Implementing Voice Over IP

Implementing Voice Over IP

IMPLEMENTING VOICE OVER IP Copyright 6 2003 by John Wiley & Sons, Inc. All rights reserved.Published by John Wiley & Sons, Inc., Hoboken, New Jersey.Published simultaneously in Canada.No part of this publication may be reproduced, stored in a retrieval system, or transmitted in anyform or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise,except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, withouteither the prior written permission of the Publisher, or authorization through payment of theappropriate per-copy fee to the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers,MA 01923, 978-750-8400, fax 978-750-4470, or on the web at www.copyright.com. Requests tothe Publisher for permission should be addressed to the Permissions Department, John Wiley &Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, e-mail:permreq@wiley.com.Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their beste¤orts in preparing this book, they make no representations or warranties with respect to theaccuracy or completeness of the contents of this book and specifically disclaim any impliedwarranties of merchantability or fitness for a particular purpose. No warranty may be created orextended by sales representatives or written sales materials. The advice and strategies containedherein may not be suitable for your situation. You should consult with a professional whereappropriate. Neither the publisher nor author shall be liable for any loss of profit or any othercommercial damages, including but not limited to special, incidental, consequential, or otherdamages.For general information on our other products and services please contact our Customer CareDepartment within the U.S. at 877-762-2974, outside the U.S. at 317-572-3993 or fax 317-572-4002.Wiley also publishes its books in a variety of electronic formats. Some content that appears inprint, however, may not be available in electronic format.Library of Congress Cataloging-in-Publication Data is available.ISBN 0-471-21666-6Printed in the United States of America10987654321 IMPLEMENTING VOICEOVER IPBHUMIP KHASNABISHLexington, Massachusetts, USAA JOHN WILEY & SONS, INC. PUBLICATION This book is dedicated to:Srijesa, Inrava, and Ashmita;My parents, sisters, and brothers;My teachers, present and pastColleagues, and friends; andAll of those who consciously andhonestly contributed tomaking me what I am today. CONTENTSPreface xiAcknowledgments xv1 Background and Introduction 1The Paradigms, 2VoIP for Residential Customers, 2VoIP for Enterprise Customers, 3Functionally Layered Architectures, 6Organization of the Book, 12Epilogue, 14References, 142 Technologies Supporting VoIP 15Voice Signal Processing, 15Low-Bit-Rate Voice Signal Encoding, 16Voice Signal Framing and Packetization, 16Packet Voice Transmission, 18Mechanisms and Protocols, 18Packet Voice Bu¤ering for Delay Jitter Compensation, 25QoS Enforcement and Impairment Mitigation Techniques, 26Preventive Mechanisms, 27Reactive Mechanisms, 27Future Directions, 29Epilogue, 30References, 30vii 3 Evolution of VoIP Signaling Protocols 32Switch-Based versus Server-Based VoIP, 34H.225 and H.245 Protocols, 34Session Initiation Protocol (SIP), 35MGCP and H.248/Megaco, 39Stream Control Transmission Protocol (SCTP), 41Bearer Independent Call Control (BICC), 42Future Directions, 43The Promising Protocols, 43Interworking of PSTN and IP Domain Services, 45Hybrid Signaling Model, 45References, 474 Criteria for Evaluating VoIP Service 49Service Requirements Before Call Setup Attempts, 50Service Requirements During Call Setup Attempts, 50Service Requirements During a VoIP Session, 51Voice Coding and Processing Delay, 52Voice Envelop Delay, 53Voice Packet Loss, 55Voice Frame Unpacking and Packet Delay Jitter Bu¤er, 55Management of Voice Quality During a VoIP Session, 56Service Requirements After a VoIP Session Is Complete, 57References, 585 A Testbed for Evaluating VoIP Service 59Description of the Testbed/Network Configuration, 60PSTN Emulation, 63IP Network and Emulation of Network Impairments, 64SS7 Network Emulation and Connectivity, 65Network Time Server, 65Telephone Call Emulation Suites, 65Epilogue, 67References, 676 VoIP Deployment in Enterprises 68IP-Based Endpoints: Desktop and Conference Phones, 69IP-PBX, IP Centrex, and IP-Based PBX Tie Lines, 71IP-VPN and VoIP for Tele-Workers, 77Web-Based Call and Contact Centers, 79Next-Generation Enterprise Networks, 81Customers’ Expectations, 81Process Reengineering and Consolidation, 83viiiCONTENTS Proactive Maintenance, 83Support for QoS, 84Support for Multimedia, 84Improving Wired Access, 85Wireless Access, 86Enterprise Network Management, 88Epilogue, 88References, 917 VoIP in the Public Networks 93IP-Based Tandem or CLASS-4 or Long-Distance Services, 93Elements Required to O¤er VoIP-Based LD Service, 95A Simple Call Flow, 96Network Evolution Issues, 98VoIP in the Access or Local Loop, 99PSTN Networks, 102An Architectural Option, 104An Alternative Architectural Option, 105CATV Networks, 107Broadband Wireless Access (Local Loop) Networks, 110IP-Based Centrex and PBX Services, 111Epilogue, 113References, 1168 VoIP for Global Communications 117VoIP in Multinational Corporate Networks, 117VoIP for Consumers’ International Telephone Calls, 122Epilogue, 125References, 1259 Conclusions and Challenges 127Guidelines for Implementing VoIP, 129VoIP Implementation Challenges, 132Simplicity and Ease of Use, 133Nonstop Service, 133High-Quality Service, 133Scalable Solutions, 133Interoperability, 134Authentication and Security, 134Legal and Public Safety–Related Services, 134Cost-E¤ective Implementation, 135Epilogue, 135References, 136CONTENTSix [...]