Dynamic Traffic Scheduling and Resource Reservation Algorithms for Output-Buffered Switches

Scheduling algorithms implemented in Internet switches have been dominated by the best-effort and guaranteed service models. Each of these models encompasses the extreme ends of the correlation spectrum between service guarantees and resource utilisation. Recent advancements in adaptive applications have motivated active research in predictive service models and dynamic resource reservation algorithms. The OCcuPancy_Adjusting (OCP_A) is a scheduling algorithm focused on the design of the above-mentioned research areas. Previously, this algorithm has been analysed for a unified resource reservation and scheduling algorithm while implementing a tail discarding strategy. However, the differentiated services provided by the OCP _A algorithm can be further enhanced. In this dissertation, four new algorithms are proposed. Three are extensions of the OCP _A. The fourth algorithm is an enhanced version of the Virtual Clock (VC) algorithm, denoted as ACcelErated (ACE) scheduler. The first algorithm is a priority scheduling algorithm (i.e. known as the M-Tier algorithm) incorporated with a multitier dynamic resource reservation algorithm. Periodical resource reallocations are implemented. Thus. enabling each tier's resource utilisation to converge to its desired Quality of Service (QoS) operating point. In addition. the algorithm integrates a cross-sharing concept of unused resources between the various hierarchical levels to exemplify the respective QoS sensitivity. In the second algorithm. a control parameter is integrated into the M-Tier algorithm to ensure reduction of delay segregation effects towards packet loss sensitive traffic. The third algorithm, introduces a delay approximation algorithm to justify packet admission. The fourth algorithm enhances the VC scheduling algorithm. This is performed via the incorporation of dynamic features in the computation of the VC scheduling tag. Subsequently, the delay bound limitation of the parameter is eliminated

Predictive Quality Of Service Schemes For Real-Time Multimedia Applications In Communications

In guaranteed QoS resources are reserved based on the worst-case analysis. This scheme guarantees QoS but results in low resource utilisation, subsequently depriving other users from acquiring service. In contrary, predictive QoS allocates an initial amount of resource, whereby QoS is guaranteed with a certain probability of degradation. This scheme is tailored for applications that are adaptive and robust towards sudden fluctuations in the service provided. The nature of multimedia data such as the variable bit rate has encouraged the implementation of predictive Quality of Service (QoS) as compared to guaranteed QoS. In a typical QoS scheme, two factors contribute to the computation of packet loss, which are : (i) a new packet dropped due to buffer overflow and (ii) a buffered packet dropped due to expired delay. The buffer resource is increased when the observed packet loss ratio has violated the requested level of packet loss ratio. The limitations in this scheme is caused by the admission of all packets into the buffer, inclusive of packets that will eventually be dropped due to expired delay. Subsequently, this results in poor resource management. In this research, two pro-active dynamic QoS control schemes are designed, the dynamic QoS control scheme with delay estimation, and the hybrid dynamic QoS control scheme. In both schemes, every new packet arrival is compared against the estimated delay it will experience, before being admitted into the buffer. If the estimated delay expires the requested delay bound, then the packet is dropped. In the hybrid scheme, every packet is checked before being admitted into the buffer, and also, the packets successfully admitted into the buffer are evaluated on the actual delay experienced before being transmitted to the receIver. The results obtained through the simulation models have shown that two schemes have significantly improved the average delay for different traffic patterns. In addition to improving the average delay in delay sensitive traffic, improvement is seen in the average packet loss ratio, and subsequently increasing the throughput for delay sensitive traffic. However, in packet loss sensitive traffic, the old scheme remains beneficial. The proposed scheme can be adopted for multimedia applications to enhance the QoS in terms of better delay and improved utilisation

Modeling and simulation: the paradigm shift for cohesive resource harnessing

This paper presents the details of a specialized framework developed for the teaching of the modeling and simulation course for postgraduate students in Universiti Putra Malaysia. The unique feature of the subject is that it requires students ability to gain knowledge in several fields and relate them aptly to the need of performance analysis. IT also demands acquiring skills to develop comprehensive tools using the principles of discrete event simulation. The developed framework focuses on student-centered learning of queuing analysis, the development of models and relating them to performance analysis, the specialized activities to derive discrete event simulation components, and output analysis. It also deals with the tool's impact on research within the area. The framework was evaluated in a course. It showed the ability to enhance the level of student's understanding and application of competency gained to research

Cohesive token passing algorithm utilizing software agents

The communications domain has utilized the implementation of protocols for a wide spectrum of applications. This encompasses Medium Access Control (MAC) protocols. MAC protocols have been extensively researched from several angles. This encompasses the implementation in the area of Wave Division Multiplexing (WDM) networks and Mobile Adhoc Networks (MANET). The relevance of intelligence in sustaining the pre-requisites for dynamic reconfiguration has gained an integral attention in MANET. Approach: The implementation of Token Ring in MANET can be correlated to its complementary implementation in IP networks. In this paper, the limitation of Token Ring algorithm for IP networks in the context of intelligent processing has been researched extensively. An enhanced Token Ring protocol governed by intelligent processing has been implemented in this paper. The core of the new protocol is based on the circulation mechanism of the token. As opposed to the traditional circulatory mechanism, a software agent is designed to become an intelligent circulatory agent is this research. The developed software agent is utilized to implement prioritized token access subject to the traffic type. Each station is coupled with a software agent who cohesively collaborates to assign the token. Results: The proposed agent and the enhanced Token Ring implementation have been extensively verified through simulation experiments. A complete circulation of the ring is defined upon all nodes being visited at least once. Discrete-event simulation models were developed and deployed for the purpose of performance analysis. The results acquired validated the improved results of the new software agent based implementation. The performance metrics studied were average delay and average buffer utilization. Conclusion: The proposed algorithm has enabled to derive an ideal balance between the complexity of intelligent processing and the versatility of managing the token ring

