cs6235-ratematch_kangli - 1 A Rate-Matching Packet...

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Unformatted text preview: 1 A Rate-Matching Packet Scheduler for Real-Rate Applications Kang Li, Jonathan Walpole, Dylan McNamee, Calton Pu and David C. Steere * Department of Computer Science and Engineering Oregon Graduate Institute {kangli, walpole, dylan, calton, dcs}@cse.ogi.edu Abstract A packet scheduler is an operating system component that controls the allocation of network interface bandwidth to outgoing network flows. By deciding which packet to send next, packet schedulers not only determine how bandwidth is shared among flows, but also play a key role in determining the rate and timing behavior of individual flows. The recent explosion of rate and timing-sensitive flows, particularly in the context of multimedia applications, has focused new interest on packet schedulers. Next generation packet schedulers must not only ensure separation among flows and meet real-time performance constraints, they must also support dynamic fine-grain reallocation of bandwidth for flows with variable-bit-rate requirements. Unfortunately, todays packet schedulers either do not support rate and timing sensitive flows, or do so with reservation systems that are relatively coarse-grain and inflexible. This paper makes two contributions. First it shows how bandwidth requirements can be inferred directly from real-rate flows, without requiring explicit specifica- tions from the application. Second, it presents the design, implementation and per- formance evaluation of a rate-matching packet scheduler that uses these inferred requirements to automatically and dynamically control the bandwidth allocation to flows. 1. Introduction A packet scheduler is an operating system component that allocates the limited bandwidth of an outgoing network interface among competing flows. It manages interface buffers and controls which packet to send next. As the Internet evolves, applications such as Internet streaming video players that generate multime- dia network flows, are expected to be widely supported. These applications are timing sensitive, and they require packet schedulers to support isolation among flows and allocate the right amount of bandwidth to meet their timing-constraints. Todays packet schedulers either isolate timing sensitive flows from bursty ones by using priority schemes [3, 13], or they implement coarse-grain sharing of the bandwidth among competing flows using reserva- tions [5, 6, 10 and 15]. Unfortunately, priority schemes do not take into account the timing requirements of the individual flow. Reservation-based schedulers do take timing requirements into account, but do not generally support fine-grain dynamic readjustments of reservations. The consequence of using static reser- vations is that bandwidth must be over-reserved based on the worst case requirement, which can cause sig- nificant inefficiency when variable bit-rate flows are present....
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This note was uploaded on 10/10/2010 for the course CS 6235 taught by Professor Staff during the Fall '08 term at Georgia Institute of Technology.

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cs6235-ratematch_kangli - 1 A Rate-Matching Packet...

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