Proportional Delay Differentiation Research Articles

Cascade self‐tuning control architecture for QoS‐aware MAC in WSN

Wireless sensor network (WSN) has proposed requirements more than just data collection and transmission. Different types of traffics call for different quality of service (QoS) demands. However, for the nature of uncertainty of wireless link and unpredictability of traffic transmission, it is very hard to distribute resources to different traffics precisely ahead of time. Based on the cascade self-tuning control, this study proposes the cascade self-tuning architecture for FD-MAC (CSFD-MAC) architecture. Taking the advantage of feedback theory, CSFD-MAC decouples contention window (CW) adaption and active time (AT) adaption into two separated cascading control loops. CW controller aims for the absolute node-to-node delay to a fixed value and AT controller guarantees the relative delay ratio. The software simulations illustrate the validity of controller design and the hardware experiments demonstrate the ability of CSFD-MAC in the absolute delay control as well as the proportional delay differentiation. More important, CSFD-MAC which takes AT as a controlled variable, not only has a much more superior performance in the metrics of delay and throughput compared with other QoS-aware MAC, but also has the advantage of efficient power management.

Cross-Layer Design for Proportional Delay Differentiation and Network Utility Maximization in Multi-Hop Wireless Networks

One major problem of cross-layer control algorithms in multi-hop wireless networks is that they lead to large end-to-end delays. Recently there have been many studies devoted to solving the problem to guarantee order-optimal per-flow delay. However, these approaches also bring the adverse effect of sacrificing a lot of network utility. In this paper, we solve the large-delay problem without sacrificing network utility. We take a fundamentally different approach of delay differentiation, which is based on the observation that flows in a network usually have different requirements for end-to-end delay. We propose a novel joint rate control, routing and scheduling algorithm called CLC_DD, which ensures that the flow delays are proportional to certain pre-specified delay priority parameters. By adjusting delay priority parameters, the end-to-end delays of preferential flows achieved by CLC_DD can be as small as those achieved by delay-order-optimal algorithms. In contrast to high network utility loss in previous approaches, we prove that our approach achieves maximum network utility. Furthermore, we incorporate opportunistic routing into the cross-layer design framework to improve network performance under the environment of dynamic wireless channels.

DIBS: A dual interval bandwidth scheduling algorithm for short-term differentiation

Packet delay and bandwidth are two important metrics for measuring quality of service (QoS) of Internet services. While proportional delay differentiation (PDD) has been studied intensively in the context of differentiated services, few studies were conducted for per-class short-term bandwidth differentiation. In this paper, we design and evaluate an efficient bandwidth differentiation algorithm. The dual interval bandwidth scheduling (DIBS) algorithm focuses on the short-term bandwidth differentiation of multiple classes because many Internet transactions take place in a small time frame. It does so based on the normalised instantaneous bandwidth, measured by the use of packet size and packet delay. It also uses two intervals to trade off differentiation accuracy and scheduling overhead. We implemented DIBS in the Click Modular Software Router. Extensive experiments have demonstrated the feasibility and effectiveness of DIBS in achieving short-term bandwidth differentiation. Compared with the representative PDD algorithm waiting time priority, DIBS can achieve better bandwidth differentiation when the inter-class packet size distributions are different. Compared with the representative weighted fair queueing algorithm per-packet generalized processor sharing, DIBS can achieve more accurate or comparable bandwidth differentiation at various workload situations, with better delay differentiation and lower cost. Furthermore, we apply DIBS to an adaptive intrusion detection and response system. Results demonstrate its efficiency for the rule-based rate-limiting function.

