Preemption-based admission control in multimedia multiparty communications

In multimedia, multiparty communications a typical participant receives and often generates multiple real-time streams. Network resources are dedicated to each stream and are dynamically allocated and released in response to changing users demands throughout the session. Admission control procedures, which prioritize users' requests for stream delivery, and decide which resources to allocate, are considered. Existing admission control schemes base their decisions on resources that are unused at the time of the request, and reject a request (or queue it) if there are insufficient unused resources. The paper presents a novel approach in which admission is based not only on the unused resources but also on the resources occupied by the streams that are currently received by the requestor. If sufficient unused resources to deliver a requested stream are not available, other streams that are delivered to the requestor are preempted and the resources they occupy are reallocated to satisfy the new request. The manner by which candidate streams for preemption are identified and resources are reallocated depends on the relative importance of the streams to the recipient and the topology of the paths leading to it. The effect of the routing used by the network on the topology of the paths leading to a multi-stream receiver is discussed and protocols for preemption-based reallocation are presented.