Gigabit networking
On the Use of Quality of Service in IP over ATM
On the Use of Quality of Service in IP over ATM
The Journal of Supercomputing
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An 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 quality-of-service (QoS) guarantees for internet traffic running through ATM subnets. This paper describes a priority scheme, named User Priority, for providing an IP integrated service with QoS over ATM switched virtual circuits (SVCs) to obtain better performance of packet delivery. The User Priority is defined as a three-bit field which uses a type of service (TOS) field in the IP datagram header. This yields eight different service classes with a value of 7 for the highest priority and 0 for the lowest priority. Class 6 and 7 services are for real-time traffic and have their own VCs. Packets with Classes 0 through 5 are sent an 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 to be implemented on the end systems that want to take advantage of them.