Model predictive control versus traditional proportional delay differentiation algorithms

An approximated quadratic programming optimization is proposed to determine a model predictive controller to guarantee end-to-end delay in the DiffServ architecture. The proposed algorithm, called the suboptimal model predictive control scheduler (SMPCS), regulates the service rates of aggregated traffic classes dynamically, such that some constraints on proportional or absolute delay can be guaranteed. This paper investigates SMPCS complexity and its implementation problems in high-speed routers. The main problem of model predictive control (and one which has limited its use to slow processes) is its complexity. Optimization is the most computationally complex part in a model predictive controller. To enable efficient implementation of such a computationally expensive algorithm, this paper proposes to reduce the precision of the optimizer while maintaining near-optimal values for the manipulated variables (service rates). Both control-theoretic analysis and simulations demonstrate that SMPCS performs stable and acceptable quality-of-service differentiations at core routers while maintaining end-to-end delay constraints.

Simultaneous and Proportional Bandwidth, Delay, and Loss Differentiation

A robust adaptive scheduler for proportional delay differentiation services is presented. Proportional services are further policed by a class-based packet dropper. Our proposed combination of the adaptive scheduler and the packet dropper treats the traffic classes proportionally in terms of three quality of service (QoS) metrics: bandwidth, delay, and packet loss, simultaneously. Traffic types used to study the performance of the scheme ranges from ordinary FTP data to bursty Pareto traffic. Numerical results validate our claim that regardless of the network traffic characteristics, especially burstiness, the adaptive delay scheduler combined with the packet dropper can effectively differentiate services in terms of delay, bandwidth, and loss simultaneously. In addition, our proposed scheme showed on an average 11% improvement in performance when compared to the scheme proposed in C. Dovrolis, D. Stiliadis, & P. Ramanathan, Proportional differentiated services: Delay differentiation and packet scheduling, IEEE/ACM Transactions on Networking, 10(1), 2002, 12–26.

An algorithm for achieving proportional delay differentiation

We consider the implementation of the proportional delay differentiation model with adaptive waiting time priority scheduler and we address the problem of finding the appropriate scheduler differentiation parameters that achieve this model. In this paper, we propose an algorithm that can compute an analytical solution of this problem.

Designing a Packet Scheduler for Proportional Delay Differentiation Model

We investigate the issues involved in designing a packet scheduler for the proportional delay differentiation (PDD) model in differentiated services (DiffServ) networks. The PDD model controls the average waiting time of each class such that the average waiting time is proportional to its corresponding delay differentiation parameter. This paper proposes a novel packet scheduler for PDD referred to as the longest waiting time first (LWTF). By adding certain conditions, we found that the LWTF scheduler can be reduced to a known packet scheduler-priority queue with linear priorities (PQ-LP). The properties and behaviors of LWTF can be predicted from the analysis of PQ-LP. The simulation results in comparison with other PDD algorithms have also revealed that LWTF provides no worse level of service quality in long timescales and affords more accurate and robust control over the delay ratio in short timescales.

Two schedulers to provide delay proportion and reduce queueing delay simultaneously

The proportional delay differentiation model provides controllable and predictable delay differentiation, that is, the packet delay proportion between two classes of services is consistent on any measured timescale. Previous studies have focused on improving the accuracy of the achieved delay proportion between classes, and have not considered reducing the packet queueing delay, since these proposed scheduling algorithms are independent of the packet service time, such that the mean queueing delay is invariant, as specified by the conservation law. This paper proposes maximum WTP (MWTP) and variance WTP (VWTP) schedulers, modified from the waiting-time priority (WTP) algorithm which is an excellent scheduler for performing proportional delay differentiation. All of the proposed schedulers account for the packet transmission time. Simulation results indicate that when the link utilization is moderate, the two schedulers not only yield more accurate delay proportions than the WTP scheduler, regardless of whether the timescale is long or short, but also reduce the mean queueing delay. The effects of load distribution, packet size, and coefficient of variation (CoV) of packet sizes, on the performance of all schedulers are also investigated. Our proposed schedulers always outperform WTP.

