VoIP and Unified Communications: Internet Telephony and the Future Voice Network

CONTENTS

Preface

Acknowledgments

1 IP Technology Disrupts Voice Telephony

1.1 Introduction to the Public Switched Telephone Network

1.2 The Digital PSTN

1.3 The Packet Revolution in Telephony

1.3.1 Summary of Packet Switching

1.3.2 Link Capacity: TDM versus Packets

1.3.3 VoIP and “The Cloud”

IN SHORT: Reading Network Drawings

2 Traditional Telephones Still Set Expectations

2.1 Availability: How the Bell System Ensured Service

2.2 Call Completion

2.3 Sound Quality: Encoding for Recognizable Voices

2.4 Low Latency

2.5 Call Setup Delays

2.6 Impairments Controlled: Echo, Singing, Distortion, Noise

3 From Circuits to Packets

3.1 Data and Signaling Preceded Voice

3.1.1 X.25 Packet Data Service

3.1.2 SS7: PSTN Signaling on Packets

3.1.3 ISDN

3.2 Putting Voice into Packets

3.2.1 Voice Encoding

3.2.2 Dicing and Splicing Voice Streams

3.2.3 The Latency Budget

4 Packet Transmission and Switching

4.1 The Physical Layer: Transmission

IN SHORT: The Endian Wars

4.2 Data Link Protocols

4.3 IP, the Network Protocol

4.4 Layer 4 Transport Protocols

4.4.1 Transmission Control Protocol

4.4.2 User Datagram Protocol

4.4.3 Stream Control Transmission Protocol

4.5 Higher Layer Processes

4.5.1 RTP

4.5.2 RTCP

4.5.3 Multiplexing RTP and RTCP on One UDP Port

4.5.4 RTP Mixers and Translators

4.5.5 Layered Encoding

4.5.6 Profiles for Audio and Video Conferences

4.5.7 Security via Encryption

IN SHORT: Public Key Infrastructure (PKI)

4.6 Saving Bandwidth

4.6.1 Voice Compression

4.6.2 Header Compression

4.6.3 Silence ...