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35
Buffer overflow management in QoS switches
 SIAM Journal on Computing
, 2001
"... Abstract. We consider two types of buffering policies that are used in network switches supporting Quality of Service (QoS). In the FIFO type, packets must be transmitted in the order in which they arrive; the constraint in this case is the limited buffer space. In the boundeddelay type, each packe ..."
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Cited by 78 (13 self)
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Abstract. We consider two types of buffering policies that are used in network switches supporting Quality of Service (QoS). In the FIFO type, packets must be transmitted in the order in which they arrive; the constraint in this case is the limited buffer space. In the boundeddelay type, each packet has a maximum delay time by which it must be transmitted, or otherwise it is lost. We study the case of overloads resulting in packet loss. In our model, each packet has an intrinsic value, and the goal is to maximize the total value of transmitted packets. Our main contribution is a thorough investigation of some natural greedy algorithms in various models. For the FIFO model we prove tight bounds on the competitive ratio of the greedy algorithm that discards packets with the lowest value when an overflow occurs. We also prove that the greedy algorithm that drops the earliest packets among all lowvalue packets is the best greedy algorithm. This algorithm can be as much as 1.5 times better than the taildrop greedy policy, which drops the latest lowestvalue packets. In the boundeddelay model we show that the competitive ratio of any online algorithm for a uniform boundeddelay buffer is bounded away from 1, independent of the delay size. We analyze the greedy algorithm in the general case and in three special cases: delay bound 2, link bandwidth 1, and only two possible packet values. Finally, we consider the offline scenario. We give efficient optimal algorithms and study the relation between the boundeddelay and FIFO models in this case.
Approximating the Throughput of Multiple Machines in RealTime Scheduling
"... We consider the following fundamental scheduling problem. The input to the problem consists of n jobs and k machines. Each of the jobs is associated with a release time, a deadline, a weight, and a processing time on each of the machines. The goal is to find a schedule that maximizes the weight of j ..."
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Cited by 75 (7 self)
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We consider the following fundamental scheduling problem. The input to the problem consists of n jobs and k machines. Each of the jobs is associated with a release time, a deadline, a weight, and a processing time on each of the machines. The goal is to find a schedule that maximizes the weight of jobs that meet their deadline. We give constant factor approximation algorithms for four variants of the problem, depending on the type of the machines (identical vs. unrelated), and the weight of the jobs (identical vs. arbitrary). All these variants are known to be NPHard, and we observe that the two variants involving unrelated machines are also MAXSNP hard. To the best of our knowledge, these are the first approximation algorithms for such problems in the nonpreemptive o line setting. The specific results obtained are:  For identical job weights and unrelated machines: a greedy 2approximation algorithm.  For identical job weights and k identical machines: the same greedy alg...
(Incremental) Priority algorithms
, 2003
"... We study the question of which optimization problems can be optimally or approximately solved by "greedylike " algorithms. For definiteness, we will limit the present discussion to some wellstudied scheduling problems although the underlying issues apply in a much more general ..."
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Cited by 40 (10 self)
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We study the question of which optimization problems can be optimally or approximately solved by &quot;greedylike &quot; algorithms. For definiteness, we will limit the present discussion to some wellstudied scheduling problems although the underlying issues apply in a much more general setting. Of course, the main benefit of greedy algorithms lies in both their conceptual simplicity and their computational efficiency. Based on the experience from online competitive analysis, it seems plausible that we should be able to derive approximation bounds for &quot;greedylike &quot; algorithms exploiting only the conceptual simplicity of these algorithms. To this end, we need (and will provide) a precise definition of what we mean by greedy and greedylike.
Approximation Algorithms for the Job Interval Selection Problem and Related Scheduling Problems
"... In this paper we consider the job interval selection problem (JISP), a simple scheduling model with a rich history and numerous applications. Special cases of this problem include the socalled realtime scheduling problem (also known as the throughput maximization problem) in single and multiple ma ..."
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Cited by 36 (3 self)
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In this paper we consider the job interval selection problem (JISP), a simple scheduling model with a rich history and numerous applications. Special cases of this problem include the socalled realtime scheduling problem (also known as the throughput maximization problem) in single and multiple machine environments. In these special cases we have to maximize the number of jobs scheduled between their release date and deadline (preemption is not allowed). Even the single machine case is NPhard. The unrelated machines case, as well as other special cases of JISP, are MAX SNPhard. A simple greedy algorithm gives a 2approximation for JISP. Despite many efforts, this was the best approximation guarantee known, even for throughput maximization on a single machine. In this paper, we break this barrier and show an approximation guarantee of less than 1.582 for arbitrary instances of JISP. For some special cases, we show better results.
TimeConstrained Scheduling of Weighted Packets on Trees and Meshes
 In Proceedings of 11th ACM Symposium on Parallel Algorithms and Architectures (SPAA
, 2003
"... The timeconstrained packet routing problem is to schedule a set of packets to be transmitted through a multinode network, where every packet has a source and a destination (as in traditional packet routing problems) as well as a release time and a deadline. The objective is to schedule the maximum ..."
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Cited by 20 (0 self)
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The timeconstrained packet routing problem is to schedule a set of packets to be transmitted through a multinode network, where every packet has a source and a destination (as in traditional packet routing problems) as well as a release time and a deadline. The objective is to schedule the maximum number of packets subject to deadline constraints. This problem is studied in [1], where it is shown that the problem is NPComplete even when the underlying topology is a linear array. Approximation algorithms are also provided in [1] for the linear array and the unidirectional ring for both the case where packets may be buffered in transit and the case where they may not be. In this paper we extend...
