ip telephony deploaying voip protocols and ims infrastructure

IP Telephony Deploying VoIP Protocols and IMS Infrastructure, Second Edition Olivier Hersent CEO of Actility A John Wiley and Sons, Ltd., Publication IP Telephony Deploying VoIP Protocols and IMS Infrastructure, Second Edition IP Telephony Deploying VoIP Protocols and IMS Infrastructure, Second Edition Olivier Hersent CEO of Actility A John Wiley and Sons, Ltd., Publication This edition first published 2011  2011 John Wiley & Sons Ltd. First edition published 2005 Registered office John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, United Kingdom For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com. The right of the author to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. 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If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloguing-in-Publication Data Hersent, Olivier. IP telephony : deploying VoIP protocols and IMS infrastructure / Olivier Hersent. — 2nd ed. p. cm. Includes index. ISBN 978-0-470-66584-8 (cloth) 1. Internet telephony. 2. Convergence (Telecommunication) I. Title. TK5105.8865.H47 20010 004.69  5–dc22 2010024553 A catalogue record for this book is available from the British Library. Print ISBN 9780470665848 (H/B) ePDF ISBN: 9780470973264 oBook ISBN: 9780470973080 Set in 10/12 Times-Roman by Laserwords Private Limited, Chennai, India Contents Abbreviations ix Glossary xxi Preface xxix 1 Multimedia Over Packet 1 1.1 Transporting voice, fax, and video over a packet network 1 1.1.1 A Darwinian view of voice transport 1 1.1.2 Voice and video over IP with RTP and RTCP 5 1.2 Encoding media streams 16 1.2.1 Codecs 16 1.2.2 DTMF 39 1.2.3 Fax 40 2 H.323: Packet-based Multimedia Communications Systems 49 2.1 Introduction 49 2.1.1 Understanding H.323 50 2.1.2 Development of the standard 52 2.1.3 Relation between H.323 and H.245 versions, H.323 annexes, and related specifications 55 2.1.4 Where to find the documentation 57 2.2 H.323 step by step 58 2.2.1 The ‘hello world case’: simple voice call from terminal A to terminal B 58 vi CONTENTS 2.2.2 A more complex case: calling a public phone from the Internet using a gatekeeper 72 2.2.3 The gatekeeper-routed model 79 2.2.4 H.323 calls across multiple zones or administrative domains 86 2.3 Optimizing and enhancing H.323 95 2.3.1 Issues in H.323v1 95 2.3.2 The ‘early H.245’ procedure 99 2.3.3 The ‘fast-connect’ procedure 99 2.3.4 H.245 tunneling 103 2.3.5 Reverting to normal operation 106 2.3.6 Using RAS properly and only when required 106 2.4 Conferencing with H.323 108 2.4.1 The MCU conference bridge, MC and MP subsystems 108 2.4.2 Creating or joining a conference 109 2.4.3 H.332 113 2.5 Directories and numbering 114 2.5.1 Introduction 114 2.5.2 Contacting an email alias with H.323 and the DNS 115 2.5.3 E164 numbers and IP telephony 116 2.6 H.323 security 124 2.6.1 Typical deployment cases 124 2.6.2 H.235 131 2.7 Supplementary services 148 2.7.1 Supplementary services using H.450 148 2.7.2 Proper use of H.450 supplementary services, future directions for implementation of supplementary services 154 2.8 Future work on H.323 155 3 The Session Initiation Protocol (SIP) 159 3.1 The origin and purpose of SIP 159 3.1.1 From RFC 2543 to RFC 3261 163 3.1.2 From RFC 3261 to 3GPP, 3GPP2 and TISPAN 166 3.2 Overview of a simple SIP call 167 3.2.1 Basic call scenario 167 3.2.2 Syntax of SIP messages 169 3.3 Call handling services with SIP 219 3.3.1 Location and registration 220 3.3.2 The proxy function, back to back user agents 230 3.3.3 Some common services 242 3.3.4 Multiparty conferencing 244 3.4 SIP security 250 3.4.1 Media security 250 3.4.2 Message exchange security 251 CONTENTS vii 3.5 Instant messaging (IM) and presence 254 3.5.1 Common profile for instant messaging (CPIM) 255 3.5.2 RFC 3265, Specific Event Notification 260 3.5.3 RFC 3428: SIP extensions for instant messaging 266 4 The 3GPP IP Multimedia Subsystem (IMS) Architecture 269 4.1 Introduction 269 4.1.1 Centralized value added services platforms on switched telephone networks: the ‘tromboning’ issue 269 4.1.2 The ‘Intelligent Network’ (IN) 270 4.1.3 How VoIP solves the ‘tromboning’ issue. The value added services architecture of 3GPP IMS 270 4.1.4 The IMS architecture is ideal for mobile networks but not only 273 4.2 Overview of the IMS architecture 274 4.2.1 Registration 274 4.2.2 SIP session establishment in an IMS environment 275 4.2.3 A few remarks on the IMS architecture 278 4.3 The IMS CSCFs 279 4.3.1 The Proxy-CSCF 279 4.3.2 The Serving-CSCF (S-CSCF) and Application Servers (AS) 282 4.3.3 The Media Resource Function (MRF) 286 4.4 The full picture: 3GPP release 8, TISPAN 288 4.4.1 The packet core domain: the evolved packet system 289 4.4.2 The IMS domain 299 4.4.3 Summary of SIP extensions required in an IMS network 311 5 The Media Gateway to Media Controller Protocol (MGCP) 313 5.1 Introduction: why MGCP? 313 5.1.1 Stimulus protocols 313 5.1.2 Decomposed gateways 315 5.1.3 Some history 317 5.2 MGCP 1.0 318 5.2.1 The MGCP connection model 321 5.2.2 The protocol 323 5.2.3 Handling of fax 350 5.2.4 Extensions for phone user interface control 354 5.3 Sample MGCP call flows 358 5.3.1 Call set-up 358 5.3.2 DTMF tones 364 5.3.3 Call release 364 5.4 The future of MGCP 365 viii CONTENTS 6 Advanced Topics: Call Redirection 367 6.1 Call redirection in VoIP networks 367 6.1.1 Call transfer, call forward, call deflection 367 6.1.2 Summary of major issues 368 6.1.3 Reference network configurations in the PSTN 371 6.1.4 Reference network configurations with VoIP 374 6.1.5 How to signal call transfer? 