Voice and Video Conferencing Fundamentals (Networking Technology Series) » (New Edition)

About the Authors

Scott Firestone holds a master’s degree in computer science from MIT and has designed

video conferencing and voice products since 1992, resulting in five patents. During his

10 years as a technical leader at Cisco, Scott developed architectures and solutions related to

video conferencing, voice and video streaming, and voice-over-IP security.

Thiya Ramalingam is an engineering manager for the Unified Communications organization at

Cisco. Thiya holds a master’s degree in computer engineering and an MBA from San Jose State

University. He holds several patents issued and pending, related to voice and video over IP. Thiya

is currently leading the development of multimedia conferencing products at Cisco.

Steve Fry is a technical leader in the Unified Communications organization at Cisco. For the past

several years, Steve has been involved in the design and development of telephony and

conferencing products. Prior to his conferencing projects, he was a principal engineer on the

CallManager MGCP gateway products. He is currently leading product development in video

conferencing.

Voice and Video Conferencing Fundamentals

Design, develop, select, deploy, and support advanced IP-based audio and video conferencing systems

Scott Firestone, Thiya Ramalingam, Steve Fry

As audio and video conferencing move rapidly into the mainstream, customers and end users are demanding unprecedented performance, reliability, scalability, and security. In Voice and Video Conferencing Fundamentals, three leading experts systematically introduce the principles, technologies, and protocols underlying today’s state-of-the-art conferencing systems. Discover how to use these concepts and techniques to deliver unified, presence-enabled services that integrate voice, video, telephony, networks, and the Internet—and enable breakthrough business collaboration.

The authors begin with a clear, concise overview of current voice and video conferencing, including system components, operational modes, endpoints, features, and user interactivity. Next, they illuminate conferencing architectures, offering practical insights for designing today’s complex IP-based conferencing and collaboration systems.

Topics covered in this book include video codecs, media control, SIP and H.323 protocols and applications, lip synchronization in video conferencing, security, and much more. Throughout the book, the authors draw on their extensive experience as Cisco® technical leaders, showing how to avoid the most common pitfalls that arise in planning, deployment, and administration.

Voice and Video Conferencing Fundamentals is for every professional involved with audio or video conferencing: network and system administrators, engineers, technology managers, and Cisco solution partners alike. Whether you’re involved with design, development, selection, implementation, management, or support, you’ll find the in-depth knowledge you need to succeed.

Scott Firestone holds a master’s degree in computer science from MIT and has designed video conferencing and voice products since 1992, resulting in five patents. Thiya Ramalingam is an engineering manager for the Cisco Unified Communications organization. Thiya holds a master’s degree in computer engineering and an MBA degree from San Jose State University. Steve Fry, a technical leader in the Cisco Unified Communication organization, has spent the last several years designing and developing telephony and conferencing products.

• Thoroughly understand the fundamentals of audio and video conferencing over IP networks
• Architect networks for optimal performance and reliability in conferencing applications
• Leverage new advances in video architecture, from emerging codecs to distributed implementations
• Understand how SIP and H.323 compare, and when to use each
• Optimize synchronization between audio and video
• Secure conferencing traffic without compromising performance or connectivity
• Learn how to evaluate vendors and make better buying decisions

Foreword

Introduction

Chapter 1 Overview of Conferencing Services

Chapter 2 Conferencing System Design and Architecture

Chapter 3 Fundamentals of Video Compression

Chapter 4 Media Control and Transport

Chapter 5 Signaling Protocols: Conferencing Using SIP

Chapter 6 Signaling Protocols: Conferencing Using H.

Chapter 7 Lip Synchronization in Video Conferencing

Chapter 8 Security Design in Conferencing

Appendix A Video Codec Standards

This book is part of the Cisco Press® Fundamentals Series. Books in this series introduce networking professionals to new networking technologies, covering network topologies, sample deployment concepts, protocols, and management techniques.