Provision of proportional delay differentiation in wireless LAN using a cross-layer fine-tuning scheduling scheme

The proportional delay differentiation (PDD) is one of the most well-known quality of service (QoS) models and has drawn much attention because of its ‘controllable’ and ‘predictable’ characteristics. How to provide PDD in a wireless LAN (WLAN) is addressed and a cross-layer fine-tuning scheduling (CFS) scheme with the goal to maintain PDD among all wireless stations is proposed, while improving performance in a WLAN. CFS additionally considers the time-varying channel capacity to schedule packets, finely tunes the contention window and properly arbitrates the backoff time. Also, it operates in a fully distributed manner among all stations and in a cross-layer approach in each station. The simulation results demonstrate that the CFS scheme can provide more satisfactory PDD and higher performance in a WLAN, compared with 802.11e.

Consistent proportional delay differentiation: A fuzzy control approach

Proportional delay differentiation (PDD) is an important service model for providing relative differentiated services on the Internet. It aims to maintain pre-specified packet queueing-delay ratios between different classes of traffic at each hop. Existing rate-allocation approaches for PDD services assume the average queueing delay of a class is inversely proportional to its service rate. This assumption is not necessarily valid when the system is not heavily loaded. To provide consistent PDD services under various load conditions, in this paper, we propose a novel rate-allocation approach that applies fuzzy control theory to capture the nonlinear relationship between the queueing delay and the service rate. In the approach, a class's service rate is adjusted according to a set of fuzzy control rules defined over its error (the difference between the target delay ratio and the achieved one), the change of error, and the change of service rate. We prove that the fuzzy control system is stable and the service rate of a class converges to its equilibrium point at steady state. Simulation results demonstrate that, in comparison with other rate-allocation approaches, the fuzzy control approach is able to provide consistent PDD services under wide range load conditions. It is also shown robust under various system conditions, including with multiple classes, changing target delay ratios, changing load conditions, and different traffic patterns.

A Non-Work-Conserving Scheduler to Provide Proportional Delay Differentiated Services and Best Effort Service

The proportional delay differentiation (PDD) model provides consistent packet delay differentiation between classes of service. Currently, the present schedulers performing the PDD model cannot achieve desired delay proportion observed in short timescales under light/moderate load. Thus, we propose a Non-Work-Conserving (NWC) scheduler, which utilizes the pseudo-waiting time for an empty queue and forces each class to compare its priority with those of all other classes. Simulation results reveal that NWC outperforms all current schedulers in achieving the PDD model. However, NWC suspends the server from transmitting packets immediately if an empty class has the maximum priority, resulting in an idle server. Therefore, we further propose two approaches, which will serve a best-effort class during this idle time. Compared with other schedulers, the proposed approaches can provide more predictable and controllable delay proportion, accompanied with satisfactory throughput and average queuing delay.

A robust packet scheduling algorithm for proportional delay differentiation services

Proportional delay differentiation (PDD) model is an important approach to relative differentiated services provisioning on the Internet. It aims to maintain pre-specified packet queueing-delay ratios between different classes of traffic at each hop. Existing PDD packet scheduling algorithms are able to achieve the goal in long time-scales when the system is highly utilized. This paper presents a new PDD scheduling algorithm, called Little’s average delay (LAD), based on a proof of Little’s Law. It monitors the arrival rate of the packets in each traffic class and the cumulative delays of the packets and schedules the packet according to their transient queueing properties in order to achieve the desired class delay ratios in both short and long time-scales. Simulation results show that LAD is able to provide predictable and controllable services in various system conditions and that such services, whenever feasible, can be guaranteed, independent of the distributions of packet arrivals and sizes. In comparison with other PDD scheduling algorithms, LAD can provide the same level of service quality in long time-scales and more accurate and robust control over the delay ratio in short time-scales. In particular, LAD outperforms its main competitors significantly when the desired delay ratio is large.

