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Deterministic Service Guarantees in 802.12 Networks, Part I : The Single Hub Case
Keyword(s): quality of service; LAN; deterministic services
Abstract: In this paper in its sequel  we study the problem of allocating resources in single hub and cascaded 802.12 networks. We show that the use of the 802.12 high priority mechanism when combined with admission control, allows the network to provide small, deterministic delay bounds in large, cascaded network topologies with potentially many hundreds of nodes. The allocation scheme proposed is based on a time frame concept that takes advantage of the properties of the Demand Priority medium access protocol to provide much tighter delay bounds than given by the time frame itself. The first part of the work is to analyse relevant network performance parameters and their dependencies. In the second part, we describe the scheduling model and define the admission control conditions used to provide deterministic service guarantees. Experimental results received with a UNIX kernel based implementation in a standard 802.12 test network confirm our theoretical results for network parameters, throughput and delay bounds. In this paper, the single hub topology is analysed. In the sequel of this paper, the network parameters are derived for cascaded 802.12 networks which allow the admission control conditions to be applied to the topologies.
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