 as e-mail, Telnet, FTP, and the World Wide Web, are referred to as elastic applications because they are tolerant of net- work delays and packet losses. Unlike those applications, advanced real-time appli- cations are highly sensitive to timely data delivery. Quality of service (QoS) is the most important obstacle for the Internet and IP networks to overcome, especially in light of the growing use of voice and video. As QoS emerges within the Internet, the ability to differentiate services will result in differentiated pricing. QoS capabil- ities will allow revenue-generating service levels to be implemented and service- level agreements (SLAs) to be negotiated. The ability to control and manage a network effectively will allow the creation of value-added services and packages. Providing value-added IP services implies increased attention to tools and equipment that help service providers succeed. These include software that gives service providers greater network control and visibility; intrusion prevention systems that support always-on stateful inspection (i.e., a form of stateful inspection that provides cumulative data against which sub- sequent communication attempts can be evaluated and acted on in real-time) and deep packet analysis capabilities; software that can deliver flexible bandwidth; tools that offer granular analysis of bandwidth consumption by customers; and tools that enable creative solutions that reduce costs, such as the robots from CityNet Tele- communications (www.citynettelecom.com) that string fiber through sewers at a fraction of the cost of digging up city streets to lay the fiber. Value-added IP services allow carriers greater differentiation from their com- petitors. Evolving next-generation IP services include IP virtual private networks (VPNs), IP telephony (IPT) and Voice over IP (VoIP), IP centrex and IP call cen- ters, application hosting, mobility management/follow-me services, unified mes- saging, instant messaging (IM), presence management, Video over IP, IP television (IPTV