Traffic Burstiness Research Articles

Cooperative Access in Wireless Networks: Stable Throughput and Delay

We investigate the impact of a protocol-level cooperation idea in a wireless multiple-access system. By dynamically and opportunistically exploiting spatial diversity among the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$N$</tex></formula> source users, a packet is delivered to the common destination through either a direct link or through cooperative relaying by intermediate source nodes that have a statistically better channel to the destination. The traffic burstiness at the source is taken into account, and the performance metrics of the stable throughput region and delay are evaluated for the case of packet-erasure channels. We consider conflict-free, work-conserving transmission policies as well as plain time-division multiple-access policy. We establish that the stable throughput regions under both classes of cooperative policies are the same, which strictly contain the stable throughput regions achieved without cooperation. Moreover, the optimal policy for minimizing the average delay among the class of all cooperative work-conserving policies is determined. Then, in the case of two users, the closed-form delay expressions are explicitly derived as well. Our results indicate that cooperation can significantly reduce delay for both users.

Analysis of the MAC protocol in low rate wireless personal area networks with bursty ON–OFF traffic

SUMMARYSupported by the IEEE 802.15.4 standard, embedded sensor networks have become popular and been widely deployed in recent years. The IEEE 802.15.4 medium access control (MAC) protocol is uniquely designed to meet the desirable requirements of the low end‐to‐end delay, low packet loss, and low power consumption in the low rate wireless personal areas networks (LR‐WPANs). This paper develops an analytical model to quantify the key performance metrics of the MAC protocol in LR‐WPANs with bursty ON–OFF traffic. This study fills the gap in the literature by removing the assumptions of saturated traffic or nonbursty unsaturated traffic conditions, which are unable to capture the characteristics of bursty multimedia traffic in sensor networks. This analytical model can be used to derive the QoS performance metrics in terms of throughput and total delay. The accuracy of the model is verified through NS‐2 (http://www.isi.edu/nsnam/ns/) simulation experiments. This model is adopted to investigate the performance of the MAC protocol in LR‐WPANs under various traffic patterns, different loads, and various numbers of stations. Numerical results show that the traffic patterns and traffic burstiness have a significant impact on the delay performance of LR‐WPANs. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Modeling and Analysis of Communication Networks in Multicluster Systems under Spatio-Temporal Bursty Traffic

Multicluster systems have emerged as a promising infrastructure for provisioning of cost-effective high-performance computing and communications. Analytical models of communication networks in cluster systems have been widely reported. However, for tractability and simplicity, the existing models are based on the assumptions that the network traffic follows the nonbursty Poisson arrival process and the message destinations are uniformly distributed. Recent measurement studies have shown that the traffic generated by real-world applications reveals the bursty nature in both the spatial domain (i.e., nonuniform distribution of message destinations) and temporal domain (i.e., bursty message arrival process). In order to obtain a comprehensive understanding of the system performance, a novel analytical model is developed for communication networks in multicluster systems in the presence of the spatio-temporal bursty traffic. The spatial traffic burstiness is captured by the communication locality and the temporal traffic burstiness is modeled by the Markov-modulated Poisson process. After validating its accuracy through extensive simulation experiments, the model is used to investigate the impact of bursty message arrivals and communication locality on network performance. The analytical results demonstrate that the communication locality can relieve the degrading effects of bursty message arrivals on the network performance.

Internet Traffic Classification Using the Index of Variability

Internet Traffic Classification aims at the identification of the Internet application that generates a given sequence of packets. Shallow Packet Inspection (SPI) is a new family of classification techniques that only use information available in the external header of packets and the statistical characterization of the traffic process. Therefore, these techniques are applicable even to encrypted or obfuscated traffic. The packet arrival process is a particularly interesting features for traffic classification, as it is difficult to significantly modify it. This paper proposes a classification technique based on a classification feature called Index of Variability, which evaluates the traffic source burstiness over various time scales in order to discriminate among different classes of Internet applications. Experimental results show that this classification method operates effectively both on synthetic and real traffic traces. Synthetic traffic traces make it possible to estimate the classification error rate achieved by the classification algorithm. The usage of real traces allows us to compare the performance of the method to the performance obtained with Deep Packet Inspection (DPI) techniques, showing that SPI and DPI yields similar results.

