Switching to VoIP: A Solutions Manual for Network Professionals

by Theodore Wallingford

Overview

More and more businesses today have their receive phone service through Internet instead of local phone company lines. Many businesses are also using their internal local and wide-area network infrastructure to replace legacy enterprise telephone networks. This migration to a single network carrying voice and data is called convergence, and it's revolutionizing the world of telecommunications by slashing costs and empowering users. The technology of families driving this convergence is called VoIP, or Voice over IP.

VoIP has advanced Internet-based telephony to a viable solution, piquing the interest of companies small and large. The primary reason for migrating to VoIP is cost, as it equalizes the costs of long distance calls, local calls, and e-mails to fractions of a penny per use. But the real enterprise turn-on is how VoIP empowers businesses to mold and customize telecom and datacom solutions using a single, cohesive networking platform. These business drivers are so compelling that legacy telephony is going the way of the dinosaur, yielding to Voice over IP as the dominant enterprise communications paradigm.

Developed from real-world experience by a senior developer, O'Reilly's Switching to VoIP provides solutions for the most common VoIP migration challenges. So if you're a network professional who is migrating from a traditional telephony system to a modern, feature-rich network, this book is a must-have. You'll discover the strengths and weaknesses of circuit-switched and packet-switched networks, how VoIP systems impact network infrastructure, as well as solutions for common challenges involved with IP voice migrations. Among the challenges discussed and projects presented:

• building a softPBX
• configuring IP phones
• ensuring quality of service
• scalability
• standards-compliance
• topological considerations
• coordinating a complete system 'switchover'
• migrating applications like voicemail and directory services
• retro-interfacing to traditional telephony
• supporting mobile users
• security and survivability
• dealing with the challenges of NAT

To help you grasp the core principles at work, Switching to VoIP uses a combination of strategy and hands-on "how-to" that introduce VoIP routers and media gateways, various makes of IP telephone equipment, legacy analog phones, IPTables and Linux firewalls, and the Asterisk open source PBX software by Digium. You'll learn how to build an IP-based or legacy-compatible phone system and voicemail system complete with e-mail integration while becoming familiar with VoIP protocols and devices. Switching to VoIP remains vendor-neutral and advocates standards, not brands. Some of the standards explored include:

• SIP
• H.323, SCCP, and IAX
• Voice codecs
• 802.3af
• Type of Service, IP precedence, DiffServ, and RSVP
• 802.1a/b/g WLAN

If VoIP has your attention, like so many others, then Switching to VoIP will help you build your own system, install it, and begin making calls. It's the only thing left between you and a modern telecom network.

Product Details

ISBN-13:	9780596008680
Publisher:	O'Reilly Media, Incorporated
Publication date:	06/11/2005
Pages:	502
Product dimensions:	7.00(w) x 9.19(h) x 1.10(d)

About the Author

Born and raised in Detroit, MI, Ted Wallingford began working with information systems at the age of 7, when his father brought home a used Timex Sinclair 1000 computer and a notepad of hand-written BASIC programs from a garage sale. This little machine was the start of an eclectic career in the business of bits and bytes.

While working in the data center at ad agency J. Walter Thompson, Ted began to write articles for computer magazines. This led him into writing marketing materials for Gateway Computer and the former Amiga Inc., where he was also webmaster in 1999. As I.T. Director for a large, private construction firm, Ted transformed a single-operator midrange computer room into a mission-critical 24x7 data center hosting services for lines of business across the country. Ted has designed and implemented Voice over IP on networks large and small. He offers network design for VoIP systems and product management assistance for up'n'coming VoIP carriers through his macVoIP.com consulting practice. Ted believes that VoIP and the Internet are today's revolution in distance communication.

Aside from technology and writing, Ted has served as a member of the board of trustees for an international adoption agency in suburban Cleveland, where he lives with his wife and two children. Ted is currently working on Switching to VoIP for O'Reilly Media.

