s such as Skype and Google are often referred to as over-the-top (OTT) providers because their services are deployed over cable TV and the cabling infra- structure of incumbent telephone companies. These providers own VoIP hardware and software but not the cabling over which the signals travel. Calls are routed from users' computers to cable TV or incumbent telephone company broadband circuits. From there, they are routed over the Internet for calls to other users with the same provider, or they are routed to the PSTN. For calls to the PSTN, Session Border Controllers (SBCs) convert VoIP protocols to those compatible with the PSTN, and vice versa. OTT providers include Google, Skype, magicJack, and Vonage. Figure 5-1 presents an example of how these calls are routed. With the exception of Google's service, which is accessed from within browsers, most VoIP services require additional computer software and/or hardware at the cus- tomer location. The Vonage service requires an external device into which a telephone is plugged. The external device, a terminal adapter, converts the analog voice signals to those compatible with the Internet, and vice versa. Most of these providers earn revenue from monthly fees, ads on their site, and adjunct hardware sold on their sites. In contrast, magicJack's revenue is derived in large part from ads on its site and from fees other phone companies pay to the company. This is because magicJack is registered with the United States government as a telephone company. This enables it to collect access fees from all carriers whose customers call magicJack's customers over the PSTN. Telephone companies charge one another access fees for carrying one another's calls between local carriers and long-distance networks on the PSTN. For example, magicJack charges access fees to all telephone companies for each call its customers place to magicJack's customers. VolP Calling Services over Broadband SBC converts Internet between PSTN and VolP protocols Telco or cable VolP server company network Ca