no longer be available or may have been re-directed. COPYRIGHT NOTICE This Guide is copyrighted and all rights are reserved by ComputerPREP, Inc. No part of this publication may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language or computer language, in any form or by any means, electronic, mechanical, magnetic, optical, chemical, manual, or otherwise, without the prior written permission of ComputerPREP, Inc., 410 North 44th Street, Suite 600, Phoenix, Arizona Copyright 2003 by ComputerPREP, Inc. All Rights Reserved ISBN: X

7 v Table of Contents Course Description...xiii ComputerPREP Courseware... xiv Course Objectives...xv Classroom Setup... xviii Lesson 1: Overview Pre-Assessment Questions The Telecommunications Industry Terms and Technology Regulation and Public Policy Technical Platform The International Perspective Lesson Summary Lesson 1 Review Lesson 2: Customer Premise Equipment (CPE) Pre-Assessment Questions Station Sets Key Systems Private Branch Exchange (PBX) Centrex Virtual PBX Lesson Summary Lesson 2 Review Lesson 3: Services Pre-Assessment Questions Introduction Service Basics Line and Trunk Features Dedicated Services Service Providers Specialized Services Lesson Summary Lesson 3 Review Lesson 4: Analog Concepts Pre-Assessment Questions The Network The Voice Signal Transmission Variables Multiplexing FDM Lesson Summary Lesson 4 Review Lesson 5: Digital Concepts Pre-Assessment Questions Digital Signals Advantages of Digital Technology Digital Transmission Pulse Code Modulation Digital Voice Transport Optical Standards

8 vi Digital Loop Carriers Lesson Summary Lesson 5 Review Lesson 6: Networks Pre-Assessment Questions Telecommunications Networks The Flexibility of Computer Technology Current Network Structure The Exchange/Central Office Cellular Networks Internet Telephony Lesson Summary Lesson 6 Review Lesson 7: Transmission Pre-Assessment Questions A Simple Transmission Network What Are the Transmission Media? Two-Wire Analog Media Multicircuit Media and Systems Lesson Summary Lesson 7 Review Lesson 8: Signaling Pre-Assessment Questions Basic Types of Signaling Supervisory Signaling Start-Dial Signals Address Signaling Incoming Call Indication Call Progress Tones and Miscellaneous Signals Common Channel Signaling Signaling System 7 (SS7) Identifying the Signaling Interface Lesson Summary Lesson 8 Review Lesson 9: Switching Pre-Assessment Questions Introduction to Switching Analog Switches Digital Switches Time-Division Switching Space-Division Switching CO Digital Switches Optical Signal Switching Lesson Summary Lesson 9 Review Lesson 10: Application Analysis Pre-Assessment Questions Determination of Applications Determination of Quantities Lesson Summary

9 vii Lesson 10 Review Glossary...Glossary-1 Index... Index-1 Supplemental CD-ROM Contents... Supplemental CD-ROM Contents-1 List of Figures Figure 1-1: IP phones, cable modem, and cell phones support voice, fax, and data Figure 1-2: Growth in telephony since Figure 1-3: LECs share telecommunication markets with competitors Figure 1-4: Telecommunications revenue distribution over time Figure 1-5: Demarc is connection point between CPE and PSTN Figure 1-6: Demarc is often housed in equipment room Figure 1-7: Wire center houses switch that is connected to all other switches Figure 1-8: Access connects CPE to network Figure 1-9: The FCC regulates interstate communications Figure 1-10: Standards organizations Figure 1-11: Current state of telecommunications industry regulation Figure 1-12: Telecommunications industry monopolization and demonopolization Figure 1-13: Telecommunications industry regulation before 1980s Figure 1-14: Telecommunications industry regulation s (United States) Figure 1-15: Telecommunications industry regulation 2000s Figure 1-16: Early development of telecommunications technology Figure 1-17: Stored program control switch reduced telephony costs Figure 1-18: Mobile telephones and Web browsers changed telecommunications Figure 2-1: Station sets are made in many varieties Figure 2-2: Station set functions Figure 2-3: Single line and multiline analog sets Figure 2-4: Analog signaling techniques Figure 2-5: Touchtone signaling Figure 2-6: Supervisory signaling Figure 2-7: A digital set has more than one pair of wires Figure 2-8: Digital sets use message-oriented and stimulus signaling Figure 2-9: Advanced station set features Figure 2-10: Wireless sets communicate through antennas Figure 2-11: Key systems allow users to share lines Figure 2-12: Key system inbound features Figure 2-13: DNIS identifies the number originally dialed by the caller Figure 2-14: Key system outbound features Figure 2-15: Intercom calling features Figure 2-16: Key systems versus PBXs Figure 2-17: Outbound call functionality of PBX systems Figure 2-18: Inbound call functionality of PBX systems Figure 2-19: Intra-business features of PBX systems Figure 2-20: OPX and DISA are PBX features used by off-premise employees Figure 2-21: Automatic call distributor (ACD) Figure 2-22: PBX system with ACD Figure 2-23: PBX administrative and maintenance capabilities Figure 2-24: Systems associated with PBX systems Figure 2-25: Centrex is provided by an LEC or IXC Figure 3-1: Types of telecommunications services Figure 3-2: Call billing regions