An integrated buffer management strategy for the TDD mode in IEEE 802.16 BWA networks

Considering IEEE 802.16 networks having different types of service flows, in this paper, we propose a rearranging scheme of a two-tier hierarchy for the TDD mode in IEEE 802.16 broadband wireless access networks to dynamically adapt to the traffic burstiness according to the change of instant buffers on buffer management. We demonstrate the performance improvement of the rearranging scheme in terms of accumulated throughput and fairness in the finite buffer case compared with the fixed rule by simulations. The simulation results show that the proposed scheme in the case of finite buffer depth not only can provide much better fairness and achieve higher accumulated throughput but also is less buffer-consuming than that without rearranging, meaning that the hardware cost can be reduced by employing the proposed scheme.

Design of Active Queue Management for Robust Control on Access Router for Heterogeneous Networks

The Internet architecture is a packet switching technology that allows dynamic sharing of bandwidth among different flows with in an IP network. Packets are stored and forwarded from one node to the next until reaching their destination. Major issues in this integration are congestion control and how to meet different quality of service requirements associated with various services. In other words streaming media quality degrades with increased packet delay and jitter caused by network congestion. To mitigate the impact of network congestion, various techniques have been used to improve multimedia quality and one of those techniques is Active Queue Management (AQM). Access routers require a buffer to hold packets during times of congestion. A large buffer can absorb the bursty arrivals, and this tends to increase the link utilizations but results in higher queuing delays. Traffic burstiness has a considerable negative impact on network performance. AQM is now considered an effective congestion control mechanism for enhancing transport protocol performance over wireless links. In order to have good link utilization, it is necessary for queues to adapt to varying traffic loads. This paper considers a particular scheme which is called Adaptive AQM (AAQM) and studies its performance in the presence of feedback delays and its ability to maintain a small queue length as well as its robustness in the presence of traffic burstiness. The paper also presents a method based on the well-known Markov Modulated Poisson Process (MPP) to capture traffic burstiness and buffer occupancy. To demonstrate the generality of the presented method, an analytic model is described and verified by extensive simulations of different adaptive AQM algorithms. The analysis and simulations show that AAQM outperforms the other AQMs with respect to responsiveness and robustness.

Joint MAC and rate control for stability and delay in wireless multi-access channels

In this paper, we investigate the stability and delay issues of a two-user multi-access channel at the bit level. The two users, have the option to transmit at a higher instantaneous rate separately, or to transmit simultaneously but at a lower individual instantaneous rate due to interference caused by concurrent transmissions. Traffic burstiness is considered by modeling random arrivals at the users, and the stability region in terms of bits/slot is derived. Further, we determine the condition under which the maximum stability region is achieved when the users always transmit if their queues are non-empty; in this case, the stability region is shown to be convex. Subsequently, we study the minimum delivery time problem where each user is allocated an initial amount of traffic volume to be sent to the destination. For any initial queue size vector, we explicitly characterize the optimal policy that empties the two users’ queues within the shortest time.

Performance of Random Contention PRMA: A Protocol for Fixed Wireless Access

This paper introduces a packet reservation multiple access (PRMA) with random contention for fixed wireless access communications. The performance of PRMA scheme with random contention is compared with the performances of traditional PRMA under permission contention scheme. The proposed scheme is a simpler contention mechanism that does not depend on a pre-determined permission probability as PRMA under permission contention scheme. In this new method, terminals select the contention slot uniformly from the pool of remaining free slots in the current frame. We evaluate the performance of the new contention mechanism in terms of various metrics including maximum number of carried voice calls and packet delays for a given acceptable drop rate of voice packets. We show that the new mechanism is superior to that of PRMA under permission contention scheme for loaded systems and is expected to be insensitive for traffic source burstiness.

