Cisco Press Cisco Voice over IP CVOICE 3rd Edition Jul 2008

Cisco Press

800 East 96th Street

Indianapolis, IN 46240

Authorized Self-Study Guide

Cisco Voice over IP (CVOICE),

Third Edition

Kevin Wallace, CCIE No. 7945

Authorized Self-Study Guide

Cisco Voice over IP (CVOICE),

Third Edition

Kevin Wallace

Copyright© 2009 Cisco Systems, Inc.

Published by:

Cisco Press

800 East 96th Street

Indianapolis, IN 46240 USA

All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means,

electronic or mechanical, including photocopying, recording, or by any information storage and retrieval

system, without written permission from the publisher, except for the inclusion of brief quotations in a

review.

Printed in the United States of America

First Printing July 2008

Library of Congress Cataloging-in-Publication Data:

Wallace, Kevin, CCNP.

Authorized self-study guide : Cisco Voice over IP (CVoice) / Kevin Wallace. — 3rd ed.

p. cm.

ISBN 978-1-58705-554-6 (hbk. : CD-ROM) 1. Internet telephony—Examinations—Study guides. 2.

Electronic data processing personnel—Certification—Study guides. I. Title. II. Title: Cisco Voice over IP

(CVoice).

TK5105.8865.W3345 2008

004.69’5—dc22

2008022672

ISBN-13: 978-1-58705-554-6

ISBN-10: 1-58705-554-6

Warning and Disclaimer

This book is designed to provide information about the Cisco Voice over IP (CVOICE) certification

topics. Every effort has been made to make this book as complete and as accurate as possible, but no

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accompany it.

The opinions expressed in this book belong to the author and are not necessarily those of Cisco

Systems, Inc.

ii Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)

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iii

Publisher: Paul Boger

Associate Publisher: Dave Dusthimer

Cisco Press Program Manager: Jeff Brady

Executive Editor: Brett Bartow

Managing Editor: Patrick Kanouse

Development Editor: Andrew Cupp

Senior Project Editor: San Dee Phillips

Copy Editor: Barbara Hacha

Technical Editors: Michelle Plumb

Anthony Sequeira

Editorial Assistant: Vanessa Evans

Book and Cover Designer: Louisa Adair

Composition: Bronkella Publishing, LLC

Indexer: Tim Wright

Proofreader: Jovana San Nicholas-Shirley

About the Author

Kevin Wallace, CCIE No. 7945, is a certified Cisco instructor, and he teaches courses in

the Cisco CCSP, CCVP, and CCNP tracks. With 19 years of Cisco networking experience,

Kevin has been a network design specialist for the Walt Disney World Resort and a net￾work manager for Eastern Kentucky University. Kevin holds a bachelor of science degree

in electrical engineering from the University of Kentucky. Kevin also is a CCVP, CCSP,

CCNP, and CCDP with multiple Cisco security and IP communications specializations.

iv Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)

About the Technical Reviewers

Michelle Plumb is a full-time certified Cisco instructor for SkillSoft, focusing on the

Cisco IP Telephony track. Michelle has more than 18 years in the field as an IT and tele￾phony specialist and maintains a high level of Cisco and Microsoft certifications, including

CCVP, CCSI, and MCSE NT 4.0/2000. Michelle has been a technical reviewer for numer￾ous books related to the Cisco CCNP and Cisco IP Telephony course material track.

Anthony Sequeira, CCIE No. 15626, completed the CCIE in Routing and Switching in

January 2006. He is currently pursuing the CCIE in Security. For the past 15 years, he has

written and lectured to massive audiences about the latest in networking technologies.

Anthony is currently a senior technical instructor and certified Cisco instructor for

SkillSoft. Anthony lives with his wife and daughter in Florida. When he is not reading

about the latest Cisco innovations, he is exploring the Florida skies in a Cessna.

v

Dedication

I dedicate this book to my two daughters, Stacie and Sabrina. You are growing up far

too fast.

Acknowledgments

My thanks go out to my fellow instructors at SkillSoft and our manager, Tom Warrick. It is

an honor to work side by side with you all. Also, thanks to Brett Bartow at Cisco Press for

his faith in me and allowing me to simultaneously author two books.