10 viii Figure 3-3: Local call billing Figure 3-4: Billing boundaries Figure 3-5: San Francisco local calling area Figure 3-6: Local calling area for Sunnyvale Figure 3-7: California LATA map Figure 3-8: Long-distance call billing Figure 3-9: Internal carrier billing Figure 3-10: Analog business lines Figure 3-11: Key systems use analog lines to connect to network Figure 3-12: 2-way combo trunks can be analog or digital Figure 3-13: 2-way combo and outdial trunks Figure 3-14: DID trunks allow direct calls to receiving station Figure 3-15: Dedicated access using T1 system Figure 3-16: 2-way DID using dedicated access Figure 3-17: 2-way DID with long-distance service Figure 3-18: Integrated T1 reduces the number of trunks required Figure 3-19: CPE features Figure 3-20: Sequential hunting Figure 3-21: Circular hunting Figure 3-22: Remote call forwarding Figure 3-23: Features available on trunks Figure 3-24: Non-switched services are dedicated services Figure 3-25: Pricing depends on service type, bandwidth and distance Figure 3-26: Many small businesses use traditional switched access Figure 3-27: PBXs use dedicated access Figure 3-28: Integrated communications providers can provide all services Figure 3-29: Matrix of services available from providers Figure 3-30: Specialized services Figure 3-31: ISDN and switched 56 connections Figure 3-32: Service provider application project Figure 4-1: Switching refers to the routing of a call Figure 4-2: Signaling involves call setup information Figure 4-3: Transmission transmits voice and data point-to-point Figure 4-4: Sound is produced by moving air Figure 4-5: Transduction is the conversion of energy Figure 4-6: An analog signal can be charted as a sine wave Figure 4-7: Frequency is the number of cycles completed in a second Figure 4-8: A string can carry sound Figure 4-9: The effect of attenuation on frequency Figure 4-10: The effect of attenuation on frequency in loaded cable Figure 4-11: Electrical noise is caused by nearby electrical interference Figure 4-12: Full-duplex transmission Figure 4-13: Open wire line, radio and coax carry multiplexed signals Figure 4-14: Frequency-division multiplexing (FDM) Figure 4-15: Modulation Figure 4-16: Signal modulation Figure 4-17: The bandpass filter removes the extra sideband and carrier Figure 4-18: Channel bank output Figure 4-19: Channel capacity of L carriers Figure 4-20: Factors affecting noise in analog systems Figure 5-1: Digital signals versus analog signals Figure 5-2: Analog signals are electrical energy Figure 5-3: Digital signals represent the original signal indirectly