... of Call Setup in IP Telephony for Tests and Measurements 152 Appendix C Evaluation of VoIP Services 169 Glossary of Acronyms and Terms 178 Index 205 x CONTENTS PREFACE In general, voice transmission over the Internet protocol (IP) , or VoIP, means transmission of real-time voice signals and associated call control information over an IP- based (public or private) network. The term IP telephony is com- monly... specifications in G.764 and G.765 standards [5,6] for carrying packetized voice over ISDN-compatible networks. For voice transmission over the Internet, the IETF recommends encapsulation of voice frames using the RTP (RFC 1889) for UDP (RFC 768)-based transfer of information over an IP network. We discuss these in later sections. VOICE SIGNAL PROCESSING 17 This book is dedicated to: Srijesa, Inrava,... belong solely to Bhumip Khasnabish, Massachusetts, USA. 2 300 to 3400 Hz (or 3.4 KHz) of analog speech signal. or the integrated access device (IAD), it is possible to use either voice over ATM or VoIP over ATM to support the VoDSL service. If VoIP is used for VoDSL, then it is highly likely that the IAD has to support SIP or MGCP (migrating to H.248/Megaco)-based clients as voice terminals. Finally,... using IP phones and IP- based access, transport, and control networks. These networks can be either logically over- layed on the public Internet or connected to the Internet via one or more gate- ways or edge routers with appropriate service protection functions embedded in them. In this book, I use VoIP and IP telephony synonymously, most of the times. This book grew out of my participation in many VoIP-related... of the voice signal, which commonly results in degrada- tion of voice quality. Additional hardware-based echo-canceller and higher- speed transmission mechanisms are generally required to improve voice quality in such scenarios. As shown in Figure 2-2, IP- based transmission of a digitized voice signal for (real-time) telephony service requires the addition of multiple levels of encapsulation overheads.... 10 MIPS, while G.723.1 requires 16 MIPS of processing capacity. The voice quality delivered by these CODECs is considered acceptable in a variety of network impairment scenarios. Therefore, most VoIP product manufacturers support G.723, G.729, and G.711 voice coding options in their products. Voice Signal Framing and Packetization PSTN uses the traditional circuit switching method to transmit the voice encoder’s... Geneva, 1996. 4. D. Minoli and E. Minoli, Delivering Voice over Frame Relay and ATM, John Wiley & Sons, New York, 1998. 5. G.764 Recommendation, Voice Packetization—Packetized Voice Protocols, ITU-T, Geneva, 1990. 30 TECHNOLOGIES SUPPORTING VoIP phone. The circuit switching method is very reliable, but it is neither flexible nor e‰cient for voice signal transmission, where almost 60% of the time... require- ment for a voice session (or call) unless a header compression mechanism is utilized. In addition, when both real-time voice and non-real-time data tra‰c are transported over the same IP network, proactive tra‰c management tech- niques need to be incorporated in the routers and switches in order to maintain timely—evenly spaced and with low loss—transmission of voice tra‰c. Other- wise, the voice quality... the deployment of VoIP ser- vices in their networks. xi the VoIP GWs or IP- PSTN MGWs. Appendix C presents experimental evalu- ation of the quality of transmission of voice signal and DTMF digits under both impairment-free (i.e., typical PSTN) and impaired—that is, with added IP- level packet delay, delay jitter, and packet loss—networking conditions. EPILOGUE Implementation of VoIP has reached a level... underflow and over ow—should PACKET VOICE TRANSMISSION 25 three of which are G.711, G.723, and G.729. G.711 uses pulse code modulation (PCM) technique and generates a 64 Kbps voice stream. G.723 uses (CELP) technique to produce a 5.3 Kbps voice stream, and G.723.1 uses (MP-MLQ) technique to produce a 6.4 Kbps voice stream. Both G.729 and G.729A use (CS-ACELP) technique to produce an 8 Kbps voice stream. Usually . VoIP Deployment in Enterprises 6 8IP- Based Endpoints: Desktop and Conference Phones, 6 9IP- PBX, IP Centrex, and IP- Based PBX Tie Lines, 7 1IP- VPN and VoIP. general, voice transmission over the Internet protocol (IP) , or VoIP, meanstransmission of real-time voice signals and associated call control informationover