Providing Absolute Differentiated Services for Real-Time Applications in Static-Priority Scheduling Networks

In this paper, we propose and analyze a methodology for providing absolute differentiated services for real-time applications in networks that use static-priority schedulers. We extend previous work on worst-case delay analysis and develop a method that can be used to derive delay bounds without specific information on flow population. With this new method, we are able to successfully employ a utilization-based admission control approach for flow admission. This approach does not require explicit delay computation at admission time and hence is scalable to large systems. We assume the underlying network to use static-priority schedulers. We design and analyze several priority assignment algorithms, and investigate their ability to achieve higher utilization bounds. Traditionally, schedulers in differentiated services networks assign priorities on a classby -class basis, with the same priority for each class on each router. In this paper, we show that relaxing this requirement, that is, allowing different routers to assign different priorities to classes, achieves significantly higher utilization bounds

On Design and Realization of New Generation Misson-critial Application Systems

Mission-critical system typically refers to a project or system for which the success is vital to the mission of the underlying organization. The failure or delayed completion of the tasks in mission-critical systems may cause severe financial loss, even human casualties. For example, failure of an accurate and timely forecast of Hurricane Rita in September 2005 caused enormous financial loss and several deaths. As such, real-time guarantee and reliability have always been two key foci of mission-critical system design. Many factors affect real-time guarantee and reliability. From the software design perspective, which is the focus of this paper, three aspects are most important. The first of these is how to design a single application to effectively support real-time requirement and improve reliability, the second is how to integrate different applications in a cluster environment to guarantee real-time requirement and improve reliability, and the third is how to effectively coordinate distributed applications to support real-time requirements and improve reliability. Following these three aspects, this dissertation proposes and implements three novel methodologies: real-time component based single node application development, real-time workflow-based cluster application integration, and real-time distributed admission control. For ease of understanding, we introduce these three methodologies and implementations in three real-world mission-critical application systems: single node mission-critical system, cluster environment mission-critical system, and wide-area network mission-critical system. We study full-scale design and implementation of these mission-critical systems, more specifically: 1) For the single node system, we introduce a real-time component based application model, a novel design methodology, and based on the model and methodology, we implement a real-time component based Enterprise JavaBean (EJB) System. Through component based design, efficient resource management and scheduling, we show that our model and design methodology can effectively improve system reliability and guarantee real-time requirement. 2) For the system in a cluster environment, we introduce a new application model, a real-time workflow-based application integration methodology, and based on the model and methodology, we implement a data center management system for the Southeastern Universities Research Association (SURA) project. We show that our methodology can greatly simplify the design of such a system and make it easier to meet deadline requirements, while improving system reliability through the reuse of fully tested legacy models. 3) For the system in a wide area network, we narrow our focus to a representative VoIP system and introduce a general distributed real-time VoIP system model, a novel system design methodology, and an implementation. We show that with our new model and architectural design mechanism, we can provide effective real-time requirement for Voice over Internet Protocol (VoIP)

Utilization-based delay guarantee techniques and their applications

Many real-time systems demand effective and efficient delay-guaranteed services to meet timing requirements of their applications. We note that a system provides a delay-guaranteed service if the system can ensure that each task will meet its predefined end-to-end deadline. Admission control plays a critical role in providing delayguaranteed services. The major function of admission control is to determine admissibility of a new task. A new task will be admitted into the system if the deadline of all existing tasks and the new task can be met. Admission control has to be efficient and efficient, meaning that a decision should be made quickly while admitting the maximum number of tasks. In this dissertation, we study a utilization-based admission control mechanism. Utilization-based admission control makes an admission decision based on a simple resource utilization test: A task will be admitted if the resource utilization is lower than a pre-derived safe resource utilization bound. The challenge of obtaining a safe resource utilization bound is how to perform delay analysis offline, which is the main focus of this dissertation. For this, we develop utilization-based delay guarantee techniques to render utilization-based admission control both efficient and effective, which is further confirmed with our data. We develop techniques for several systems that are of practical importance. We first consider wired networks with the Differentiated Services model, which is wellknown as its supporting scalable services in computer networks. We consider both cases of providing deterministic and statistical delay-guaranteed services in wired networks with the Differentiated Services model. We will then extend our work to wireless networks, which have become popular for both civilian and mission critical applications. The variable service capacity of a wireless link presents more of a challenge in providing delay-guaranteed services in wireless networks. Finally, we study ways to provide delayguaranteed services in component-based systems, which now serve as an important platform for developing a new generation of computer software. We show that with our utilization-based delay guarantee technique, component-based systems can provide efficient and effective delay-guaranteed services while maintaining such advantages as the reusability of components

Intelligent adaptive bandwidth provisioning for quality of service in umts core networks

Master'sMASTER OF ENGINEERIN

Low-Latency Hard Real-Time Communication over Switched Ethernet

With the upsurge in the demand for high-bandwidth networked real-time applications in cost-sensitive environments, a key issue is to take advantage of developments of commodity components that offer a multiple of the throughput of classical real-time solutions. It was the starting hypothesis of this dissertation that with fine grained traffic shaping as the only means of node cooperation, it should be possible to achieve lower guaranteed delays and higher bandwidth utilization than with traditional approaches, even though Switched Ethernet does not support policing in the switches as other network architectures do. This thesis presents the application of traffic shaping to Switched Ethernet and validates the hypothesis. It shows, both theoretically and practically, how commodity Switched Ethernet technology can be used for low-latency hard real-time communication, and what operating-system support is needed for an efficient implementation

SUBMITTED TO IEEE/ACM TRANSACTIONS ON NETWORKING: IN REVISION 1 Providing Absolute Differentiated Services for Real-Time Applications in Static-Priority Scheduling Networks

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