11 ix Figure 5-4: Analog bandwidth is measured in frequency range Figure 5-5: Digital bandwidth is measured in bits per second Figure 5-6: Regenerators restore attenuated digital signals Figure 5-7: Noise is amplified with analog signal Figure 5-8: Digital signals are resistant to crosstalk Figure 5-9: Digital circuitry has become more affordable Figure 5-10: Backward compatibility requires signal conversion Figure 5-11: Codecs perform analog/digital conversions Figure 5-12: Codecs are found in many types of equipment Figure 5-13: Codecs use many methods of analog-to-digital conversion Figure 5-14: Pulse amplitude modulation samples 8,000 times per second Figure 5-15: PAM's output series of pulses Figure 5-16: DPCM focuses on difference between samples Figure 5-17: ADPCM addresses DPCM's weaknesses Figure 5-18: Delta modulation records direction of change in samples Figure 5-19: DS0 is standard for single PCM voice channel Figure 5-20: DS1 frame is composed of 24 DS0s and one framing bit Figure 5-21: Channelized versus non-channelized T Figure 5-22: DS0 digital hierarchy for electronic media Figure 5-23: Optical transmission includes source, medium and receiver Figure 5-24: Optical carrier standards Figure 5-25: Twisted pair is used for distances up to 15,000 feet from CO Figure 6-1: IXC POPs in rural areas carry signals to remote switches Figure 6-2: Metropolitan areas require complex networks Figure 6-3: Complex networks offer multiple management schemes Figure 6-4: Missouri LATA map Figure 6-5: LATAs contain many COs and several exchanges Figure 6-6: IXC POPs can provide IXC access within LATA Figure 6-7: Rural LATA using wire center Figure 6-8: IXC A has direct connection with all ILECs Figure 6-9: IXC B has connection with ILECs it uses frequently Figure 6-10: CLEC A and CLEC B are both directly connected to IXC C Figure 6-11: Missouri LATA map and area codes Figure 6-12: Metropolitan wire center Figure 6-13: CLEC circuit switch with digital crossconnect and multiplexers Figure 6-14: Mesh configuration used in areas of heavy traffic Figure 6-15: Star configuration is used in less dense areas Figure 6-16: Cellular service is provided within MSAs Figure 6-17: MTSOs route calls to best site to maximize signal strength Figure 6-18: Roaming occurs when cell phone is outside its home area Figure 6-19: Generations of cellular technology Figure 6-20: VoIP is Internet transmission of voice and video Figure 6-21: PSTN versus Internet Figure 6-22: Gateways are required for calls between PCs and phones Figure 6-23: VoIP using private Internet or intranet Figure 6-24: Cable providers now offer voice services Figure 7-1: Typical analog phone call Figure 7-2: All calls are transmitted to CO for switching Figure 7-3: Calls are transmitted over trunk to IXC POP Figure 7-4: Call may be transmitted to another CO Figure 7-5: Intra-office calls stay within same wire center Figure 7-6: Telephone poles and cable were common transmission media Figure 7-7: Types of transmission media

12 x Figure 7-8: Full-duplex transmission Figure 7-9: Carrier system used to connect PBX with CO Figure 7-10: T carrier systems do not require digital/analog conversion Figure 7-11: Interoffice trunks are carrier systems Figure 7-12: Many different access and transport options exist Figure 7-13: Types of access systems Figure 7-14: Types of transport systems Figure 7-15: Most analog residential circuits are two-wire circuits Figure 7-16: Every residence must be connected to access network Figure 7-17: DSL can use data-over-voice or pure data Figure 7-18: Carriers use smart jack to terminate T1 circuit Figure 7-19: T1 carrier transmits 24 8-bit DS0 signals and one framing bit Figure 7-20: D4 superframe framing bit pattern Figure 7-21: Extended superframe (ESF) requires 24 frames Figure 7-22: T1 can be multiplexed Figure 7-23: Electrical carrier standards Figure 7-24: SONET optical carrier standards Figure 7-25: One OC1 carries 28 T1s Figure 7-26: Add/drop multiplexers do not require multiplexing Figure 7-27: Digital crossconnect system (DCS) mapping and test access ports Figure 7-28: SONET management includes bits for section, line and path Figure 7-29: Alternate mark inversion (AMI) Figure 7-30: 2-binary, 1 quaternary (2B1Q) Figure 7-31: Quadrature amplitude modulation (QAM) Figure 8-1: Subscriber signaling, or line-side signaling Figure 8-2: Interswitch signaling, or trunk-side signaling Figure 8-3: Subscriber signaling uses DC signaling Figure 8-4: In-band signaling Figure 8-5: Out-of-band signaling Figure 8-6: Common channel signaling Figure 8-7: Types of supervisory signaling in UNI Figure 8-8: Loop-reverse battery supervision Figure 8-9: Out-of-band supervision used with ISDN or CCS lines Figure 8-10: Start dial signaling Figure 8-11: U.S. address signaling Figure 8-12: DTMF, rotary dial and MF signaling Figure 8-13: Incoming call signaling varies based on trunk type Figure 8-14: In-band call signals Figure 8-15: Call setup and transmission using in-band signaling Figure 8-16: CCS network structure Figure 8-17: Many different links are used between CCS components Figure 8-18: Switches and signaling make SS7 services possible Figure 8-19: SS7 signaling for direct long-distance call Figure 8-20: Redirected call using SS7 signaling Figure 8-21: Calling name retrieval in SS7 network Figure 8-22: Complete call using in-band signaling Figure 8-23: Complete call using out-of-band signaling Figure 8-24: Loop-start signaling is provided from the line side of the switch Figure 8-25: DID connections are on trunk side of telco switch Figure 8-26: PBXs connected with tie trunks Figure 8-27: ISDN PRI has more powerful signal than ISDN BRI Figure 8-28: SS7 is used between switches Figure 9-1: Concentration, distribution and expansion are switching functions

