Implicit admission control for a differentiated services network

Admission control is a crucial network element for providing quality of service (QoS) guarantees in the Internet. In this paper, we propose a novel framework approach, called implicit admission control (iAC), for admission control in a differentiated services (DiffServ) network. In the iAC approach, admission control is performed distributedly at routers. No signaling is needed for exchanging service and traffic information between flows and routers. The service requirement and some coarse traffic information of a flow are carried by packets of the flow. Specifically, the DiffServ field is utilized for this purpose. At each router, admission control for the flow is performed when its first packet is detected. The admission test is based on the service requirement and traffic information carried by the DiffServ field of the packet, as well as the local traffic and resource information. In addition, to simplify admission control, two flow aggregation methods are adopted at each router. One is link-based fair aggregation (LBFA) for the deterministic expedited forwarding (EF) service. The other is dynamic priority based flow aggregation (DPFA) for the statistical assured forwarding (AF) service. Analytical results show that with these flow aggregation approaches, a newly admitted flow does not adversely affect QoS guarantees of existing flows. Consequently, admission test is needed only for the new flow.