i

Design and Implementation of Voice Networks

Contents

Preface .................................................................................1

Prerequisites .......................................................................................1Who Should Study This Course? .......................................................2Key Topics ..........................................................................................2Course Objectives ...............................................................................3How Do I Use This Course? ...............................................................4

Real-World Scenarios ..................................................................4Pedagogy .....................................................................................4Key Terms ....................................................................................4

Resources Available in Instructor-Led Settings ..................................4Why Choose WestNet? ......................................................................5

Introduction .........................................................................7

Course Overview ................................................................................8

Module 1Telecommunications Concepts and Components .................................................9

Lesson 1Local Exchange Components ...............................................16

The Telephone System Hierarchy ....................................................17Class 5 Central Office: The Local Exchange .............................18Class 4 Central Office ................................................................20Tandem Central Offices ............................................................22Class 1 Office .............................................................................23

Class 5 Central Office Components ................................................24Switching and Routing ..............................................................25Semipermanent Circuit Connections .......................................25IXC POP ....................................................................................26Billing ........................................................................................27Customer Premises ....................................................................27

Local Exchange Calling Options ......................................................27LEC Does It All ..........................................................................27CLEC Serves as Reseller .............................................................28

Design and Implementation of Voice Networks

ii

CLECs Switch and ILECs Wire ..................................................28CLEC Does It All ........................................................................29

Activities ...........................................................................................30

Lesson 2Central Office Switching ......................................................32

The Talking Path ..............................................................................32Evolution of Telephone Switching ..................................................34

Manual Switching .....................................................................35Step-by-Step Switching and Rotary-Dial Telephones ...............37Crossbar Switching ....................................................................39Later Electro-mechanical Switching .........................................40Digital Switches .........................................................................41Touch-Tone Signaling ...............................................................41

How a Call is Made ..........................................................................43Dial Tone ...................................................................................43Entering a Telephone Number ..................................................43Call Routing ..............................................................................43Ringing ......................................................................................46Ending the Call .........................................................................46

Long Distance Voice Routing ...........................................................46Signaling ...........................................................................................47

In-Band vs.Out-of-Band Signaling ............................................................................47

SS7 .............................................................................................48Telephone Numbering System .........................................................48

The Dwindling Supply of Numbers ..........................................49LNP ............................................................................................50

Assigning Telephone Numbers ........................................................51Special Area Codes ...........................................................................51Special NXX Codes ...........................................................................51

Special Information: 555 ...........................................................51Hearing-Impaired Services: 800-855 .........................................52

Service Codes, or N11 Numbers .......................................................52Toll-Free: 800, 888, 877 .............................................................52Premium: 900 ............................................................................53International: 700 .....................................................................53Follow-You: 500 ........................................................................53

Activities ...........................................................................................54

Lesson 3Trunks, Lines, and Loops ......................................................56

Telecommunications Terms .............................................................57Loops ................................................................................................58Lines .................................................................................................58Trunks ...............................................................................................59Trunk Direction ................................................................................59Trunk Capacity .................................................................................59

Contents

iii

Analog Transmission ........................................................................60Channels and Bandwidth .........................................................61

Digital Transmission ........................................................................62PCM ...........................................................................................64Multiplexing ..............................................................................64Digital Bandwidth .....................................................................66

Special Access Trunks .......................................................................66Tie Lines ....................................................................................66Private Lines ..............................................................................67FX ..............................................................................................67Ring Down ................................................................................68Trunk Pricing .............................................................................68

Activities ...........................................................................................69

Lesson 4Central Office Exchange ......................................................71

Centrex .............................................................................................71Centrex Benefits ...............................................................................72Technical Requirements for Centrex ...............................................73

Distance From CO Switch .........................................................73Allocation of Call Paths ............................................................74CPE ............................................................................................74

Centrex Features ...............................................................................74Centrex vs. PBX ................................................................................75Activities ...........................................................................................76

Lesson 5Key Systems .........................................................................78

Key System Components .................................................................78Cordless Key Systems .......................................................................80Limitations of Key Systems ..............................................................81Hybrid Systems .................................................................................81Activities ...........................................................................................83

Lesson 6Buying a Telephone System .................................................84

