Student: Gung-Chou Lai Advisor: Ruay-Shiung Chang

Institute of Information Management

National Taiwan University of Science and Technology

Integrated Service Internet running real-time and multimedia applications is rapidly becoming a reality. Meanwhile, ATM technology is appearing in the marketplace. It is an important problem to integrate ATM networks into this Integrated Service Internet. One of the approaches, classical IP over ATM, is now widely deployed, effectively solving the problem of internetworking and interoperability. A key remaining issue is to provide the QoS guarantees for Internet traffic running through ATM subnets. This paper describes a priority scheme, named User Priority, for providing IP Integrated Service with quality-of-service over ATM switched virtual circuits (SVCs) to get better performance of packet delivery.

Define the User Priority as a three-bit field which uses Type of Service (TOS) field in the IP datagram header. This yields 8 different service classes with value 7 = highest priority and 0 = lowest priority. Class 6 and Class 7 services are for real-time traffics and have their own VCs. Packets with Class 0 through 5 are sent on aggregate VC. This method is different from the IP-over-ATM scheme where only one VC is set up between two communicating IP hosts. Thus, packets can be treated differently according to their priorities such that they can enjoy the various QoS guarantees provided by ATM networks. It is backward compatible with existing IP implementations. These newer options need only be implemented on the end systems that want to take advantage of them.