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cs6235- - Real-Time Systems 24 171202 2003...

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Real-Time Systems, 24, 171±202, 2003 # 2003 Kluwer Academic Publishers. Manufactured in The Netherlands. Utilization-Based Admission Control for Scalable Real-Time Communication BYUNG-KYU CHOI [email protected] Department of Computer Science, Michigan Technological University, Houghton, MI 49931-1295, USA DONG XUAN [email protected] Department of Computer and Information Science, The Ohio State University, Columbus, OH 43210-1277, USA RICCARDO BETTATI [email protected] Department of Computer Science, Texas A&M University, College Station, TX 77843-3112, USA WEI ZHAO [email protected] Department of Computer Science, Texas A&M University, College Station, TX 77843-3112, USA CHENGZHI LI [email protected] Department of Computer Science, University of Virginia, Charlottesville, VA 22904-4740, USA Abstract. We propose a utilization-based schedulability and admission control mechanism for distributed systems with workload aggregation to achieve scalability. We use the differentiated services ( diffserv ) architecture to describe and illustrate our approach. Scalability of admission control is achieved by determining off-line safe levels of server utilization. Scalability during the connection lifetimes is provided by the aggregation mechanisms (for example, class-based scheduling) provided by the diffserv architecture. Our evaluations show that our system's admission probabilities are very close to those of signi®cantly more expensive approaches, which do not allow for workload aggregation. At the same time, admission control overhead during ¯ow establishment is very low. Keywords: admission control, end-to-end deadlines, schedulable utilization, QoS guarantees, and differentiated services 1. Introduction This paper presents a methodology to apply utilization-based admission control to provide hard real-time communication in a scalable fashion. By hard real-time we mean that packets are delivered from their sources to the destinations within their end-to-end deadlines. Packets delivered beyond their end-to-end deadlines are considered useless. By scalable we mean that we want to support a large number (say, many thousands) of connections over a network with many nodes (in our context nodes are switches or routers), while at the same time allowing for high resource utilization. The integrated services (IS) architecture of the IETF (Braden et al., 1994) is a good example to illustrate the types of problems encountered in admission control for large systems. In IS, each connection is strictly controlled both by admission control at connection establishment time and by packet scheduling during the lifetime of the connection. At establishment time, the necessary resources for the new connection are
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allocated, and during the lifetime, the connection is policed to ensure that abnormal behavior of a connection does not affect other connections. This necessitates that information about every connection is kept by each node along the path for admission control and packet forwarding purposes.
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cs6235- - Real-Time Systems 24 171202 2003...

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