Preface


Voice over IP is a family of technologies that has sweeping implications for everybody who uses telephones, the Internet, fax machines, email, and the Web. VoIP borrows from, and enhances, many disciplines of communications technology; it promises to revolutionize the most familiar of these technologies, the telephone. The Internet Protocol, analog telephony, digital telephony and T1 circuits, digital audio signal processing, high-availability networking, and a host of other concerns are all touched by growing borders of the vast, ambitious realm of VoIP.

VoIP has found its way into business phone systems, desktop messaging software, and residential telephony service. Your mortgage or insurance company's web site may offer you the ability to communicate by VoIP with a customer service rep using your computer. You may subscribe to VoIP-based telephone services like Packet8, AT&T CallVantage, Vonage, or Broadvox Direct as a replacement for your old, traditional phone service.

In the late 1990s, VoIP was lauded as a way to save on long-distance charges by calling Grandma and Grandpa using a PC with a headset and a microphone. But today's definition of VoIP is far broader. Hundreds of thousands of VoIP-based devices are in use in the United States, and fast-growing shipments of VoIP-compatible telephone systems have revitalized the data networking industry. The next evolutionary step for the Internet is to become reliable enough to replace the global telephone network as we know it.

So, VoIP is a disruptive technology family that promises to revolutionize the way we communicate, while driving decreases in the cost of that communication and increases in the speed, reliability, and availability of the Internet itself. That's what VoIP does . But you're reading this book because you want to know how it does it. Here's what you'll encounter while reading Switching to VoIP :

  • A definition of public and private legacy voice systems and a quick review of their evolution

  • A description of the core technologies of digital telephonysampling, pulse code modulation, time division multiplexing, trunking, and call signaling

  • Examples of how VoIP networks overlay IP networks and how voice applications reside within the OSI network model

  • An explanation of why many early VoIP adopters' implementations didn't live up to expectations

  • An introduction to the two subsets of VoIP standards: audio transmission and signaling

  • Introductions to SIP, H.323, and other signaling specifications that are commonly used in IP telephony

  • Some practical strategies for justifying VoIP adoption in a business scenario

  • An introduction to IP hardphones, analog telephone adapters, softPBX servers, and the other devices that make VoIP systems tick

  • Strategies for dealing with quality-of-service issues, including policy-based, protocol-based, and practice-based approaches to ensuring tip-top operational quality of a VoIP network

  • Information about interfacing VoIP systems with traditional phone equipment and the public telephone system by way of analog trunks and T1 lines

  • The basics of enforcing low-layer security in a VoIP environment, with examples for IP Tables firewalls

  • Tips for gauging VoIP readiness on an enterprise network or over an Internet pathway

  • Scenarios that describe what network technologies work best for voice systems, and how to compensate with quality-of-service measures across those that don't work so well for voice

  • Dozens of practical, hands-on projects that you can use to build the pieces of your VoIP network while learning which standards and practices will work best for your particular environment

  • A number of troubleshooting scenarios to help you deal with, and avoid, the most common mistakes that are made when implementing this technology

  • A handy vendor reference that will put you in touch with the key software, hardware, and service players in the VoIP business

  • A reference for the basic configuration, SIP interfacing, and legacy interfacing of the world's most popular open source telephone server, Asterisk



Switching to VoIP
Switching to VoIP
ISBN: 0596008686
EAN: 2147483647
Year: 2005
Pages: 172

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