13 xi Figure 9-2: Switching functions Figure 9-3: Operations, administration, maintenance and provisioning Figure 9-4: Switching structure Figure 9-5: Step-by-step switching Figure 9-6: Crosspoint switches several individual switches arranged in matrix Figure 9-7: Time-division multiplexing (TDM) Figure 9-8: Time-division switching rearranges time slots within frames Figure 9-9: Reordering time slots requires control logic, buffer and counter Figure 9-10: Control logic determines unloading order of time slots Figure 9-11: Time-division switching is useful when inputs and outputs are equal Figure 9-12: Space-division switching is useful when inputs and outputs differ Figure 9-13: Space-division switching moves DS0s or DS1s Figure 9-14: Logic gates are closed at intersecting points Figure 9-15: Time-division versus space-division switching Figure 9-16: Switches have control elements and switching fabric Figure 9-17: Each space-switching matrix is one stage Figure 9-18: Time-space-time (TST) switch Figure 9-19: Switch configuration using time slot Figure 10-1: Planning Figure 10-2: Business needs Figure 10-3: Discovery process interviews Figure 10-4: Considerations for discovery process Figure 10-5: Interview goals Figure 10-6: Discussion areas for discovery process Figure 10-7: System administration concerns Figure 10-8: Information access factors Figure 10-9: Direct inward dialing (DID) Figure 10-10: Inbound access to fax Figure 10-11: Internet access considerations Figure 10-12: Conferencing needs Figure 10-13: Connectivity needs Figure 10-14: Benefits of similar systems Figure 10-15: Remote workers' needs Figure 10-16: Telecommuters' needs Figure 10-17: Security concerns Figure 10-18: Business continuity Figure 10-19: Protection of information Figure 10-20: Call center considerations Figure 10-21: Information flow matrix Figure 10-22: Voice circuit needs Figure 10-23: Busy hour variations Figure 10-24: Service model Figure 10-25: Service criteria List of Tables Table 1-1: Telephony growth since Table 1-2: Additional telephony authorities Table 3-1: Sunnyvale local calling areas Table 3-2: Telephone code changes Table 3-3: Country codes Table 3-4: First four levels of DSH and T-carrier equivalents Table 3-5: E-carrier speeds

14 xii Table 5-1: Predictive codec types Table 5-2: ANSI-mandated rates for SONET Table 5-3: ITU-specified rates for SDH Table 8-1: Common signaling interfaces Table 9-1: TST switch calls

15 xiii Course Description Welcome to Basic Telecommunications. This course will help you prepare for the Certified in Convergent Network Technologies (CCNT) exam, a program sponsored by the TIA (Telecommunications Industry Association). This course is aimed at preparation and review for the Basic Telecommunications module of the CCNT exam, as well as professional development for IT professionals. It is designed to be used in a lecture-based classroom setting. Basic Telecommunications introduces the concepts of analog and digital technologies, networks, business communications systems, signaling, and switching. This course has ten lessons, and each lesson covers several topics. Following are the ten lessons of the Basic Telecommunications course, along with the topics covered in each lesson. Topics Covered Overview The Telecommunications Industry Terms and Technology Regulation and Public Policy Technical Platform The International Perspective Customer Premise Equipment (CPE) Station Sets Key Systems Private Branch Exchange Centrex Virtual PBX Services Service Basics Line and Trunk Features Dedicated Services Service Providers Specialized Services Analog Concepts The Network The Voice Signal Transmission Variables Multiplexing FDM Digital Concepts Digital Signals Advantages of Digital Technology Digital Transmission Pulse Code Modulation Digital Voice Transport Optical Standards Digital Loop Carriers Networks Telecommunications Networks The Flexibility of Computer Technology Current Network Structure The Exchange/Central Office Cellular Networks Internet Telephony

16 xiv Transmission A Simple Transmission Network Signaling Basic Types of Signaling Switching Introduction to Switching What Are the Transmission Media? Two-Wire Analog Media Multicircuit Media and Systems Supervisory Signaling Start-Dial Signals Address Signaling Incoming Call Indication Call Progress Tones and Miscellaneous Signals Common Channel Signaling Signaling System 7 Identifying the Signaling Interface ComputerPREP Courseware Analog Switches Digital Switches Time-Division Switching Space-Division Switching CO Digital Switches Optical Signal Switching Application Analysis Determination of Applications Determination of Quantities This learning guide was developed for instructor-led training and will assist you during class. Along with comprehensive instructional text and objectives checklists, this learning guide also includes pre-assessment questions, tech terms, and lesson summaries and reviews. Each lesson in this course follows a regular structure, along with graphical cues to illustrate important terms and concepts. The structure of a typical module includes: Pre-Assessment Questions Each lesson includes pre-assessment questions to test student's understanding of the key concepts presented in the lesson. Objectives Each lesson includes a list of objectives to set the stage for the rest of the lesson. Tech Terms All terms that are defined throughout the text appear in bold font. Lesson Summary The Lesson Summaries at the end of each lesson include: an Application Project to extend learning, a Skills Review of key concepts and objectives presented in the lesson, and Lesson Review Questions designed to test understanding. Glossary The Glossary contains a list of key terms defined throughout the course, and can be used for self-study once the course has been completed. Table of Contents and Index The Table of Contents appears at the beginning of the book, and the Index appears at the end. These can also be used to review key areas.