Planning: First steps .........................................................................85Analyze Current Traffic Flow ....................................................85Identify Needs and Desires ........................................................85

Choosing a Switching System ..........................................................85Digital vs. Analog ......................................................................86Sizing a Telephone System ........................................................86System Features .........................................................................87

Selecting the Telephones .................................................................87Multiline vs. Single-Line ...........................................................87

Trunk Requirements .........................................................................88Cost ...........................................................................................88Features ......................................................................................89Physical Issues ...........................................................................89

Design and Implementation of Voice Networks

iv

Switch Capacity .........................................................................89Number Portability ...................................................................90

Determining Required Applications ................................................90ACD Systems .............................................................................91Messaging Systems ....................................................................91Wireless Systems .......................................................................92CTI .............................................................................................92IP Telephony .............................................................................92

Finding the Right Vendor ................................................................93Qualifying the Vendors .............................................................93Submitting an RFP .....................................................................93

Selecting the Vendor ........................................................................94Pricing .......................................................................................94Vendor Experience ....................................................................95

Shopping for Service and Support ...................................................95System Setup .............................................................................95Warranty ...................................................................................96Service Level Commitment .......................................................96Technical Support .....................................................................96System Security .........................................................................97Preventive Maintenance ...........................................................97

Activity .............................................................................................98Summary .............................................................................99Quiz ..................................................................................101

Module 2PBX and ACD Systems .....................................................109

Lesson 1PBX Fundamentals .............................................................126

PBX Components ...........................................................................126Trunks ......................................................................................127Extension Lines .......................................................................128Equipment Cabinet .................................................................128Telephones and Attendant Console .......................................129Administrative Terminal .........................................................129

Making a Call on a PBX .................................................................129Call Routing ...................................................................................130Supplementary PBX Features .........................................................131

DID ..........................................................................................131DISA .........................................................................................132

Station Set Features ........................................................................133Attendant Console Services ...........................................................134Administration and Management Reports ....................................135

Call Detail Reports ..................................................................135Test Reports .............................................................................135Busy-Hour Studies ...................................................................135

Contents

v

PBX Enhancements ........................................................................136Voice Response ........................................................................136Voice Recognition ...................................................................136Call Following .........................................................................137ACD .........................................................................................137Other Auxiliary Equipment ....................................................137

PBX Costs and Requirements .........................................................138Activities .........................................................................................139

Lesson 2PBX Features and Functions ...............................................142

Call Accounting .............................................................................142Authorization Codes ...............................................................143Account Codes ........................................................................143

Voice Mail Systems .........................................................................144FRL ...........................................................................................145Design Factors .........................................................................145Unified Messaging ...................................................................146Broadcasting ............................................................................147Voice Mail Security .................................................................147Automated Attendants ............................................................148CoR ..........................................................................................148Call Pickup ..............................................................................149Call Park ..................................................................................149Call Forwarding .......................................................................149Call Announcement ................................................................149Call Waiting ............................................................................149DAU .........................................................................................149Facility Test Call ......................................................................150

Activities .........................................................................................151

Lesson 3PBX Configurations ............................................................153

Overall Connectivity ......................................................................154Avaya DEFINITY Server with ACM System Components ..............155Digital Networking .........................................................................156

PN ............................................................................................156PPN ..........................................................................................156EPN ..........................................................................................156CSS ...........................................................................................156SN ............................................................................................157ATM SN ...................................................................................158

Main System Configurations .........................................................158PN Components .............................................................................159

TDM Bus ..................................................................................160Packet Bus ................................................................................160Port Circuits ............................................................................160Interface Circuits .....................................................................160

SPE ..................................................................................................163

Design and Implementation of Voice Networks

vi

ACM Software Architecture ............................................................164DEFINITY DCS Private Networks ...................................................164

LAN Gateway ...........................................................................164IP Trunking .............................................................................165

DCS Private Networks ....................................................................165DCS ..........................................................................................166Switch Components for DCS Networking ..............................168

IP-Enabling DEFINITY Servers ........................................................169IP Media Processor ..................................................................170CLAN .......................................................................................170

Upgrading DEFINITY Servers to S8700 Multi-Connect .................170Stage 1: Processor Replacement ..............................................171Stage 2: IP Enable the PNs .......................................................171Stage 3: Server Consolidation .................................................172

