The development and use of distributed multimedia applications are growing rapidly. Also, multimedia applications on the Internet commonly employ the UDP transport protocol, which lacks a congestion control mechanism. Moreover, the resource allocation is based on initial availability of resources and does not take into account changes in availability during an ongoing transmission.
Many multimedia applications are long-lived, exacerbating the problem.
Users of rate-adaptive applications do not have any incentive to scale back their sending rate below their access bandwidth, since selfish users will generally obtain better quality than those that reduce their rate. Pricing network services based on the level of service, usage, and congestion provides a natural and equitable incentive for applications to adapt their sending rates according to network conditions. Increasing the price during congestion gives the application an incentive to back-off its sending rate and at the same time allows an application with more stringent bandwidth and QoS requirements to maintain a high quality by paying more. The customer and network negotiate and agree upon specifications such as the type of service user packets will receive, the constraints the user traffic must adhere to, and the price to be charged for the service. It should allow the service provider to communicate service availability, estimated prices for available services and charges accruing to the user, and allow the user to request a specific service.