Analysis of traffic correlation attacks on router queues

Traffic burstiness is known to be undesirable for a router as it increases the router’s queue length and hence the queueing delays of data flows. This poses a security problem in which an attacker intentionally introduces traffic burstiness into routers. We consider a correlation attack, whose fundamental characteristic is to correlate multiple attack flows to generate synchronized small attack bursts, in an attempt to aggregate the bursts into a large burst at a target router.In this paper, we develop an analytical, fluid-based framework that models how the correlation attack disrupts router queues and how it can be mitigated. Using Poisson Counter Stochastic Differential Equations (PCSDEs), our framework captures the dynamics of a router queue for special cases and gives the closed-form average router queue length as a function of the inter-flow correlation. To mitigate the correlation attack, we apply our analytical framework to model different pacing schemes including Markov ON–OFF pacing and rate limiting, which are respectively designed to break down the inter-flow correlation and suppress the peak rates of bursts. We verify that our fluid models conform to packet-level ns2 simulation results.

Performance analysis of an integrated scheduling scheme in the presence of bursty MMPP traffic

Contemporary communication networks are expected to support multimedia applications which require diversified Quality-of-Services (QoS). An integrated scheduling discipline of Priority Queueing (PQ) and Generalized Processor Sharing (GPS), referred to as P–G, has recently emerged as a promising scheme for cost-effective QoS differentiation. In this paper, we develop a new analytical model for the integrated P–G system subject to bursty traffic. The Markov-Modulated Poisson Process (MMPP) is adopted to capture traffic burstiness because it can qualitatively model time-varying arrival rate and important correlation between inter-arrival times. To derive the desired performance metrics for individual sessions, the integrated P–G system is decomposed into a set of Single-Server Single-Queue (SSSQ) systems. Specifically, the integrated system is first divided into an SSSQ system and a GPS system. Next, a bounding approach is adopted to decompose the GPS system into individual SSSQ systems. Extensive comparisons between analytical and simulation results validate the accuracy of the analytical model. To demonstrate its merits, the model is used to investigate the configuration of the GPS weights under the QoS constraints of different traffic flows.

Analytical modeling of an integrated priority and WFQ scheduling scheme in multi-service networks

The provisioning of differentiated Quality-of-Service (QoS) is a key objective in the design and deployment of convergent multi-service communication networks. Integrated traffic management schemes that combine various fundamental scheduling principles have been proposed for the QoS differentiation in cellular and IEEE 802.16/WiMAX-based broadband wireless networks. In this paper, cost-effective analytical performance models are devised for a new hybrid scheduling scheme based on the integration of the well-known Priority Queueing (PQ) and Weighted Fair Queueing (WFQ) scheduling principles. In these models, traffic arrival processes are represented, respectively, by non-bursty Poisson process and bursty-correlated Markov-Modulate Poisson Process (MMPP) and new closed-form expressions of main performance metrics are derived including system fairness, mean number of packets in each buffer, system throughput, mean queueing delay and packet loss probability of individual traffic flows. The accuracy of the analytical models is validated through extensive comparisons between analytical results and those obtained from simulation experiments. Finally, these models are adopted to investigate the impact of the weights of traffic flows served by WFQ and assess the adverse effects of the traffic burstiness and correlation on the performance of the integrated scheduling scheme.

Dynamic OBS offset allocation in WDM networks

An investigation is carried out into the traffic characteristics of an OC-192 link (9953 Mbps), based on the IP packet size distribution, traffic burstiness and self-similarity. The Generalised Exponential (GE) distribution is employed as a suitable model of interarrival times of bursty traffic flows of IP packets whilst self-similar traffic is generated for each wavelength of each source node in the optical network. In this context, a novel optical burst switching (OBS) allocation protocol is proposed, based on the offset values of adapting source–destination pairs, using preferred wavelengths specific to each destination node. Different traffic demands amongst the nodes of the optical network are taken into account and a dynamic updating of the offset is adopted based on the occurrence of blocked bursts and successful transmissions. Numerical evaluation results based on simulation are devised and favourable comparisons are carried out between the proposed OBS protocol and the Just Enough Time (JET) protocol, based on the performance metrics of mean queue length, blocking and throughput.

