ustomers. VoIP Implementation IP voice has become a reasonable technological alternative to traditional PCM voice. VoIP gateways are in the late stages of development with regard to reliability, features, and manageability. Consequently, service providers wishing to deploy VoIP solutions have a number of options available to them. One is to accept the current state of the technology and deploy it today, while waiting for enhanced versions to arrive, know- ing that while the product may not be 100 percent carrier grade, it will certainly be an acceptable solution. A second option is a variation of the first: Implement the technology that is available today, but make no guarantees of service quality. This approach is currently being used in Western Europe and in some parts of the United States as a way to provide low-cost long-distance service. The service is actually quite good, and while it is not "toll quality," it is inex- pensive. And since most telephony users have become inured to the lower than toll quality of cellular service, they are less inclined to be annoyed by VoIP service that is lower than they might have otherwise antici- pated. Needless to say this works in the favor of the VoIP service 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 Telephony provider. Furthermore, the companies deploying the service often have no complex billing infrastructure to support because they rely on prepaid billing models, thus they can keep their costs low. SkypeOut, for example, allows subscribers to buy credit online using a credit card. Carrier Class IP Voice There is no question that VoIP is here to stay and is a serious contender for voice services in both the residence and enterprise markets. The dol- lars don't lie: Domestic revenues for VoIP will grow exponentially between 2004 and 2009, from $600 million today to $3 billion. Fr