Table of Contents

Dedication; Foreword; Preface; Audience; Assumptions Made in This Book; Conventions; Where to Get More; Safari Enabled; How to Contact Us; Acknowledgments; Chapter 1: Voice and Data: Two Separate Worlds?; 1.1 The PSTN; 1.2 Key Systems and PBXs; 1.3 Limits of Traditional Telephony; 1.4 VoIP in the Home; 1.5 VoIP in Business; 1.6 VoIP's Changing Reputation; 1.7 Key Issues: Voice and Data: Two Separate Worlds; Chapter 2: Voice over Data: Many Conversations, One Network; 2.1 VoIP or IP Telephony; 2.2 Distributed Versus Mainframe; 2.3 Key Issues: Voice over Data: Many Conversations, One Network; Chapter 3: Linux as a PBX; 3.1 Free Telephony Software; 3.2 Installing Legacy Interface Cards; 3.3 Compiling and Installing Asterisk; 3.4 Monitoring Asterisk; 3.5 Key Issues: Linux as a PBX; Chapter 4: Circuit-Switched Telephony; 4.1 Regulation and Organization of the PSTN; 4.2 Components of the PSTN; 4.3 Customer Premises Equipment; 4.4 Time Division Multiplexing; 4.5 Point-to-Point Trunking; 4.6 Legacy Endpoints; 4.7 Dial-Plan and PBX Design; 4.8 Key Issues: Circuit-Switched Telephony; Chapter 5: Enterprise Telephony Applications; 5.1 Application Terminology; 5.2 Basic Call Handling; 5.3 Administrative Applications; 5.4 Messaging Applications; 5.6 Advanced Call-Handling Applications; 5.7 CTI Applications; 5.8 Key Issues: Telephony Applications; Chapter 6: Replacing the Voice Circuit with VoIP; 6.1 The "Dumb" Transport; 6.2 Voice Channels; 6.3 Project 6.1. Set Up Custom Codec Selection and Enable an Independent Call Path; 6.4 Key Issues: Replacing the Voice Circuit with VoIP; Chapter 7: Replacing Call Signaling with VoIP; 7.1 VoIP Signaling Protocols; 7.2 H.323; 7.3 SIP; 7.4 IAX; 7.5 MGCP; 7.6 Cisco SCCP; 7.7 Heterogeneous Signaling; 7.8 Key Issues: Replacing Call Signaling with VoIP; Chapter 8: VoIP Readiness; 8.1 Assessing VoIP Readiness; 8.2 Business Environment; 8.3 Network Environment; 8.4 Implementation Plan; 8.5 Key Issues: VoIP Readiness; Chapter 9: Quality of Service; 9.1 QoS Past and Present; 9.2 Latency, Packet Loss, and Jitter; 9.3 CoS; 9.4 802.1q VLAN; 9.5 Quality of Service; 9.6 Residential QoS; 9.7 Voice QoS on Windows; 9.8 Best Practices for Quality of Service; 9.9 Key Issues: Quality of Service; Chapter 10: Security and Monitoring; 10.1 Security in Traditional Telephony; 10.2 Security for IP Telephony; 10.3 Access Control; 10.4 Software Maintenance and Hardening; 10.5 Intrusion Prevention and Monitoring; 10.6 Project 10.3. Logging and Controlling VoIP Packets with iptables; 10.7 Key Issues: Security and Monitoring; Chapter 11: Troubleshooting Tools; 11.1 VoIP Troubleshooting Tools; 11.2 The Three Things You'll Troubleshoot; 11.3 SIP Packet Inspection; 11.4 Interoperability; 11.5 Project 11.3. Trace Both Ends of a Call Setup with Log Comparison; 11.6 When, Not if, You Have Problems...; 11.7 Simulating Media Loads; 11.8 Key Issues: Troubleshooting Tools; Chapter 12: PSTN Trunks; 12.1 Dial-Tone Trunks; 12.2 Routing PSTN Calls at Connect Points; 12.3 Timing Trunk Transitions; 12.4 Key Issues: PSTN Trunks; Chapter 13: Network Infrastructure for VoIP; 13.1 Legacy Trunks; 13.2 VoIP Trunks; 13.3 Project 13.1 Use Dial-Plan to Connect to Multiple VoIP Networks; 13.4 WAN Design; 13.5 Disaster Survivability; 13.6 Metro-Area Links; 13.7 Firewall Issues; 13.8 Peer-by-Peer Codec Selection; 13.9 Project 13.2. Build an Interactive Directory on a SIP Display Phone; 13.10 Key Issues: Network Infrastructure for VoIP; Chapter 14: Traditional Apps on the Converged Network; 14.1 Fax and Modems; 14.2 Fire and Burglary Systems; 14.3 Surveillance Systems and Videoconferencing; 14.4 Voice Mail and IVR; 14.5 Emergency Dispatch/911; 14.6 Key Issues: Traditional Apps on the Converged Network; Chapter 15: What Can Go Wrong?; 15.1 Common Problem Situations; 15.2 Key Issues: What Can Go Wrong?; Chapter 16: VoIP Vendors and Services; 16.1 Softphones and Instant Messaging Software; 16.2 Skype; 16.3 Other Desktop Telephony Software; 16.4 Developer Tools and SoftPBX Systems; 16.5 VoIP Service Providers; 16.6 Telephony Hardware Vendors; Chapter 17: Asterisk Reference; 17.1 How Asterisk Is Supported; 17.2 Asterisk's Configuration Files; 17.3 Asteriskdial-planAsterisk Dial-Plan; 17.4 AsteriskchannelsAsterisk Channels; 17.5 The Asterisk CLI; 17.6 Integrating Asterisk with Other Software; 17.7 Key Issues: Asterisk Reference; Appendix A: SIP Methods and Responses; Appendix B: AGI Commands; Appendix C: Asterisk Manager Socket API Syntax; Glossary; Colophon;