17 xv Course Objectives Define telecommunications. Identify the different types of network providers and their functions. Describe today's telecommunications environment. Describe how today's environment was shaped by the history of legal and business practices. Identify two key objectives of telecommunications systems. Describe the features and functions of station sets. Describe how today's environment was shaped by technological evolution. Describe the status of international telecommunications connectivity. Describe station sets and station set functions. Describe signaling methods used by station sets. Distinguish among key systems, PBX systems and Centrex. Discuss system features and their advantages. Discuss a breakdown of services into categories. Identify local services applicable to station sets, key systems, PBXs, and other customerpremises equipment. Identify the toll and long distance choices available and billing options. Discuss differences in options available from traditional and new carriers. Describe specialized services available from carriers. Identify the network processes that are common to analog and digital transmissions. Describe the characteristics of the analog voice signal. Describe the key transmission variables for the analog signal. Describe the most common method of multiplexing in analog transmissions. Describe how FDM works. Describe the characteristics of the digital signal. Identify the advantages of digital technology.

18 xvi Describe how digital technology works with analog technology. Describe how pulse code modulation (PCM) works. Describe standards of digital voice transmissions. Describe time-division multiplexing (TDM). Describe optical signaling and its application. Describe digital loop carriers (DLCs).Define dimensioning. Describe the problems of engineering the voice network. Define LATA. Differentiate between an area code and a LATA. Define interlata. Describe how a phone number directs the path of a call. Differentiate between typical CO networks. Describe how a cellular network is organized. Describe how a cellular network handles a call Define Internet. Define Internet telephony. Identify the benefits of Internet telephony. Differentiate between the PSTN and the Internet as a voice carrier. Identify critical issues with Internet telephony. Identify the common steps in an Internet call. Define gateway. Define intranet. Discuss the use of VoIP for telephony by cable TV providers. Discuss how carrier systems are used in the PSTN. List the four media used to transport information. Define 2-wire full-duplex analog loop.

19 xvii Define carrier system. Distinguish between D4 and ESF framing in T carrier. Describe twisted-pair distribution in the wire center. Distinguish between bit rate and baud rate. Describe the SONET optical fiber standard. Describe subscriber signaling. Define interswitch signaling. Define in-band signaling. Define out-of-band signaling Define supervisory signaling. Describe how incoming calls are signaled. Describe call progress tones. Describe start dial signals. Describe interswitch supervisory signaling. Explain how the dialing process works. Describe pulse signaling. Describe DTMF signaling. Describe the North American Dialing Plan's address system. Define CCS. Identify the two main purposes of CCS. Describe a CCS network. Identify the functions of CCS in a voice network. Define signal transfer points (STPs). Define SS7. Describe the purpose for a signaling point (SP). Identify the typical SS7 network tasks during the placement of a call.

20 xviii Define switching. Explain the evolution of analog switches. Describe digital switches. Differentiate between analog and digital switches. Define time-division multiplexing (TDM). Identify the structure of TDM. Define time division switching (TDS). Describe how time-division switches work. Define space-division switching (SDS). Differentiate between TDS and SDS. Explain how time- and space-division stages work in the same switch. Describe the status of optical switching. Describe important criteria in determining applications to be deployed. Describe the process used to discover application needs. Determine the traffic model used to determine circuit quantities. Classroom Setup Student computers are not required for this seminar course. If the instructor wants to deliver supplemental activities or quizzes electronically, computers that meet the instructor's needs will be required for each student. Otherwise, all supplemental material can be distributed as hard-copy documents and completed by students using a pen and paper.

21 OBJECTIVES 1Lesson 1: Overview By the end of this lesson, you will be able to: Define telecommunications. Identify the different types of network providers and their functions. Describe today's telecommunications environment. Describe how today's environment was shaped by the history of legal and business practices. Identify two key objectives of telecommunications systems. Describe how today's environment was shaped by technological evolution. Describe the status of international telecommunications connectivity.

