2 Analysis of Internet Services

he increasing demand for Internet services is spurring the deployment of high-speed IP back-bones, but the specific network technology to be used still remains an open issue. One of the main advantages of asyn-chronous transfer mode (ATM) networks is the capability to provide dynamic resource allocation for video, voice, and data, thus making ATM ideally suited for the high variability of IP traffic. However, the state of the art in ATM equipment reveals that only limited capabilities are provided for such dynamic resource allocation. Indeed, most ATM network operators pro-vide constant bit rate (CBR) and best effort (unspecified bit rate, UBR) end-to-end virtual circuits (VCs) only. While the CBR service class offers static allocation of resources, UBR serves the purpose of best-effort transport of ATM cells. Since the best-effort paradigm is commonly used for the mos