A head-of-line approximation to delay-dependent scheduling in integrated packet-switched networks

Abstract

Packet switching is one means of providing integrated voice/data communications. Voice packets have a finite lifetime, representing the time between packet generation and playback. Ifapacket misses its playback time, it is dropped, degrading customer speech quality. The chief cause of packet loss is the variability of end-to-end delay due to queueing at intermediate nodes. The queueing discipline used within the network directly affects this delay variance. In an integrated environment, scheduling must provide adequate performance for all classes. We first used simulation to compare the performance of several queueing disciplines for trunk scheduling at a packet switch with only voice traffic. A delay-dependent priority scheme, the Budgeted Residual-Life Dependent Discipline (BURD), resulted in the lowest packet loss rate at the node. We then used BURD and a Head-Of-Line discipline to construct scheduling policies for networks with integrated traffic. We found it was possible to approximate the performance of the delay-dependent priority schemes using more easily implemented Head-of-Line schemes and still provide adequate service for data traffic.

An evaluation of scheduling mechanisms for providing best-effort real-time communications in wide-area networks

“…Thus, packets tend to be "compensated" by a higher priority for above-average delays suffered at earlier nodes. This policy is identical to the "Budgeted Residual-Life Dependent Discipline" (BURD) in [15], developed independently of our HL policy [le].…”

Deadline-based scheduling in support of real-time data delivery

“…In [9], a simulation study was conducted to compare the performance of FCFS and the following two channel scheduling algorithms:…”

“…It was found that DDV yields the best performance in terms of the percentage of voice packets that are delivered on-time, and HOLV has comparable performance [9].…”

“…We will refer to this algorithm as T/H. T/H has also been studied in the context of packet-switched networks [9,10,11].…”

Real-time data delivery for multimedia networks

“…The Asynchronous Transfer Mode (ATM) is considered for use with multimedia traffic due to its ability to dynamically allocate bandwidth [7,16]. Other recent work in providing real-time guarantees for multimedia traffic includes support for FDDI networks [10] and packet switched networks [8,6].…”