22 1-2 Basic Telecommunications Pre-Assessment Questions 1. The two parts of the telecommunications network which together provide communications capability are CPE and: a. The public switched telephone network. b. A competitive local exchange carrier. c. Switching. d. The Internet. 2. A key public policy goal of telecommunications is: a. Maintaining a competitive environment. b. Universal service. c. Federal and state regulation. d. Separation of local and long-distance companies. 3. A key development which greatly decreased the cost of telephony was: a. T Carrier. b. Satellite communications. c. The Internet. d. The transistor.

23 Overview 1-3 The Telecommunications Industry Telecommunications today is the product of the evolution of technology, business practice, and the law, dating back over 125 years in the United States. The forces that shaped the industry in the late 19 th century are still at work today. We are at another pivotal point in both technology and public policy that will shape telecommunications for decades. This lesson examines the current state of the telecommunications environment, introduces concepts and terminology which will be used throughout this course, and provides an understanding of the forces at work. Later lessons will provide details about the demand for telecommunications systems and services, and the technologies and businesses that meet the demand. The telecommunications industry is one of the largest industries in the world. It has existed for thousands of years; scholars have uncovered records dating from 3000 B.C. of signal fires used for long-distance communication. Telecommunications is communication at a distance (Greek telo), and this course will consider the industry as it evolved from sound (Greek phone) at a distance via the telephone. " telecommunications Communications at a distance. Many different pieces of equipment make up the hardware upon which the industry is built. Many of them are in plain view in homes and offices, and some are hidden behind the phone jack in the wall. Not all the items in the following figure actually plug into the phone jack in the wall. Newer technologies which allow for voice, fax or computer communication include the cable modem, the cell phone and the IP phone. Much of the course's content focuses on the telephone, but other ways of communicating will also be discussed. Figure 1-1: IP phones, cable modem, and cell phones support voice, fax, and data

24 1-4 Basic Telecommunications Growth in the United States The media have widely reported that little growth is occurring in voice telephony, and that most of the opportunity is in data communications. More accurately, though, growth is occurring in voice telephony over wireline networks. A wireline network is the traditional telephone network, which connects to the telephone using a pair of wires. The growth in cellular telephony has been substantial, however, considering the sheer numbers of subscribers, and that the third generation of cellular systems will soon be introduced. Figure 1-2: Growth in telephony since 1980 The data in Table 1-1 is from the United States market alone; it shows the magnitude of voice communications growth, and the split between cellular technologies and landline connections. The cellular number reflects the number of subscribers. The landline number reflects the number of lines in service; some subscribers have multiple lines. Figure 1-2 was created from the data in the table. Table 1-1: Telephony growth since 1980 Year End Landlines Cell Subscribers < Total (Millions) Rates are similar in Europe, where almost half of the traffic that travels across telephony lines is data, rather than voice. Although this data clearly illustrates growth in the cellular industry, the growth in landline telephony is less obvious. The growth in landline telecommunications has been created by the movement from a regulated monopoly environment to a deregulated, competitive environment.

25 Overview 1-5 Before the U.S. Telecommunications Reform Act of 1996, there were a large number of local exchange carriers (LEC), long-distance carriers, and cellular carriers. The long-distance carriers and cellular carriers were competitive, but the LECs each had a monopoly on local landline telecommunications in their territories, with only a few exceptions. The exceptions were companies called competitive access providers (CAPS). " local exchange carrier (LEC) A telco that provides telecommunications services within a limited geographical area (normally a metropolitan area as described by the census bureau). The 1996 Act opened local telecommunications to competition, and many new companies were formed to enter that market. In 1995, the LEC competitors were only 2.2 percent of total providers; by 2000 they made up 17.2 percent. Today, incumbent local exchange carriers (ILECs), competitive local exchange carriers (CLECs), and interexchange carriers (IXCs) all compete in telecommunications markets. " incumbent local exchange carrier (ILEC) A local exchange carrier which enjoyed monopoly status before 1996 in its service area, and thus has dominant market share. " competitive local exchange carrier (CLEC) A local exchange carrier formed to compete with the ILEC in a particular area; had minimal market share in " interexchange carrier (IXC) A telco which carries long-distance calls between LECs in separate LATAs. Figure 1-3: LECs share telecommunication markets with competitors The growth of the competitive LEC industry created many opportunities for employment, for investment, and for the equipment manufacturers to sell equipment to build local networks. It also gave customers, particularly small businesses, telecommunications alternatives that were not available before.