Category: Cisco Press/Networking

Covers: Voice and video conferencing

1587052687

Foreword xviii

Introduction xix

Chapter 1 Overview of Conferencing Services 3

Conference Types 3

Ad Hoc Conferences 4

Reservationless Conferences 5

Scheduled Conferences 6

Voice and Video Conferencing Components 9

Video Conferencing Modes 11

Voice-Activated Conferences 11

Continuous Presence Conferences 13

Lecture Mode and Round-Robin Conferences 15

Types of Endpoints 16

Desktop Conferencing Systems 16

Room Conferencing Systems 16

Telepresence Systems 16

Video Controls: Far-End Camera Control 17

Text Overlay 18

Summary 18

Chapter 2 Conferencing System Design and Architecture 21

Components of a Conferencing System 21

User Interface 23

Conference Control 25

Control Plane 26

Media Plane 27

Conferencing Architectures 37

Centralized Architecture 37

Distributed Architecture 38

Full-Mesh Networks 40

Advanced Conferencing Scenarios 41

Escalation of Point-to-Point-to-Multipoint Call 41

Lecture Mode Conferences 41

Panel Mode Conference 42

Floor Control 42

Video Mixing and Switching Scenarios 42

Summary 43

References 43

Chapter 3 Fundamentals of Video Compression 45

Evaluating Video Quality, Bit Rate, and Signal-to-Noise Ratio 45

Video Source Formats 47

Profiles and Levels 47

Frame Rates, Form Factors, and Layouts 47

Standard and High Definitions 48

Color Formats 49

Basics of Video Coding 52

Preprocessing 52

Post-Processing 54

Encoder Overview 55

Hybrid Coding 72

Hybrid Decoder 72

P-Frames 74

Hybrid Encoder 74

Predictor Loop 76

Motion Estimation 77

B-Frames 82

Predictor Loops for Parameters 86

Error Resiliency 88

Scalable Layered Codecs 91

SNR and Spatial Scalability 93

Temporal Scalability 95

Switching Frames 99

Video Codecs 100

Video Stream Hierarchy 100

Macroblocks 101

HD-Capable Codecs 102

Summary 102

References 103

Chapter 4 Media Control and Transport 105

Overview of RTP 105

RTP Header 107

RTP Port Numbers 111

SSRC Collisions 111

RTP Header Extensions 112

Overview of RTCP 113

RTCP Packet Headers 113

RTCP Sender Report 114

RTCP Receiver Report 116

RTCP Source Description (SDES) 117

RTCP BYE 119

RTCP APP 120

RTP Devices in Conference Systems 120

RTP Translator 120

RTP Mixer 123

Audio Mixer 123

Video MCU 124

Video Switcher 124

Video Stream RTP Formats 126

H.263 126

H.264 133

Detecting Stream Loss 141

Summary 142

References 143

Chapter 5 Signaling Protocols: Conferencing Using SIP 145

SIP Overview 145

User Agent 146

Proxy Server 146

Redirect Server 147

Registrar 147

SIP Transactions and Dialogs 148

SIP Messages 149

SIP Requests 149

SIP Responses 152

SIP Record Routing 153

Event Subscription and Notification 154

Session Description Protocol 155

SIP Conferencing Models 157

Conference URI 157

Early and Delayed Offer 158

DTMF Support 159

Ad Hoc Audio Conferencing 160

Ad Hoc Video Conferencing 162

Video SDP Extensions 163

Bandwidth Information in the SDP 167

Multiple Stream Support and Grouping of Media Lines 168

Escalation and De-escalation 169

Media Control Support 172

Scheduled Conferences 173

Entry IVR 174

In-Conference Features 177

Roll Call 177

Hold and Resume 178

Mute and Unmute 179

Outdial 179

RSVP/QoS Support in Conferencing Flows 180

Summary 182

References 183

Chapter 6 Signaling Protocols: Conferencing Using H.323 185

H.323 Overview 185

H.323 Endpoint Aliasing 187

H.225 Call Signaling 188

H.225 Message Format 188

Common H.225 Message Types Used in H.323 Signaling 189

H.245 Control Protocol 191

H.245 Messages 192

Video-Specific H.245 Messages 202

H.323 Fast Connect Mode 204

Using the Empty Capability Set 207

Call Hold Signaling with the Empty Capability Set 207

Call Transfer with the Empty Capability Set 207

H.323 Device Types 208

H.323 Gatekeeper Services 209

Required H.323 Gatekeeper Features 209

Optional H.323 Gatekeeper Features 210

Gatekeeper Signaling Options 211

Gatekeeper RAS Signaling 212

Mid-Call Bandwidth Requests 214

Configuring a Gatekeeper in Cisco Unified CallManager 215

Configuring Gatekeeper Support in a Cisco IOS Router 217

H.225 Call Setup for Video Devices Using a Gatekeeper 217

Using Service Prefixes with MCUs 219

Summary 220

References 220

Chapter 7 Lip Synchronization in Video Conferencing 223

Understanding Lip Sync Skew 223

Human Perceptions 223

Measuring Skew 225

Delay Accumulation 226

Delays in the Network Path 228

Lip Sync Approaches 229

Poor Man’s Lip Sync 230

Common Reference Lip Sync 232

Understanding the Sender Side 232

Sender Audio Path 233

Video Source Format 235

Sender Video Path 238

Understanding the Receive Side 241

Audio Receiver Path 241

Receiver Video Path 243

Types of Playout Devices 244

RTP 244

Canonical RTP Model 244

RTP Time Stamps 246

Using RTP for Buffer-Level Management 247

Correlating Timebases Using RTCP 250

NTP 250

Forming RTCP Packets 251

Using RTCP for Media Synchronization 252

Lip Sync Policy 254

Summary 255

References 255

Chapter 8 Security Design in Conferencing 257

Security Fundamentals 257

Threats 258

Confidentiality Attacks 258

Denial-of-Service Attacks 259

Authentication and Identity Attacks 262

Network Infrastructure Attacks 263

Endpoint Infrastructure Attacks 266

Server Attacks 267

Configuring Basic Security 269

Port Usage 270

H.323 Port Usage 270

SIP Port Usage 275

SCCP Port Usage 275

Preset Port Numbers 276

NAT and PAT 276

NAT Classifications 277

NAT Complications for VoIP Protocols 284

NAT ALGs 285

NAT/FW Traversal Solutions 285

Encryption Basics 299

Symmetric Encryption 299

Secure Hashes 299

Asymmetric Encryption: Public Key Cryptography 300

Nonrepudiation 309

Key Distribution 309

IPsec and TLS for Secure Signaling 310

IPsec 311

TLS 311

Media Encryption 312

security-descriptions 312

MIKEY 313

H.323 Encryption: H.235 313

H.235.1 314

H.235.2 316

H.235.3 319

H.235.6 319

SIP Encryption 321

SIP-Digest 321

SCCP Encryption 324

Summary 324

References 325

Appendix A Video Codec Standards 327

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