VoIP and Unified Communications (eBook)

WILLIAM A. FLANAGAN is President and founder of Flanagan Consulting. With three decades of telecommunications experience, Mr. Flanagan is an expert in voice and data technologies, products, markets, and customers. His network designs have solved problems for enterprises, government agencies, and carriers.

1. IP Technology Disrupts Voice Telephony 1

1.A Introduction to the Public Switched Telephone Network 1

1.B The Digital PSTN 2

1.C The Packet Revolution in Telephony 7

2. Traditional Telephones Still Set Expectations 16

2.A Availability: How the Bell System ensured service 16

2.B Call Completion 18

2.C Sound Quality: encoding for recognizable voices 18

2.D Low Latency 20

2.E Call Setup Delays 21

2.F Impairments controlled: echo, singing, distortion, noise 22

3. From Circuits to Packets 25

3.A Data and Signaling Preceded Voice 25

3.B Putting Voice into Packets 27

4. Packet Transmission and Switching 33

4.A The Physical Layer: Transmission 34

4.B Data Link Protocols 36

4.C IP, the Network Protocol 38

4.D Layer 4 Transport Protocols 40

4.E Higher Layer Processes 47

4.F Saving Bandwidth 55

4.G Differences: Circuit vs. Packet Switched 61

5. VoIP Signaling and Call Processing 67

5.A What packet voice and UC systems share 67

5.B Session Initiation Protocol (SIP) 69

5.C Session Description Protocol 91

5.D Media Gateway Control Protocol 95

5.E H. 323 108

5.F Directory services 120

6. VoIP and Unified Communications Define the Future 123

6.A Voice As Before, with Additions 123

6.B Legacy Services to Keep and Improve with VoIP 123

6.C Facsimile transmission 134

6.D Phone Features Added with VoIP/UC 143

7. How VoIP and UC Features to Consider 149

7.A Space, Power, and Cooling 150

7.B Priority for voice, Video, Fax Pakets 150

7.C Packets per Second 152

7.D Bandwidth 152

7.E Security Issues 153

7.F First Migration Steps While Keeping Legacy Equipment 159

8. Interconnections to Global Services 163

8.A Media Gateways 163

8.B SIP Trunking 166

8.C Operating VoIP Across Network Address Translation 170

8.D Session Border Controller 179

8.E Supporting multiple carrier connections 183

8.F Mobility and Wireless Access 184

9. Network Management for VoIP and UC 188

9.A Starting Right 189

9.B Continuous Monitoring and Management 191

9.C Troubleshooting and Repair 195

10. Cost Analysis and Payback Calculation 199

11. Examples of Hardware and Software203

11.A IP Phones 203

11.B Gateways 206

11.C Session Border Controllers 209

11.D Call Switching Servers 209

11.E Hosted VoIP/UC Service.

11.F Management Systems/Workstations 215

12. Appendices 217

12.A Acronyms and Definitions 217

12.B Reference Documents 226

12.C Message and Error Codes 233

13. Index 236