26 1-6 Basic Telecommunications An examination of the magnitude of the revenues involved also shows why so many entrepreneurs want to be involved in telecommunications, and why the incumbents are interested in protecting their market share. Figure 1-4: Telecommunications revenue distribution over time Figure 1-4 shows revenues gained and lost in terms of percentages. The toll revenue number shows revenues which were earned by IXCs, and "local toll," which is largely in-state long-distance revenue earned by the ILECs. The CLEC numbers from 1995 include those competitive access providers which provided direct connections between business customers and IXCs, in competition with the ILEC. From 1995 to 2000, the CLEC revenues went from U.S. $0.6B (0.3 % of the total) to $10.9B (3.8% of the total). At the same time, cellular providers went from $17.2B to $59.8B. Note that the holding companies that own many of the largest cellular companies also own the largest ILECs and IXCs. The total revenue earned by ILECs, CLECs, wireless, and toll providers in 2000 was $288.1B. Terms and Technology Since the early 1980s, in a business sense, telephony dealt with two different networks. One was made up of the equipment in the home or office building and was known as customer premise equipment (CPE). " customer premise equipment (CPE) All equipment on the customer side of the network. The subscriber rents or owns the CPE. Common CPE includes telephones, fax machines, PBX switches (i.e., exchanges), and so on.

27 Overview 1-7 Figure 1-5: Demarc is connection point between CPE and PSTN The other network was known as the public switched telephone network (PSTN). The place where the two networks met was called the point of demarcation, or the demarc. " point " public of demarcation (demarc) The piece of equipment on the customer's premises that marks the legal dividing line between the CPE and the PSTN. switched telephone network (PSTN) The portion of the dial-up switched telephone network that is not on a customer's premises, and is composed of the equipment owned by LECs, CLECs, and IXCs. Customer Premise Equipment On the customer's premises, the point of demarc is near where the telephone cables enter the building. On the premise side of the demarc, there is ordinarily an organized wiring plan that connects modular jacks to the demarc. In medium to larger business locations, the demarc is in an equipment room, which typically houses the PBX and other common equipment such as DSUs. Figure 1-6: Demarc is often housed in equipment room

28 1-8 Basic Telecommunications Most premises have a structured wiring plan, as shown in simplified form in Figure 1-6. Cables come out of the equipment room into wire closets. From the wire closets, cables are run to workstations. Most often, there are two modular jacks per workstation, one for voice, and one for data. They use 8-wire modular jacks and Cat 5 Cable. Premise cabling has been standardized. The standardization includes not only the wire, but the connectors and patch panels used to interconnect the cables. The two most common wiring standards are Category 3, which is suitable for voice and 10-Mbps Ethernet connections, and Category 5, which is suitable for voice and 100-Mbps Ethernet. Level 1 was used for voice, Level 2 for 4-Mbps token-ring LANs, and Level 4 for 16-Mbps token-ring LANs. Many locations are wired with one Cat 3 drop and one Cat 5 drop per workstation. More recently, the trend has been toward 100% Cat 5. In addition, many larger companies interconnect the wire closets with fiber optic cable, to more easily support gigabit Ethernet backbone data networks. The Public Switched Telephone Network On the other side of the demarc is the PSTN. The PSTN is one global, interconnected set of networks provided by public and private enterprises. The PSTN is made up of an access network, switches (i.e., exchanges), and transmission networks to interconnect all the switches. Access is the equipment that connects the CPE to the first switch in the network. For cellular providers, access is over radio. For wireline providers, access is provided over either copper cable or fiber-optic cable. Economics dictates that fiber-optic cable is used largely to connect to medium to large business locations, and residential and small business users are served by copper cable. The purpose of deploying switches is so that every subscriber need not have a direct connection to every other subscriber. Subscribers are connected to switches over the lines that form the access network, while switches are connected together with trunks. " line A connection between a telephone set and a switch which can handle one conversation. " trunk A direct communication line between two switching systems, which can handle one conversation. A central office trunk is the line connecting a PBX and the central office. A tie trunk is the line connecting one PBX to another PBX. Switches also provide concentration; a switch has more inputs(subscriber lines) than outputs (trunks). This arrangement is possible because only about onesixth of the phones are actually in use at any given time.

29 Overview 1-9 CLECs have one to a few switches in a city, whereas ILECs have many (30 to 50 in larger metropolitan areas). In the ILEC network, the switches are located in wire centers, so called because the switch is located in the center of the wire access network. Wire centers tend to be about 8 miles in diameter smaller in downtown areas, larger in suburban and rural areas. A medium-sized city might have 30 wire centers, and the larger wire centers may have several switches. The building housing the switch is called the central office, or CO. " wire center A central geographical area where all the access lines (wires) come together. " central office (CO) Telephone company building where subscriber lines (local loop) are connected to switching equipment for local and long-distance telephone transmissions and other services. Figure 1-7 illustrates three wire centers: Neighborhood A, Neighborhood B, and Neighborhood C. Each wire center has a switch in the CO that connects to the other switches. Figure 1-7: Wire center houses switch that is connected to all other switches A tandem is a switch that has trunks and not lines, and can handle only connection between switches. In Remote City is a fourth switch, called an access tandem, which serves to allow an IXC's toll switch a single point to connect to the ILEC network. All the local switches can be reached through the access tandem switch. " tandem A switch that only has trunks and can handle only connections between other switches. " access tandem A particular application of a tandem switch. Each metro area contains at least one access tandem, which allows a single point of access for IXCs. The trunks are carried over different transmission facilities. Types of

