A programming interface for network resource management

The deployment of advanced network services such as virtual reality games, distributed simulation, and video conferencing, will require sophisticated resource management support. The reason is that the quality of the delivered service will depend both on what resources are allocated to the user, and how these resources are managed at runtime. This problem is challenging because the definition of Quality of Service (QoS) is in general user specific, so hardwired resource management mechanisms will not be sufficient. To address the runtime resource management problem, we introduce the concept of a delegate, a code segment that applications or service providers inject into the network to assist in the management of the network resources that are allocated to them. This approach allows users to tailor runtime resource management to best meet their specific needs. Moreover, since delegates execute inside the network, they can easily collect information on changing network conditions, and can quickly adapt the resource allocations for the flows they are responsible for. Delegates have been implemented in the CMU Darwin system, which provides an integrated set of customizable resource management mechanisms in support of sophisticated network services. In this paper we present the design of the delegate runtime system, focusing on the programming interface that delegates use to monitor the network and modify resource use. We describe how delegates are supported in Darwin, and we show how delegates can be used to deal with a number of problems such as congestion control for video streaming, tracking down non-adaptive sources, and balancing traffic load.