rging for calls belongs to the last century. Skype software gives people new power to affordably stay in touch with their friends and family by taking advantage of their technology and connectivity invest- ments. -Niklas Zennstrom, CEO & cofounder of Skype Many readers will recall KaZaA, the file sharing program that became well known during the turbulent Napster controversy over the unautho- rized sharing of commercial music. The same two programmers who cre- ated KaZaA, Niklas Zennstrom and Janus Friis, put their heads together and concluded that while peer-to-peer music works well, it is fraught with legal ramifications. So what else could be shared in a peer-to-peer fashion? Voice. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Telephony Chapter 3 To date, more than 45 million people have downloded the free Skype installer, and as I sit here writing this section in mid-December 2004 there are 1.6 million people online. I have used Skype for over a year and the service is excellent. The only downside is that the original, free Skype is a walled-garden technology-users can only talk with other Skype users. But with over a million people online at any time, and with the application's ability to search for other users by city and country, you'll find someone to talk with. Skype also supports messenging and video- conferencing. Of course, the walled-garden concept is limiting, so in early 2004 Skype announced SkypeOut, a paid service that allows Skype users to place calls to regular telephones in about 20 countries (and growing) for about two cents per minute. Vonage and Skype are but two of the growing herd of public VoIP providers that are redefining the world of voice services. In the enter- prise space, VoIP is having an equally dramatic impact. Let's examine the various ways in which enterprise VoIP can be deployed to the bene- fit of c