Traffic contract: key to orderly use, provisioning, and charging of ATM services

A customer and a network operator need to establish a service contract for the customer to use an ATM transport service being provided by the network operator. This paper aims to indicate that a well-defined traffic contract is a key to the orderly use, provisioning, and charging of ATM services. Based on the traffic contract, the user needs to shape its traffic, and the network operator polices the traffic, guarantees the QoS, and charges the customer for the transport service delivered. A traffic contract for an on-off source with peak rate and expected mean rate as traffic descriptors is widely used in the literature. Such a traffic contract poses problems to a network operator due to the unspecified burst size and the declaration of only the expected mean rate. The charging schemes for such a traffic contract, as proposed in the literature, consider an element of charge penalty to the customer if the actual mean rate differs from the expected mean rate. This makes life difficult for a user because the actual mean rate is difficult to predict for on-line applications. This paper attempts to solve the above problems for a network operator by using a strict traffic contract with well-defined traffic descriptors and methods for conformance checking as proposed by the ATM Forum. An element of bandwidth parameter renegotiation is introduced to allow the user predict the bandwidth requirements more accurately for relatively short time periods. These concepts are illustrated with the help of example traffic contracts for a variable bit-rate MPG-2-encoded video stream.