387 6.1.6 VoIP call redirection and call routing 388 6.1.7 Conclusion 390 7 Advanced Topics: NAT Traversal 393 7.1 Introduction to Network Address Translation 393 7.1.1 One-to-one NAT 393 7.1.2 NAPT 394 7.1.3 Issues with NAT and NAPT 396 7.2 Workarounds for VoIP when the network cannot be controlled 398 7.2.1 Ringing the proper phone 398 7.2.2 Using port forwarding to solve the wrong media address problem 399 7.2.3 STUN 399 7.2.4 Other proposals: COMEDIA and TURN 402 7.3 Recommended network design for service providers 404 7.3.1 Avoid NAT in the customer premises for VoIP 405 7.3.2 Media proxies 412 7.3.3 Security considerations 415 7.4 Conclusion 416 Annex 417 Index 427 [...]... voice path through the IP network Today more and more service providers and enterprises, as they have become confident in the VoIP technology and quality of service of IP networks, deploy VoIP applications in order to enjoy the location independence and greater flexibility of the technology With more successful deployments, VoIP is gaining in maturity, and the cost of VoIP gateways and IP phones is quickly... previous frame) Private phone switch with a VoIP wide area network interface Most IP- PBXs have an H.323 WAN interface See also IPBX Same as IP- PBX Some use the term IPBX for private phone switches which use only VoIP (i.e., the phones are also IP phones), whereas an IP- PBX can be a traditional PBX with analog phones and only uses a WAN VoIP interface See IP- PBX Statistical variance of packet interarrival... them and understand the main parameters required for the transmission of the resulting data The most popular VoIP standards are presented in Chapter 2 (H.323), Chapter 3 (SIP), and Chapter 5 (MGCP) In Chapter 4 we describe the IMS (IP multimedia subsystem), which has become the standard architecture for large scale residential VoIP networks (using the TISPAN profile, also described in Chapter 3) and. .. protocol level VoIP products, which were using totally proprietary protocols before the year 2000, began to interwork first using H.323 and then MGCP and SIP also Simultaneously, some operators began to deploy huge VoIP residential networks, reaching millions of users In 2005, most deployments used standard protocols; however, the architectural details of the VoIP networks were still proprietary and specific... detail, protocols such as H.323 or MGCP which are not used inside the IMS system, but as peer networks or at the edges of the IMS network These protocols are still used intensively in existing VoIP networks, and are still the best candidates in some situations, e.g., videoconferencing and ISDN PBX trunking for H.323, or business IP phone control for MGCP It is likely that future evolutions of SIP and IMS. .. progressively alleviate the need for other protocols in VoIP; however, most VoIP operators will still need to support multiple VoIP protocols in the next 5 to 10 years We hope that this book will help network engineers to deploy, maintain, or upgrade their VoIP networks, using each protocol where it fits best, and with full awareness of the potential pitfalls and difficulties ... quality of service for IP data flows, and guidelines to properly dimension an IP network for voice It also delves into the details of voice coding technology, and the influence of the selected voice coder and the transmission channel parameters on perceived voice quality In theory, it is sufficient to read the VoIP standards in order to become an efficient VoIP engineer Although reading the standards is always... the VoIP messages carried by these packets The second issue comes from the widespread confusion between private telephony techniques and public telephony techniques for call transfers In both cases the chapter presents techniques that were deployed successfully, and explains the pros and cons of each possible method PREFACE xxxiii CONCLUSION When the first edition of this book was published, VoIP standards... most of these teams felt confident that VoIP could be deployed on a wide scale in the future, and in the mean time tried to evaluate what could be the impact of VoIP, compared to previous technologies It took a relatively long time to understand the reasons that would lead a service provider to deploy VoIP instead of traditional switched voice networks Initially VoIP was presented as a technology that... An H.323 zone is the set of all H.323 end points, MCs, MCUs, and gateways managed by a single gatekeeper Preface VoIP 1998–2004, 6 YEARS FROM R&D LABS TO LARGE SCALE DEPLOYMENTS Since 1998 Voice over IP, in short VoIP, has been the favorite buzzword of the telecom industry In 1998, IP was not yet as established and dominant as it is today, and most telecom engineers still believed that only ATM technology . IP Telephony Deploying VoIP Protocols and IMS Infrastructure, Second Edition Olivier Hersent CEO of Actility A John Wiley and Sons, Ltd., Publication IP Telephony Deploying VoIP Protocols and. VoIP Protocols and IMS Infrastructure, Second Edition IP Telephony Deploying VoIP Protocols and IMS Infrastructure, Second Edition Olivier Hersent CEO of Actility A John Wiley and Sons, Ltd., Publication This. Data Hersent, Olivier. IP telephony : deploying VoIP protocols and IMS infrastructure / Olivier Hersent. — 2nd ed. p. cm. Includes index. ISBN 978-0-470-66584-8 (cloth) 1. Internet telephony. 2. Convergence