Chapter 1: Working with VoIP

Cisco Press

Cover image 

Excerpt from Voice over IP Security.

By Patrick Park

Published by Cisco Press

ISBN-10: 1-58705-469-8

ISBN-13: 978-1-58705-469-3

This chapter covers VoIP strengths and vulnerabilities with the following topics:

  • VoIP advantages

  • VoIP disadvantages

  • Sources of vulnerability

  • Vulnerable components

  • Myths versus reality

Voice over Internet Protocol (VoIP) has been prevailing in the telecommunication world since its emergence in the late 90s as a new technology transporting multimedia over the IP network. It is very common today for people to make phone calls with IP phones or client software (for example, Skype, iChat, and Google Talk) on their computer. Many telecommunications companies and other organizations have been moving their telephony infrastructure to their data networks, because it provides a cheaper and clearer alternative to traditional public service telephone network (PSTN) phone lines.

Even though the VoIP service is getting popular, its technology is still developing. It is growing rapidly throughout North America and Europe, but it is sometimes awkwardly implemented on most legacy networks, and often lacks compatibility and continuity with existing systems. Nevertheless, VoIP will capture a significant portion of the telephony market, given the fiscal savings and flexibility that it can provide.

The context of VoIP service in this book includes not only voice, but also video, Instant Messaging (IM), presence data, and fax data over the IP network. Figure 1-1 shows VoIP service architecture with many different types of services.

In this chapter, you learn about the benefits and disadvantages of using VoIP, its vulnerabilities and components, and this chapter also dispels some myths. The content in this chapter refers to recommendations from the National Institute of Standards and Technology (NIST).1


Note - This chapter approaches the topics at a high level. The technical details are described in Part II, "VoIP Security Best Practices."


Like every technology, VoIP has many benefits and disadvantages. The following section describes the benefits of VoIP.

Figure 1-1

VoIP Service Architecture

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