Describing Network Traffic Using the Index of Variability

Commonly used measures of traffic burstiness do not capture the fluctuation of traffic variability over the entire range of time-scales. In this paper, we present a measure of variability, called the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Index of Variability</i> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hv</i> (tau)), that depicts the degree of variability (burstiness) of a typical network traffic process at each time-scale and is analytically tractable for many traffic models. As an illustration, we derive the closed-form expressions of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hv</i> (tau) for two traditional traffic models and generate a variety of two-dimensional (2D) and three-dimensional (3D) Index-of-Variability curves. These curves demonstrate that the Index of Variability can help in determining the complexities of the network traffic variability over the network performance relevant time-scales. We then introduce a practical method for estimating the Index-of-Variability curve from a given traffic trace. Using this method, we estimate the Index-of-Variability curves for 12 long NLANR network traffic traces. The results indicate that the variability of real network traffic varies with time-scales and that the Index of Variability has the ability to discern qualitative differences between traffic traces obtained from different networks. Thus, the Index of Variability offers the potential to gain insights into the dynamics of network traffic that existing tools do not offer.

Packet Pacing in Small Buffer Optical Packet Switched Networks

In the absence of a cost-effective technology for storing optical signals, emerging optical packet switched (OPS) networks are expected to have severely limited buffering capability. To mitigate the performance degradation resulting from small buffers, this paper proposes that optical edge nodes ldquopacerdquo the injection of traffic into the OPS core. Our contributions relating to pacing in OPS networks are three-fold: first, we develop real-time pacing algorithms of poly-logarithmic complexity that are feasible for practical implementation in emerging high-speed OPS networks. Second, we provide an analytical quantification of the benefits of pacing in reducing traffic burstiness and traffic loss at a link with very small buffers. Third, we show via simulations of realistic network topologies that pacing can significantly reduce network losses at the expense of a small and bounded increase in end-to-end delay for real-time traffic flows. We argue that the loss-delay tradeoff mechanism provided by pacing can be instrumental in overcoming the performance hurdle arising from the scarcity of buffers in OPS networks.

Practical High-Throughput Crossbar Scheduling

A practical deterministic crossbar scheduler achieves almost full throughput without being heavily affected by short virtual output queues or traffic burstiness. Simple additions offer deterministic service guarantees and distribute the bandwidth of congested links in a weighted, fair manner. Input-queued crossbars are the common building blocks in Internet routers, data center and high-performance computing interconnects, and on-chip networks. These crossbars often contain no buffers, which saves valuable chip area. Arriving packets issue requests to a central scheduler. While waiting for the scheduler to grant their requests, packets wait at input packet buffers in front of the crossbar. To isolate traffic for different outputs, these input buffers are often organized as virtual output queues (VOQs).

Identifying MMORPG Bots: A Traffic Analysis Approach

Massively multiplayer online role playing games (MMORPGs) have become extremely popular among network gamers. Despite their success, one of MMORPG's greatest challenges is the increasing use of game bots, that is, autoplaying game clients. The use of game bots is considered unsportsmanlike and is therefore forbidden. To keep games in order, game police, played by actual human players, often patrol game zones and question suspicious players. This practice, however, is labor-intensive and ineffective. To address this problem, we analyze the traffic generated by human players versus game bots and propose general solutions to identify game bots. Taking Ragnarok Online as our subject, we study the traffic generated by human players and game bots. We find that their traffic is distinguishable by 1) the regularity in the release time of client commands, 2) the trend and magnitude of traffic burstiness in multiple time scales, and 3) the sensitivity to different network conditions. Based on these findings, we propose four strategies and two ensemble schemes to identify bots. Finally, we discuss the robustness of the proposed methods against countermeasures of bot developers, and consider a number of possible ways to manage the increasingly serious bot problem.