On a personal note, I acknowledge and thank God for His blessings in my life. Also, my

wife, Vivian, and my daughters, Stacie and Sabrina, have patiently awaited the completion

of this book and the CCNA Security Official Exam Certification Guide. Thank you for your

patience during these past few months.

vi Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)

vii

Contents at a Glance

Foreword xviii

Introduction xix

Chapter 1 Introducing Voice over IP Networks 3

Chapter 2 Considering VoIP Design Elements 55

Chapter 3 Routing Calls over Analog Voice Ports 125

Chapter 4 Performing Call Signaling over Digital Voice Ports 185

Chapter 5 Examining VoIP Gateways and Gateway Control Protocols 247

Chapter 6 Identifying Dial Plan Characteristics 321

Chapter 7 Configuring Advanced Dial Plans 367

Chapter 8 Configuring H.323 Gatekeepers 441

Chapter 9 Establishing a Connection with an Internet Telephony Service

Provider 521

Appendix Answers to Chapter Review Questions 553

Index 558

viii Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)

Contents

Foreword xviii

Introduction xix

Chapter 1 Introducing Voice over IP Networks 3

VoIP Fundamentals 3

Cisco Unified Communications Architecture 3

VoIP Overview 4

Components of a VoIP Network 6

VoIP Functions 7

VoIP Signaling Protocols 9

The H.323 Umbrella 9

MGCP 11

Session Initiation Protocol 12

Skinny Client Control Protocol 12

Comparing VoIP Signaling Protocols 12

VoIP Service Considerations 15

Media Transmission Protocols 16

Real-Time Transport Protocol 16

RTP Control Protocol 17

Compressed RTP 18

Secure RTP 20

Introducing VoIP Gateways 21

Understanding Gateways 21

Modern Gateway Hardware Platforms 24

Well-Known and Widely Used Enterprise Models 27

Standalone Voice Gateways 30

Summary of Voice Gateways 34

IP Telephony Deployment Models 36

Summary 50

Chapter Review Questions 51

ix

Chapter 2 Considering VoIP Design Elements 55

VoIP Fundamentals 55

IP Networking and Audio Clarity 55

Audio Quality Measurement 61

VoIP and QoS 63

Transporting Modulated Data over IP Networks 66

Understanding Fax/Modem Pass-Through, Relay, and Store and

Forward 67

Modem Relay 71

Gateway Signaling Protocols and Fax Pass-Through and Relay 74

DTMF Support 82

Processing Voice Packets with Codecs and DSPs 84

Codecs 85

Impact of Voice Samples and Packet Size on Bandwidth 87

Data Link Overhead 88

Security and Tunneling Overhead 88

Calculating the Total Bandwidth for a VoIP Call 88

Effects of Voice Activity Detection on Bandwidth 90

DSP 91

Codec Complexity 95

DSP Requirements for Media Resources 98

Configuring Conferencing and Transcoding on Voice Gateways 107

Cisco IOS Configuration Commands for Enhanced Media

Resources 114

Verifying Media Resources 119

Summary 120

Chapter Review Questions 121

Chapter 3 Routing Calls over Analog Voice Ports 125

Introducing Analog Voice Applications on Cisco IOS Routers 125

Local Calls 125

On-Net Calls 126

Off-Net Calls 127

PLAR Calls 127

PBX-to-PBX Calls 128

Intercluster Trunk Calls 129

x Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)

