This "Introduction to IP Telephony" book explains why companies are converting some or all of their telephone systems from dedicated telephone systems (such as PBX) to more standard IP telephony systems. These conversions allow for telephone bill cost reduction, increased ability to control telephone services, and the addition of new telephone information services. By upgrading their systems, companies can immediately reduce their telecommunication costs 40% to 70%. Because IP telephony systems allow the end user and system administrators to setup and disconnect telephone numbers and services, this provides increased control over their telephone features and services. IP telephony is usually based on standard data formats (Internet Protocol). This permits information systems (such as product catalog information) to be more easily linked to the telephone system, thus providing the ability for companies to increase sales through interactive telephone and Internet order processing systems. You will learn that not all voice over data IP telephony systems and services are the same. There are cost and quality tradeoffs along with common problem areas and risks. There are many ways these systems can reduce telecommunication costs along with the ability to create new revenue producing services. You will understand how you can get better than telephone toll quality audio, how to maintain or increase system reliability, and new ways to use intelligent telephone systems to increase company revenues. You will learn how employees can keep their phone numbers and existing equipment (using adapters) and call anywhere in the world using IP telephony services. Discover how you can get one (or several) international telephone numbers so your customers can use a local telephone number to call you when you are in another country. You will learn how voice over data telephone service usually allows you to setup new telephone services instantly, display your accounting records and bills in real time, and allow you to integrate information systems (such as sales systems) with your telephone networks. This book explains the basics of how voice over data telephone service works. This includes how the different ways that voice signals can be converted to data signals (not all of them are the same) and how the conversion process can affect your voice quality. Discussed are the basic processes of sending packets through a data network (such as the Internet) and how the losses of packets (and some do get lost) do not usually affect the voice quality. You will be introduced to the different types of voice over data communication systems that are used for company communication networks. This includes public Internet telephone services providers (ITSPs), IP Centrex service providers, and IP private branch exchange (iPBX) systems. Also covered are the functional types of IP telephony network equipment such as gateways that are used in voice over data network and some key issues to consider when deploying VoIP systems. This will help you to understand the different types of servers including proxy servers, redirect servers, access control, provisioning, and policy servers. You will learn about telephone number portability. Next you will learn about the quality of service (QoS), security, and reliability you can expect from voice over data telephone systems and services. Find out how you can get guaranteed toll quality service with some voice over data telephone systems and why you may experience echoes and audio distortion on others. Learn about how secure your connections are and the different forms of security including the control of physical access, authentication checks, and data encryption. Understand how to maximize the reliability of your calls by understanding the reliability of different parts of the network. Finally, you will discover some of the advanced features and services that are possible with Internet telephone service that is not possible with most traditional telephone systems. This includes unified messaging, ways to connect telephone extension anywhere in the world, how you can setup one (or many) global telephone numbers that will ring to your IP telephone without international charges. Learn how voice over data telephone service allows you to share notes, pictures, and files using a whiteboard while you are talking for interactive web seminars (Webinars). If you are considering converting some of your telephone systems and services be able to use IP telephony services or you just want to know more about the options and advantages of IP telephony services, this is book is a great introduction.