Service Adoption and Pricing of Content Delivery Network (CDN) Services

Content delivery networks (CDNs) are a vital component of the Internet's content delivery value chain, servicing nearly a third of the Internet's most popular content sites. However, in spite of their strategic importance, little is known about the optimal pricing policies or adoption drivers of CDNs. We address these questions using analytic models of CDN pricing and adoption under Markovian traffic and extend the results to bursty traffic using numerical simulations. When traffic is Markovian, we find that CDNs should provide volume discounts to content providers. In addition, the optimal pricing policy entails lower emphasis on value-based pricing and greater emphasis on cost-based pricing as the relative density of content providers with high outsourcing costs increases. However, when traffic is bursty and content providers have varying levels of traffic burstiness, volume discounts may be suboptimal and may even be replaced by volume taxes. Finally, when there is heterogeneity in burstiness across content providers, a pricing policy that accounts for both the mean and variance in traffic such as percentile-based pricing is more profitable than traditional volume-based pricing (metering bytes delivered in a given time window). This finding is in contrast to the current practices of many CDN firms that use traditional volume-based pricing.

Towards an end-to-end delay analysis of wireless multihop networks

In wireless multihop networks, end-to-end (e2e) delay is a critical parameter for quality of service (QoS) guarantees. We employ discrete-time queueing theory to analyze the end-to-end (e2e) delay of wireless multihop networks for two MAC schemes, m-phase TDMA and slotted ALOHA. In one-dimensional (1-D) networks, due to the lack of sufficient multiplexing and splitting, a space–time correlation structure exists, the nodes are spatially correlated with each other, and the e2e performance cannot be analyzed as in general two-dimensional networks by assuming all nodes independent of each other. This paper studies an 1-D network fed with a single flow, an extreme scenario in which there is no multiplexing and splitting. A decomposition approach is used to decouple the whole network into isolated nodes. Each node is modeled as a GI/Geo/1 queueing system. First, we derive the complete per-node delay distribution and departure characterization, accounting for both the queueing delay and access delay. Second, based on the departure process approximation, we define a parameter to measure the spatial correlation and its influence on the e2e delay variance. Our study shows that traffic burstiness of the source flow and MAC together determines the sign of the correlation.

Design of the Cross-Layer QoS Framework for the IEEE 802.16 PMP Networks

As one of the promising techniques in Broadband Wireless Access (BWA), IEEE 802.16 also namely WiMax provides wide-area, high-speed, and non-line-of-sight wireless transmission to support multimedia services. Four service types are defined in the specification of IEEE 802.16 for QoS support. In order to achieve end-to-end multimedia services, 802.16 QoS must be well integrated with IP QoS. In this paper, we propose a framework of cross-layer QoS support in the IEEE 802.16 network. Two novel mechanisms are proposed in the framework for performance improvement: Fragment Control and Remapping. Fragment Control handles the data frames that belong to the same IP datagram in an atomic manner to reduce useless transmission. Remapping is concerned with the mapping rules from IP QoS to 802.16 QoS and is designed to reduce the impact of traffic burstiness on buffer management. Simulation study has shown that the proposed scheme has higher goodput and throughput, and lower delay than the contrast.

STOCHASTIC MODELING AND ANALYSIS OF AN ACTIVE CONGESTION CONTROL PROTOCOL UNDER DIFFERENTIATED BURSTY TRAFFIC

Traffic congestion degrades not only the user-perceived Quality-of-Service (QoS), such as leading to high packet loss rates, low throughput, and increased delays, but also causes excessive energy consumption in energy-sensitive systems (e.g., wireless sensor networks). A simple way to detect congestion is to monitor and measure queue length in network nodes or routers. This paper develops an analytical performance model for a finite capacity queueing system with an enhanced Random Early Detection (RED) congestion control scheme based on the instantaneous queue length in the presence of differentiated classes of bursty traffic. The aggregate traffic is captured by the superposition of 2-state Markov Modulated Poisson Processes (MMPP). The individual threshold is assigned to each traffic class in order to differentially control traffic injection rate. The accuracy of this model is verified by comparing the analytical results against those obtained from simulation experiments. The model is adopted to investigate the effects of traffic burstiness and system capacity on the performance of the congestion control scheme.