nternet Service Provider (ISP). The advantage of a packet-based approach is that GPRS uses the medium (in this case, the radio link) only as long as data is being sent or received. Mul- tiple users can share the same radio channel very efficiently. In contrast, with current circuit-switched connections, users have dedicated connections during their entire call, even if they are not sending data. Many applica- tions have idle periods during a session. With packet data, users will only pay for the amount of data they actually communicate, and not the idle time. In fact, with GPRS, users could be "virtually" connected for hours at a time and only incur modest connect charges. Although packet-based communications works well with all types of communications, it is especially well suited for frequent transmission of small amounts of data. We refer to this as short and bursty, such as real- time e-mail and dispatch (vehicles and field service). Packet is equally well suited for large batch operations and other applications involving large file transfers. However, when using large file transfers, the cost can become very expensive compared to circuit-switched data transmissions. GPRS supports the IP as well as the X.25 protocol. IP support is increasingly more important as companies look to the Internet as a way for their remote work- ers to access corporate intranets. This is true when using a Virtual Private Network (VPN). In the case of VPNs, GPRS works well because of its GPRS Tunneling Protocol (GTP), which can secure the mobile data while in tran- sit on the wireless networks, and IPSec transfers can be used when tran- siting the wireline networks. UMTS is a European Telecommunications Standards Institute (ETSI) term for a 3G mobile telecommunication service. Over recent years, mobile telephony evolutions have become known as the following categories. First Generation (1G) In the early 1980s, the first-generation (1G) technologies were the world's first public mobile telephone services such as the Advanced Mobile P