Admission control schemes for proportional differentiated services enabled internet servers using machine learning techniques

Abstract A widely existing problem in contemporary web servers is the unpredictability of response time. Owing to long response delay, revenues of the enterprises are substantially reduced due to many aborted e-commerce transactions. Recently, researchers have been addressing different admission control schemes of differentiated service for web servers to complement the Internet differentiated services model and thereby provide QoS support to the users of the World Wide Web. However, most of these admission control mechanisms do not guarantee the QoS requirements of all admitted clients under bursty workload. Although an Internet service model called proportional differentiated service is enabled in web servers to improve the QoS guarantee predicament in the literature, it still exists some impracticable assumptions and incompatible problems with the current Internet protocols. In this paper, we propose two algorithms for admission control and traffic scheduler schemes of the web server under proportional differentiated service, wherein a time series predictor is embedded to estimate the traffic load of the client in the next measurement time period. Support vector regression and particle swarm optimization techniques are used to implement the time series predictor based on the reports of successful prediction in the literature. The experimental results reveal that the proposed schemes can realize proportional delay differentiation service in multiclass Web server effectively. Meanwhile, the small computation overhead of particle swarm optimization verifies the feasibility of this machine learning technique in the real-time applications such as the admission control of the Internet server as illustrated in this work.

A Cross-Layer Approach for Concurrent Delay and Throughput Assurances in Multihop Wireless Hotspots

Next generation Wireless Local Area Networks (WLAN's) are likely to require multihop wireless connections between mobile nodes and Internet gateways to achieve high data rates from larger distances. The paper addresses the challenges in concurrently providing a wide range of end-to-end throughput and delay assurances in such mobile multihop WLAN hotspots. The proposed solution is based on the Neighborhood Proportional Delay Differentiation (NPDD) service model. With NPDD, Transmission Control Protocol (TCP) based applications achieve their desired throughputs using a dynamic class selection mechanism. This approach integrates well with the NPDD-based end-to-end delay assurance mechanism proposed earlier. To better model the node mobility in a multihop hotspot in our simulation studies, the Public Hotspot Mobility (PHM) model is proposed. Simulation results show that the proposed solution is better in meeting the desired throughputs and delays as compared with best effort and strict priority approaches. Recent theoretical analyses show that the NPDD model with a continuous range of classes can guarantee convergence to desirable QoS through dynamic class selection. However, the overhead of realizing the continuous class scheduler is high. We propose two continuous NPDD schedulers, the Single Queue Continuous NPDD (SQ-CNPDD) scheduler and the Multiple Queue Continuous NPDD (MQ-CNPDD) scheduler, to realize the continuous NPDD model. With simulations, the performance of SQ-CNPDD and MQ-CNPDD are compared to that of NPDD.

QoS assurances through class selection and proportional differentiation in wireless networks

Quality-of-service (QoS) in wireless ad hoc networks is adversely affected by node mobility, changing network topologies, and uncontrolled medium contention. The paper addresses the challenges in concurrently providing a wide range of end-to-end throughput and delay assurances in such networks. The proposed solution is based on the neighborhood proportional delay differentiation (NPDD) service model. With NPDD, applications achieve their desired end-to-end QoS using dynamic class selection (DCS) algorithms. With simulations in various distinct mobile network scenarios, we demonstrate the significantly better QoS assurances achieved with the proposed mechanism as compared with best effort and strict priority approaches. With game theoretic concepts, we model DCS applications in an NPDD network as selfish players in a noncooperative game. For such games, we prove for single-hop and multihop NPDD networks the existence of an equilibrium, the feasibility of an equilibrium, and the guaranteed convergence to a feasible equilibrium when one exists.

Achieving proportional delay differentiation in wireless LAN via cross‐layer scheduling