Upgrade the Data Network ............................................................172Activities .........................................................................................173

Lesson 4DEFINITY Server Hardware .................................................176

System Cabinets .............................................................................176Carriers ....................................................................................177CMC1 Media Gateway ............................................................177SCCI Media Gateway ...............................................................178MCC1 Media Gateway ............................................................179Floor Area and Load ................................................................179

Floor Area .........................................................................179Floor Load ........................................................................180

Floorplan Guidelines ......................................................................181CMC1 Configuration Guidelines ............................................181SCC1 Configuration Guidelines .............................................182MCC1 Configuration Guidelines ............................................183MDF .........................................................................................184

Environmental Conditions ............................................................184Temperature ............................................................................185Altitude and Air Pressure .........................................................185Humidity .................................................................................186Air Purity .................................................................................186Lighting ...................................................................................187Radio Frequency Noise ............................................................187

Cabinet Power Requirements .........................................................187AC Power .................................................................................187DC Power .................................................................................188Power Conditioning ................................................................188

Cabinet Power Components ..........................................................189DC Power Relay .......................................................................189Ring Generator ........................................................................189Fuses ........................................................................................189

Contents

vii

Power Backup ..........................................................................189UPS ...................................................................................190

Activities .........................................................................................191

Lesson 5IP Telephony .....................................................................192

Avaya Communication Manager ...................................................193Media Servers .................................................................................195

S8700 Media Server .................................................................195Availability/Reliability ......................................................196Multi-Connect vs. IP-Connect .........................................197Interoperability ................................................................198

S8500 .......................................................................................198S8300 Media Server with G700 Gateway ................................198

Survivability .....................................................................199S8100 .......................................................................................199

Media Gateways .............................................................................200G350 ........................................................................................200G600 ........................................................................................200G650 ........................................................................................201

IP Office ..........................................................................................201Supported Telephones ....................................................................202

Analog .....................................................................................202Digital ......................................................................................202IP ..............................................................................................203Wireless ...................................................................................203

Activities .........................................................................................205Extended Activities .........................................................................206

Lesson 6PBX Networking ................................................................208

Private Communications Networks ...............................................209Cost Savings ............................................................................211Improved Efficiency ................................................................212Enhanced User Satisfaction .....................................................212

Tandem Trunks and Tandem Switching ........................................213Network Configurations ................................................................213

Series ........................................................................................213Star ...........................................................................................215Three-System Star ....................................................................216

PBX Security ...................................................................................217IP PBX Security ........................................................................217

Activities .........................................................................................219

Design and Implementation of Voice Networks

viii

Lesson 7Basics of Automatic Call Distributor ...................................222

Agents and Splits ............................................................................222What an ACD Does ........................................................................223

Automatic-In Processing .........................................................224DID Processing ........................................................................224

Split Queue Processing ...................................................................224Announcements ......................................................................224Answer Supervision .................................................................225Abandoned Call Search ...........................................................225Intraflow and Interflow ...........................................................226Call Distribution Methods ......................................................226

Vectors ............................................................................................227Vector Flow .............................................................................227Vector Management ................................................................228

Call Flow Problems ...........................................................228Activities .........................................................................................230

Summary ...........................................................................232Quiz ..................................................................................234

Module 3Point-to-Point Telecommunications Protocols .......................................243

Lesson 1Physical and Logical Circuits ..............................................247

Circuits and Virtual Circuits ..........................................................247PVCs and SVCs ........................................................................250

SVC Information Transfer ..............................................................251Connecting to WAN Circuits .........................................................252DCE and DTE .................................................................................252

DTE-to-DCE Protocols .............................................................253Layer Upon Layer ....................................................................253

Activities .........................................................................................256

Lesson 2Summary of Data Rates .....................................................258

Point-to-Point Links .......................................................................258Analog Lines ............................................................................259DDS ..........................................................................................259SW56 .......................................................................................259High-Speed Services .................................................................259

Various Data Rates and Associated Applications ...........................260Bandwidth ......................................................................................261Activities .........................................................................................263

Contents

ix

Lesson 3Dial-Up and Leased Lines ...................................................265