30 1-10 Basic Telecommunications transmission facilities include T carrier over copper cable, SONET carrier over fiber-optic cables, and digital radio. The switches, the trunks, the transmission facilities and the access tandem have one thing in common: They are shared by all the users on the network. One of the challenges in providing wire line telephone service is the cost of the access portion of the network. Access is the only part of the network that, for the majority of subscribers, is not shared. Although many CLECs have built fiber-optic networks to connect to businesses in cities, only the ILEC owns the copper cable that runs by most small businesses and residences, due to the cost. The cost of running new copper cable to a residence or small business is a large barrier to entry for those who want to provide service to that market. This barrier, or cost, is known as the last mile problem. The term "last mile" refers to the fact that the average length of that copper loop is about a mile. " last mile That part of the network that provides access to residences and small businesses, and is relatively costly to provide compared with the revenues derived from the service on that line. Figure 1-8: Access connects CPE to network In summary, only the ILEC has the capability to provide direct access to every premise. CLECs provide access only to larger businesses, cellular providers only to cell phones, and satellite or fixed radio carriers only to larger sites under special circumstances. This situation is not likely to change soon, due to the magnitude of the last mile problem. Considerable capital is required to provide access, as is right of way. As the CLECs built their access networks, they began to encounter resistance from building owners, who were questioning how many holes were going to be drilled into their foundations to allow fiber-optic cables to come in, and municipal governments, who were questioning the wisdom of having streets excavated repeatedly to bury new fiber cables.

31 Overview 1-11 Regulation and Public Policy An industry as large as telecommunications has many stakeholders. Some want prices to be lower, and some want them to be higher. Most are concerned with their own constituencies, and presume that the other stakeholders will advocate their own positions. Within the United States, two bodies are responsible for regulating some of the participants in the industry. At the federal level, the Federal Communications Commission (FCC) regulates the interstate aspects of telecommunications. Intrastate matters are left to the states, which have organizations often called public utility commissions (PUC). Figure 1-9: The FCC regulates interstate communications Historically, a certain amount of tension has always existed between the federal and state regulators. Other stakeholders include members of the industry, consumer and business groups, and customers. Politics enters in, particularly at the state level where local phone rates are set. Due to the international nature of telecommunications, international treaties and commissions are also involved in setting the environment in which the industry operates. In the United States, two key goals of public policy have influenced industry development from the beginning. The means to achieve these goals are still debated among stakeholders. Interconnectivity any phone should be able to dial any other phone. That is, all the networks are interconnected. Universal service anyone who wants a phone should be able to get (and afford) a phone. Standards The setting and enforcement of standards is a key to achieving interconnectivity. Many different groups are involved in setting standards. Following is a partial list.

32 1-12 Basic Telecommunications Standards Organizations! ANSI! IEEE! ITU! ETSI! ISO! IETF! Forums! Consortia! Telcordia Figure 1-10: Standards organizations The American National Standards Institute publishes many of the American standards through its T1 committee, and is the U.S. representative on many international standards organizations. The Institute of Electrical and Electronics Engineers has been fundamental to developing LAN standards. The International Telecommunications Union is an arm of the United Nations, and is the primary international body negotiating telecommunications standards. The European Telecommunications Standards Institute (ETSI) is the European Union's counterpart to ANSI. The International Organization for Standardization is the group that published the seven-layer OSI model for communications, and is instrumental in publishing quality methodologies. The Internet Engineering Task Force moderates Internet standard setting. Many forums are industry groups that have formed to promote a particular technology. They often produce "implementation agreements," which function much like standards but without the legal implications of a formal standard. Examples are the Frame Relay Forum, the ATM forum and the VoIP Forum. Various industry consortia are industry groups that form to work out industry issues. The Telecommunications Industry Association (TIA) is an example. Last on the list is Telcordia, which is a private company descended from the part of Bell Laboratories which wrote many of the voice network standards, including the Network Equipment Building System (NEBS), which is designed to create a safe working environment for equipment and people. Telcordia standards cover such issues as dial tone, how call waiting should work, voltage limits on E&M leads on trunks, and heat and humidity levels for central office buildings.