AbstractProviding service differentiation in wireless networks has attracted much attention in recent research. Existing studies so far have focused on the design of differentiated media access algorithms. Some quality of service (QoS) metrics, such as queueing delay cannot be completely addressed by these approaches. Moreover, without a formalized service differentiation goal that quantifies the outcome of differentiation, the performance of most of the approaches fluctuates, especially in short time‐scales.This paper addresses above problems by introducing the concept of proportional service differentiation, to the domain of wireless network and focuses on providing proportional delay differentiation in wireless LANs. Due to the unique characteristic of distributed medium sharing, the scheduling algorithm employed in wireline networks can not be applied directly to the context of wireless LANs. We argue that delay differentiation in wireless LAN can only be achieved through a joint packet scheduling at the network layer and distributed coordination at the media access control (MAC) layer. Therefore, we present a cross‐layer waiting time priority (CWTP) scheduling algorithm. CWTP consists of two tiers: an intra‐node waiting time priority (WTP) scheduler at the network layer and an inter‐node distributed coordination function at the MAC layer. These two tiers coordinate via a mapping function, which maps the normalized waiting time at the network layer to the backoff time at the MAC layer. Two mapping schemes, namely linear mapping and piecewise linear mapping, are presented and evaluated in this paper. Extensive simulation results show that the CWTP algorithm can effectively achieve proportional delay differentiation in wireless LANs. Copyright © 2004 John Wiley & Sons, Ltd.

Proportional delay differentiation provision by bandwidth adaptation of class‐based queue scheduling

AbstractSupporting quality of service (QoS) over the Internet is a very important issue and many mechanisms have already been devised or are under way towards achieving this goal. One of the most important approaches is the so‐called Differentiated Services (DiffServ) architecture, which provides a scalable mechanism for QoS support in a TCP/IP network. The main concept underlying DiffServ is the aggregation of traffic flows at an ingress (or egress) point of a network and the marking of the IP packets of each traffic flow according to several classification criteria. Diffserv is classified under two taxonomies: the absolute and the relative. In absolute DiffServ architecture, an admission control scheme is utilized to provide QoS as absolute bounds of specific QoS parameters. The relative DiffServ model offers also QoS guarantees per class but in reference to the guarantees given to the other classes defined. In this paper, relative proportional delay differentiation is achieved based on class‐based queueing (CBQ) scheduler. Specifically, the service rates allocated to the classes of a CBQ scheduler are frequently adjusted in order to obtain relative delay spacing among them. The model presented can also be exploited in order to meet absolute delay constraints in conjunction with relative delay differentiation provision. Simulation experiments verify that our model can attain relative as well as absolute delay differentiation provided that the preconditions posed are satisfied. Copyright © 2004 John Wiley & Sons, Ltd.

Scaled time priority: an efficient approximation to waiting time priority

Under the framework of DiffServ, Dovrolis presented the proportional differentiation model (PDM) [IEEE Network, October 1999] and found the waiting time priority (WTP) scheme [Proc. ACM SIGCOMM, September 1999] to be a suitable scheduling algorithm to achieve proportional delay differentiation. In this paper, we propose scaled time priority (STP), which is an efficient approximation to waiting time priority (WTP). In particular, STP is able to provide near proportional delay at a complexity of O(1), which is lower than WTP's O( N) complexity, where N is the number of service classes in the system. Simulation results show that STP is able to emulate the performance of WTP.

Achieving proportional delay differentiation efficiently

In this paper, we focus on efficiently achieving Proportional Delay Differentiation (PDD), an instance of the Proportional Differentiation Model first proposed under the DiffServ framework [IEEE Network (1999)]. PDD can be achieved using a few algorithms, one of the most well-known being Waiting Time Priority(WTP). Using WTP [Proc. ACM SIGCOMM (1999)] as a reference, we show that our proposed Scaled Time Priority (STP) algorithm is able to provide near proportional delay at a complexity of O(1), which is lower than the O( N) complexity of WTP, where N is the number of service classes in the system. Simulation results also show that STP is able to emulate the performance of WTP.

A novel scheduler for proportional delay differentiation by considering packet transmission time

The proportional delay differentiation model provides consistent packet delay differentiation between classes of service. The waiting time priority (WTP) scheduler is a priority scheduler in which the priority of a packet increases in proportion to its waiting time, and it is known as the best scheduler to achieve the proportional delay differentiation model. This paper proposes an advanced WTP (AWTP) scheduler, modified from WTP, that takes the packet transmission time into account. Simulation results reveal that when the link utilization is moderate (60%-90%), this scheduler not only obtains more accurate delay proportion than the WTP scheduler, but also reduces the average waiting time.