On-Net to Off-Net Calls 130

Summarizing Examples of Voice Port Applications 131

Introducing Analog Voice Ports on Cisco IOS Routers 132

Voice Ports 132

Analog Voice Ports 133

Configuring Analog Voice Ports 144

Trunks 150

Centralized Automated Message Accounting 154

Direct Inward Dial 157

Timers and Timing 159

Verifying Voice Ports 160

Introducing Dial Peers 164

Understanding Call Legs 164

Understanding Dial Peers 165

Configuring POTS Dial Peers 167

Configuring VoIP Dial Peers 169

Configuring Destination Pattern Options 172

Matching Inbound Dial Peers 175

Characteristics of the Default Dial Peer 177

Matching Outbound Dial Peers 179

Summary 180

Chapter Review Questions 181

Chapter 4 Performing Call Signaling over Digital Voice Ports 185

Introducing Digital Voice Ports 185

Digital Trunks 186

T1 CAS 188

E1 R2 CAS 189

ISDN 191

ISDN Signaling 195

Configuring a T1 CAS Trunk 208

Configuring an E1 R2 Trunk 218

Configuring an ISDN Trunk 220

Verifying Digital Voice Ports 225

xi

Using QSIG for Digital Signaling 232

QSIG Overview 232

Configuring QSIG Support 236

Verifying QSIG Trunks 239

Summary 242

Chapter Review Questions 243

Chapter 5 Examining VoIP Gateways and Gateway Control Protocols 247

Configuring H.323 247

H.323 Gateway Overview 247

Why H.323 250

H.323 Network Components 253

H.323 Call Establishment and Maintenance 258

H.323 Call Flows 259

H.323 Multipoint Conferences 261

Configuring H.323 Gateways 263

Verifying an H.323 Gateway 274

Implementing MGCP Gateways 275

MGCP Overview 275

Why MGCP 276

MGCP Architecture 277

Basic MGCP Concepts 280

MGCP Call Flows 283

Configuring MGCP Gateways 285

Verifying MGCP 290

Implementing SIP Gateways 293

SIP Overview 294

Why SIP 296

SIP Architecture 297

SIP Call Flow 299

SIP Addressing 302

SIP DTMF Considerations 304

Configuring SIP 305

Verifying SIP Gateways 309

Summary 315

Chapter Review Questions 316

Chapter 6 Identifying Dial Plan Characteristics 321

Introducing Dial Plans 321

Dial Plan Overview 321

Endpoint Addressing 324

Call Routing and Path Selection 325

Digit Manipulation 325

Calling Privileges 326

Call Coverage 326

Scalable Dial Plans 326

PSTN Dial Plan Requirements 328

ISDN Dial Plan Requirements 330

Configuring PSTN Dial Plans 331

Verifying PSTN Dial Plans 341

Numbering Plan Fundamentals 348

Numbering Plan Overview 348

Numbering Plan Categories 349

Scalable Numbering Plans 351

Overlapping Numbering Plans 352

Private and Public Numbering Plan Integration 353

Enhancing and Extending an Existing Plan to Accommodate VoIP 355

911 Services 357

Implementing a Numbering Plan Example 359

Summary 361

Chapter Review Questions 362

Chapter 7 Configuring Advanced Dial Plans 367

Configuring Digit Manipulation 367

Digit Manipulation 367

Digit Collection and Consumption 370

Digit Stripping 371

Digit Forwarding 372

Digit Prefixing 373

Number Expansion 374

Caller ID Number Manipulation 377

Voice Translation Rules and Profiles 380

xiii

Voice Translation Profiles Versus the dialplan-pattern Command 390

Configuring Digit Manipulation 393

Configuring Path Selection 397

Call Routing and Path Selection 397

Dial Peer Matching 398

Matching Dial Peers in a Hunt Group 404

H.323 Dial-Peer Configuration Best Practices 405

Path Selection Strategies 406

Site-Code Dialing and Toll-Bypass 407

Tail-End Hop–Off (TEHO) 409

Configuring Site-Code Dialing and Toll-Bypass 410

Outbound Site-Code Dialing Example 415

Inbound Site-Code Dialing Example 416

Configuring TEHO 417

Implementing Calling Privileges on Cisco IOS Gateways 420

Calling Privileges 420

Understanding COR on Cisco IOS Gateways 421

Understanding COR for SRST and CME 426

Configuring COR for Cisco Unified Communications Manager

Express 427

Configuring COR for SRST 433

Verifying COR 434

Summary 434

Chapter Review Questions 436

Chapter 8 Configuring H.323 Gatekeepers 441

H.323 Gatekeeper Fundamentals 441

Gatekeeper Overview 441

Gatekeeper Hardware and Software Requirements 445

Gatekeeper Signaling 445

Call Flows with a Gatekeeper 464

Zone Prefixes 468

Technology Prefixes 469

Gatekeeper Call Routing 471

Directory Gatekeepers 479

xiv Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)