Evaluation Study for Delay and Link Utilization with the New-Additive Increase Multiplicative Decrease Congestion Avoidance and Control Algorithm

As the Internet becomes increasingly heterogeneous, the issue of congestion avoidance and control becomes ever more important. And the queue length, end-to-end delays and link utilization is some of the important things in term of congestion avoidance and control mechanisms. In this work we continue to study the performances of the New-AIMD (Additive Increase Multiplicative Decrease) mechanism as one of the core protocols for TCP congestion avoidance and control algorithm, we want to evaluate the effect of using the AIMD algorithm after developing it to find a new approach, as we called it the New-AIMD algorithm to measure the Queue length, delay and bottleneck link utilization, and use the NCTUns simulator to get the results after make the modification for the mechanism. And we will use the Droptail mechanism as the active queue management mechanism (AQM) in the bottleneck router. After implementation of our new approach with different number of flows, we expect the delay will less when we measure the delay dependent on the throughput for all the system, and also we expect to get end-to-end delay less. And we will measure the second type of delay a (queuing delay), as we shown in the figure 1 bellow. Also we will measure the bottleneck link utilization, and we expect to get high utilization for bottleneck link with using this mechanism, and avoid the collisions in the link

Dynamic layout algorithms for wireless field hockey strategy system

Sensor deployment in the field of sports is providing enormous potential for elevating the playing field standards. This paper presents an enhanced localization algorithm which harnesses the dynamic and reconfiguration attributes of field hockey players on a strategy board; known as the Wireless Field Hockey Strategy System (WiHoc Ver1.0). The proposed algorithm utilized for determining the location of field hockey players overcomes the constraints and confined anchor based WiHoc Ver 1.0. The resolution encompasses the new versatile platform which captures the positional location within the parameters of a hockey pitch and of cooperative nodes to determine the optimal location of anchor positioning to ensure that the achieved accuracy of localization is enhanced. The proposed algorithm was evaluated extensively through discrete - event simulations. The acquired results via the accuracy performance metrics validated the enhanced ability of the proposed algorithm

An event-driven simulation for highest urgency first (HUF) : a latency and modulation aware bandwidth allocation algorithm for WiMAX base stations.

Awide-spectrum of WiMAX simulators have been developed to provide analysis for advanced WiMAX system development, including the open source tool ns-2, and commercial software such as QualNet and OPNET Modeler. These tools are among the pertinent simulators,however,there are trade-offs such as complexity,large integrated components and licensing cost for commercial simulators. To strike an ideal balance in gauging these trade-offs and to further complement the repository of simulators, this paper presents the details of a general-purpose programming language based discrete event simulation for WiMAX. This research has focused at developing a discrete-event simulator to implement bandwidth allocation algorithms for a WiMAX base station.The highest urgency first algorithm has been utilized as a benchmark deployment algorithm in order to provide: dynamic downlink/uplink adjustment and latency guarantee for real-time applications. Two performance analyses have been deployed for the purpose of extensive testing of the developed simulator. The analysis encompasses the modulation and coding scheme awareness and the latency guarantee with multiple and distinct requirements. The results show that the developed simulator has successfully produced the benchmark results. These findings have proved that the new simulator has successfully become a reliable option for WiMAX resource management performance analysis

New algorithms to minimize handoff latency in AMTree protocol

In active networks, programs can be injected to network elements (routers/switches). This allows programmers to enhance existing protocols or deploy new protocols. AMTree protocol is an active network based protocol that makes sending packets to receivers, after source migration, an efficient process. In AMTree protocol, after source migration, handoff latency computed from the time of reconnecting to a new base station until finding nearest core to the mobile source. In this paper the authors present two new algorithms to minimize the handoff latency in AMTree protocol. They show that handoff latency is much lower than that of AMTree handoff algorithm if the mobile source connects to a base station which is subscribed to the multicast group

Optimal workload allocation model for scheduling divisible data grid applications

In many data grid applications, data can be decomposed into multiple independent sub-datasets and distributed for parallel execution and analysis. This property has been successfully employed using Divisible Load Theory (DLT), which has been proved a powerful tool for modeling divisible load problems in data-intensive grids. There are some scheduling models that have been studied but no optimal solution has been reached due to the heterogeneity of the grids. This paper proposes a new model called the Iterative DLT (IDLT) for scheduling divisible data grid applications. Recursive numerical closed form solutions are derived to find the optimal workload assigned to the processing nodes. Experimental results show that the proposed IDLT model leads to a better solution than other models (almost optimal) in terms of makespan

Load allocation model for scheduling divisible data grid applications.

Problem statement: In many data grid applications, data can be decomposed into multiple independent sub-datasets and distributed for parallel execution and analysis. Approach: This property had been successfully employed by using Divisible Load Theory (DLT), which had been proved as a powerful tool for modeling divisible load problems in data-intensive grid. Results: There were some scheduling models had been studied but no optimal solution has been reached due to the heterogeneity of the grids. This study proposed a new optimal load allocation based on DLT model recursive numerical closed form solutions are derived to find the optimal workload assigned to the processing nodes. Conclusion/Recommendations: Experimental results showed that the proposed model obtained better solution than other models (almost optimal) in terms of Makespan