Dial-up Connections ......................................................................265Leased Lines ...................................................................................266DDS .................................................................................................267Activities .........................................................................................269

Lesson 4T-Carriers ...........................................................................271

Digitizing Voice ..............................................................................271T-Carriers ........................................................................................272DS0 or Fractional T1 .......................................................................274T1 ....................................................................................................275T3 and North American Digital Signal Hierarchy .........................279Circuit Costs ...................................................................................279Activities .........................................................................................280

Lesson 5Asymmetric Digital Subscriber Line ....................................281

Digital Subscriber Lines and Internet Access .................................281Options for Local High-Speed Internet Access ..............................282DSL .................................................................................................283

Physical Requirements ............................................................285ADSL ...............................................................................................286Activity ...........................................................................................290

Lesson 6Cable Modems ..................................................................292

Cable Modem Technology .............................................................292ADSL or Cable Modem? The Subscriber’s Perspective ...................294Activities .........................................................................................296

Lesson 7Synchronous Optical Network ...........................................297

The SONET Standard ......................................................................297SONET Advantages .........................................................................298SONET Protocol Architecture .........................................................299

Path Layer ................................................................................299Line Layer ................................................................................300Section Layer ...........................................................................301Photonic Layer ........................................................................301

SONET Multiplexing ......................................................................302SONET Frame Format .....................................................................304

Virtual Tributaries ...................................................................306Clock Synchronization ............................................................307

SONET Network Elements ..............................................................307Add/Drop MUX/Demultiplexer ..............................................307Broadband Digital Cross-Connect ..........................................308Wideband Digital Cross-Connect ...........................................309

Design and Implementation of Voice Networks

x

Terminating MUX ...................................................................309Regenerator .............................................................................310

Activities .........................................................................................311Summary ...........................................................................312Quiz ..................................................................................314

Module 4Switched Telecommunications Protocols ........................317

Lesson 1Circuit- and Packet-Switched Networks .............................323

Data Link Layer Protocols ..............................................................323Reliable WAN Networks .................................................................324

Packet-Switched Networks ......................................................325Circuit-Switched Networks .....................................................325

Activities .........................................................................................327

Lesson 2Serial Line Internet Protocol and Point-to-Point Protocol ......................................................328

SLIP .................................................................................................328SLIP Frame Delimiters .............................................................329Drawbacks to SLIP ...................................................................330

Compressed SLIP ............................................................................330PPP ..................................................................................................331

Information Frames ................................................................331Link Control Frames ...............................................................332Network Control Frames .........................................................332Zero Bit Insertion ....................................................................333

Activities .........................................................................................334

Lesson 3Integrated Services Digital Network ...................................335

Integrated Digital Networks ...........................................................335ISDN Services ..................................................................................336Call-by-Call Service ........................................................................339Channel Bonding and NFAS ..........................................................340ISDN Signaling ...............................................................................341

DSS1 .........................................................................................342PSS1 .........................................................................................343Q.SIG and ISDN Supplementary Services ...............................344

Activities .........................................................................................346

Lesson 4Asynchronous Transfer Mode ............................................347

The Need for ATM ..........................................................................348Transfer Modes ........................................................................348STM ..........................................................................................348

Contents

xi

PTM .........................................................................................349ATM .........................................................................................350

Connection-Oriented Mode ...........................................................351Fixed-Length Data Cells .................................................................353Header Details ................................................................................354B-ISDN and ATM ............................................................................355

AAL ..........................................................................................356Convergence Sublayer (CS) ..............................................357Segmentation and Reassembly (SAR) Sublayer ................358

ATM Layer ...............................................................................359Physical Layer ..........................................................................360

TC Sublayer ......................................................................360TC Cell Rate Decoupling ..................................................361Physical Medium-Dependent Sublayer ............................361

Activities .........................................................................................362

Lesson 5Frame Relay .......................................................................363

What is Frame Relay? .....................................................................364Frame Relay Terms .........................................................................366Permanent and Virtual Circuits .....................................................367Frame Relay Operation ...................................................................368Frame Relay Frame .........................................................................368

Information Field ....................................................................369Frame Relay Header Field ........................................................369

Flow Control ..................................................................................370Congestion ..............................................................................370Management Frames ...............................................................371

