ssurance levels and support for AAA. 1.2 Moving to Packets There are two distinct global networks today: the PSTN (Public Switched Telephone Network) and Internet. The PSTN is based on the concept of circuit switching in which a dedicated connection/call is setup dynamically between a source and destination for the duration of the call. An advantage of circuit switched networks is that they allow data to be transferred with guaranteed transmission capacity, thus providing support for real-time traffic. However, this connection consumes network resources for the entire duration, even when no information is being transferred. The Internet is built on the concept of packet switching - basically moving IP packets from source to destination in a best effort, connection-less manner. The data is broken up into packets and each packet is individually routed through the network. While the world of PSTN circuit switching was developed and optimized for voice communication, the packet switching Internet was essentially developed for carrying data traffic. Other packet/cell technologies, such as Frame Relay and ATM, were invented to fulfill the need for private networks and served as the technology for building backbone data networks. FR and ATM based networks are packet-based but connection-oriented. In these networks, a path through the network - often referred to as a logical channel or virtual circuit - is established when data transfer begins. Such connection-oriented packet networks can guarantee network resources for the duration of the connection Chapter 8 - Next-Generation OSS and hence were considered ideal for implementing Quality of Service (QoS) and for carrying both voice and data. Today, the biggest disadvantage of IP-based technology - no guarantee of QoS - has been overcome with new IP-based standards such as MPLS and has essentially blurred the distinction between traditional IP based networks and ATM/FR based networks. When Internet access became prevalent, dial-up was the preferred access method as a user