ign and Implementation Considerations Chapter 8 Interworking 141 Chapter 9 Questions to Ask of a Service Provider Offering and an SBC Vendor Part III: Deploying SIP Trunks Chapter 10 Deployment Scenarios Chapter 11 Deployment Steps and Best Practices 243 Chapter 12 Case Studies Chapter 13 Future of Unified Communications 297 Index 311 viii SIP Trunking Contents Introduction xix Part I: From TDM Trunking to SIP Trunking Chapter 1 Overview of IP Telephony History of IP Telephony 1 Basic Components of IP Telephony Microphones and Speakers 2 Digital Signal Processors 3 Comparing VoIP Signaling Protocols 4 Call Control Elements of IP Telephony 5 Other Physical Components of IP Telephony IP Phones 6 IP-PBX 6 Ethernet Switches 6 Non-IP Phone IP Telephony Devices WAN Connectivity Device 6 Voice Gateways 7 Supplementary Services 9 Summary 10 Chapter 2 Trends in IP Telephony 11 Major Trends in IP Communications 12 Enterprise IP Communications Endpoints Desktop Handset Trends Enterprise Softphone IP Phone Trends Enterprise WiFi IP Phone Trends 17 Cellular Phone Trends Within Enterprises and Their Effects on SIP Trunking 18 Endpoint Trends in Enterprises and Their Effects on SIP Trunk Feature Trends in SIP Trunking Within the Enterprise 20 Feature Trends in SIP Trunking Between Enterprises 22 Feature Trends in SIP Trunk for PSTN Access Feature Trends in Advanced SIP Trunking Features from Service Providers 26 Feature Trends for Call Centers Services from SIP Trunk Providers Summary 30 Chapter 3 Transitioning to SIP Trunks Phase I: Assess the Current State of Trunking Phase II: Determining the Priority of the Project Phase III: Gather Information from the Local SPs Phase IV: Conducting a Pilot Implementation of SIP Trunks for PSTN Access Phase V: Transitioning a Live Department to SIP Trunks Phase VI: Transition to SIP Trunking for Call Center Locations Phase VII: Transition to SIP Trunking at Headquarters Locations Phase VIII: Transition to SIP Trunking of Branch Locations Phase IX: Transition Any Remaining Trunk to SIP Trun