Frame Relay Addressing .................................................................371Interconnecting LANs Using Frame Relay .....................................374Frame Relay Implementation Options ..........................................374

Private Frame Relay .................................................................375Public Frame Relay ..................................................................376Hybrid Frame Relay .................................................................376

End-User Access to Frame Relay Networks ....................................377The “Extra Hop” Problem ..............................................................379Frame Relay vs. Private Line Networking ......................................380Frame Relay Services ......................................................................382Public Frame Relay Services ...........................................................382Bandwidth on Demand ..................................................................383Conditional Bursting .....................................................................384

VoIP over Public Frame Relay Services ....................................384Cost Considerations .......................................................................385Carrier Choice Considerations .......................................................385

CIR ...........................................................................................385Congestion Control ................................................................386Reports and Statistics ..............................................................386

Frame Relay Network Requirements ..............................................386Activities .........................................................................................387

Design and Implementation of Voice Networks

xii

Lesson 6Switched Multimegabit Data Service .................................393

SMDS Operation .............................................................................393Switched ..................................................................................393Multimegabit ...........................................................................394

SNI ..................................................................................................394SMDS Protocols ..............................................................................395

SMDS Interface Protocol .........................................................396SIP-1 ..................................................................................396SIP-2 ..................................................................................396SIP-3 ..................................................................................396

DXI .................................................................................................397Router Functions .....................................................................398DSU Functions ........................................................................398

Advantages and Disadvantages ......................................................399Activity ...........................................................................................401

Lesson 7X.25 ..................................................................................403

X.25 Services ..................................................................................403Addressing ...............................................................................404

X.25 Protocols ................................................................................404Layer 3: PLP .............................................................................405Layer 2: LAPB ..........................................................................405Layer 1: X.21 and X.21bis .......................................................405PAD ..........................................................................................405

PLP ..................................................................................................407Overhead and Performance Limitations ........................................409Activity ...........................................................................................411

Summary ...........................................................................412Quiz ..................................................................................414

Module 5Traffic Engineering ..........................................................419

Lesson 1 Traffic Engineering Concepts ............................................423

Carried Load ...................................................................................423Conversation Time ..................................................................424Operating Time .......................................................................425Holding Time ..........................................................................425Constant Distribution .............................................................426Exponential Distribution ........................................................426

Probability ......................................................................................426GOS ................................................................................................427Trunk Usage ...................................................................................428

CCS ..........................................................................................428Erlang ......................................................................................428

Contents

xiii

The Erlang B Traffic Formula .........................................................429Erlang C and Poisson Tables ..........................................................431

Poisson: Immediate Redial ......................................................431Erlang C: Infinite Queue .........................................................431

No Formula is Perfect .....................................................................431Estimating Total System Capacity .................................................432

Outbound Trunk Capacity ......................................................432Tie Trunks ................................................................................432Voice Mail Capacity ................................................................434Ports .........................................................................................434Storage Time ............................................................................435PBX Processing Capacity .........................................................436

Adjusting to Changes .....................................................................437Activities .........................................................................................438

Lesson 2Traffic Data Sources ...........................................................441

Data Sources ...................................................................................441Gathering Data ...............................................................................442Experiments ...................................................................................443

Experimental Conditions ........................................................443Number of Experiments ..........................................................444

Sampling ........................................................................................444Bias ..........................................................................................445Sample Size ..............................................................................445Sample Spread .........................................................................446

Planning a Study ............................................................................447Activities .........................................................................................448

Lesson 3Busy-Hour Engineering ......................................................450

The Busy Hour ................................................................................450Constant Busy Hour ................................................................451Bouncing Busy Hour ...............................................................451

Grade of Service vs. Cost ................................................................451Potential PBX Bottlenecks ..............................................................452

Tone Detectors ........................................................................453Processor Occupancy ...............................................................453Time Slots ................................................................................453Modules ...................................................................................453

Consider All Traffic, All Paths ........................................................453Activities .........................................................................................454

Summary ...........................................................................457Quiz ..................................................................................459

Course Quiz ......................................................................461

Glossary ............................................................................471

Design and Implementation of Voice Networks

xiv

Index ................................................................................489

Overall Course Evaluation Survey.....................................503