Timeoptimum packet scheduling for manytoone routing in wireless sensor net works
 in IEEE MASS
, 2006
"... This paper studies the WSN application scenario with periodical traffic from all sensors to a sink. We present a timeoptimum and energyefficient packet scheduling algorithm and its distributed implementation. We first give a general manytoone packet scheduling algorithm for wireless networks, a ..."
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Cited by 14 (3 self)
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This paper studies the WSN application scenario with periodical traffic from all sensors to a sink. We present a timeoptimum and energyefficient packet scheduling algorithm and its distributed implementation. We first give a general manytoone packet scheduling algorithm for wireless networks, and then prove that it is timeoptimum and costs max(2N(u1) − 1, N(u0) − 1) time slots, assuming each node reports one unit of data in each round. Here N(u0) is the total number of sensors, while N(u1) denotes the number of sensors in a sink’s largest branch subtree. With a few adjustments, we then show that our algorithm also achieves timeoptimum scheduling in heterogeneous scenarios, where each sensor reports a heterogeneous amount of data in each round. Then we give a distributed implementation to let each node calculate its dutycycle locally and maximize efficiency globally. In this packet scheduling algorithm, each node goes to sleep whenever it is not transceiving, so that the energy waste of idle listening is also mitigated. Finally, simulations are conducted to evaluate network performance using the Qualnet simulator. Among other contributions, our study also identifies the maximum reporting frequency that a deployed sensor network can handle.
Conversion of Coloring Algorithms into Maximum Weight Independent Set Algorithms
 Workshop on Approximation and Randomization Algorithms in Communication Networks (2000), Carleton Scienti
, 2000
"... A very general technique for converting approximation algorithms for the vertex coloring problem in a class of graphs into approximation algorithms for the maximum weight independent set problem (MWIS) in the same class of graphs is presented. The technique consists of solving an LPrelaxation o ..."
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Cited by 14 (5 self)
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A very general technique for converting approximation algorithms for the vertex coloring problem in a class of graphs into approximation algorithms for the maximum weight independent set problem (MWIS) in the same class of graphs is presented. The technique consists of solving an LPrelaxation of the MWIS problem with certain clique inequalities, constructing an instance of the vertex coloring problem from the LP solution, applying the coloring algorithm to this instance, and selecting the best resulting color class as the MWIS solution. The approximation ratio obtained is the product of the approximation ratio with which the LP formulation can be solved (usually equal to one) and the approximation ratio of the coloring algorithm with respect to the size of the largest relevant clique. Applying this technique, the best known approximation algorithms are obtained for the maximum weight edgedisjoint paths problem in bidirected trees and in bidirected twodimensional meshes ...
Packet pacing in short buffer optical packet switched networks
 in Proceedings of IEEE Infocom
, 2006
"... Abstract — In the absence of a costeffective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. This paper investigates the resulting impact on endtoend loss and throughput, and proposes that the opti ..."
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Cited by 11 (3 self)
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Abstract — In the absence of a costeffective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. This paper investigates the resulting impact on endtoend loss and throughput, and proposes that the optical edge switches “pace ” packets into the OPS core to improve performance without adversely affecting endtoend delays. In this context, our contributions are threefold. We first evaluate the impact of short buffers on the performance of realtime and TCP traffic. This helps us identify shorttimescale burstiness as the major contributor to performance degradation, so we propose that the optical edge switches pace the transmission of packets into the OPS core while respecting their delayconstraints. Our second contribution develops algorithms of polylogarithmic complexity that can perform optimal realtime pacing of high data rate traffic. Lastly, we show via simulations of a realistic network carrying realtime traffic that pacing can significantly reduce losses at the expense of a bounded increase in endtoend delay. The lossdelay tradeoff mechanism provided by pacing can help achieve desired OPS network performance. I.
WirelessHART TDMA protocol performance evaluation using response surface methodology
 in Broadband and Wireless Computing, Communication and Applications (BWCCA), 2011 International Conference on
, 2011
"... Abstract—Wireless HART is a stateoftheart solution for a timedivision multipleaccess (TDMA) based wireless privatearea network. It combines slow frequencyhopping and a TDMA scheme that utilizes a centralized apriori slot allocation mechanism. In this paper we conduct a performance evaluatio ..."
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Cited by 5 (0 self)
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Abstract—Wireless HART is a stateoftheart solution for a timedivision multipleaccess (TDMA) based wireless privatearea network. It combines slow frequencyhopping and a TDMA scheme that utilizes a centralized apriori slot allocation mechanism. In this paper we conduct a performance evaluation of the WirelessHART TDMA protocol and provide insights into the major factors impacting energy consumption. These insights provide valuable guidance on where to start with any effort geared towards saving energy. The main contributions of this paper are twofolds: (i) We conduct a sensitivity analysis of the WirelessHART TDMA energy consumption parameters using the response surface methodology. Based on these results we determine the most influential parameters for the total energy consumption. (ii) We evaluate and discuss the impact of time synchronization and types of link scheduling algorithms on the performance of WirelessHART TDMA protocol. I.
Universal Bufferless Routing
, 2004
"... In a routing problem, a set of packets must be routed from their sources to their destinations along specified paths in a connected network. The celebrated result of Leighton, Maggs and Rao (1988) established, nonconstructively, the existence of a routing schedule which uses constant size bffers an ..."
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Cited by 4 (2 self)
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In a routing problem, a set of packets must be routed from their sources to their destinations along specified paths in a connected network. The celebrated result of Leighton, Maggs and Rao (1988) established, nonconstructively, the existence of a routing schedule which uses constant size bffers and routes the packets in optimal time. Since then, constructive algorithms, as well as generalizations to distributed, buffered routing schedules have been developed. A long standing open problem...