The Internet has nearly a ten year history as a global, public communication infrastructure. The two applications that have created the demand from private and business users have been the World-Wide Web and electronic mail. We have inthelast?veyearsseentherapidlyemergingpopularityofpeer-to-peersharing of ?les, mostly for music, and to a more limited extent also the introduction of Internet telephony, television, and radio. These services place demands on the infrastructure that are higher with respect to quality and connectivity than web sur?ng and e-mail. Mobile (cellular) telephony has...