Middleware for transparent TCP connection migration : masking faulty TCP-based services

Masteroppgave i informasjons- og kommunikasjonsteknologi 2004 - Høgskolen i Agder, GrimstadMission critical TCP-based services create a demand for robust and fault tolerant TCP communication. Sense Intellifield monitors drill operations on rig sites offshore. Critical TCP-based services need to be available 24 hours, 7 days a week, and the service providers need to tolerate server failure. How to make TCP robust and fault tolerant without modifying existing infrastructure like existing client/server applications, services, TCP stacks, kernels, or operating systems is the motivation of this thesis. We present a new middleware approach, first of its kind, to allow TCP-based services to survive server failure by migrating TCP connections from failed servers to replicated surviving servers. The approach is based on a proxy technique, which requires modifications to existing infrastructure. Our unique middleware approach is simple, practical, and can be built into existing infrastructure without modifying it. A middleware approach has never been used to implement the proxy based technique. Experiments for validation of functionality and measurement of performance of the middleware prototype are conducted. The results show that our technique adds significant robustness and fault tolerance to TCP, without modifying existing infrastructure. One of the consequences of using a middleware to make TCP communication robust and fault tolerant is added latency. Another consequence is that TCP communication can survive server failure, and mask it. Companies providing robust and fault tolerant TCP, is no longer dependant of third party hardware and/or software. By implementing our solution, they can gain economical advantages. A main focus of this report is to present a prototype that demonstrates our technique and middleware approach. We present relevant background theory which has lead to the design architecture of a middleware approach to make TCP communication fault tolerant. Finally we conduct experiments to uncover the feasibility and performance of the prototype, followed by a discussion and conclusion

Ubiquitous Computing for Remote Cardiac Patient Monitoring: A Survey

New wireless technologies, such as wireless LAN and sensor networks, for telecardiology purposes give new possibilities for monitoring vital parameters with wearable biomedical sensors, and give patients the freedom to be mobile and still be under continuous monitoring and thereby better quality of patient care. This paper will detail the architecture and quality-of-service (QoS) characteristics in integrated wireless telecardiology platforms. It will also discuss the current promising hardware/software platforms for wireless cardiac monitoring. The design methodology and challenges are provided for realistic implementation

An adaptive admission control and load balancing algorithm for a QoS-aware Web system

The main objective of this thesis focuses on the design of an adaptive algorithm for admission control and content-aware load balancing for Web traffic. In order to set the context of this work, several reviews are included to introduce the reader in the background concepts of Web load balancing, admission control and the Internet traffic characteristics that may affect the good performance of a Web site. The admission control and load balancing algorithm described in this thesis manages the distribution of traffic to a Web cluster based on QoS requirements. The goal of the proposed scheduling algorithm is to avoid situations in which the system provides a lower performance than desired due to servers' congestion. This is achieved through the implementation of forecasting calculations. Obviously, the increase of the computational cost of the algorithm results in some overhead. This is the reason for designing an adaptive time slot scheduling that sets the execution times of the algorithm depending on the burstiness that is arriving to the system. Therefore, the predictive scheduling algorithm proposed includes an adaptive overhead control. Once defined the scheduling of the algorithm, we design the admission control module based on throughput predictions. The results obtained by several throughput predictors are compared and one of them is selected to be included in our algorithm. The utilisation level that the Web servers will have in the near future is also forecasted and reserved for each service depending on the Service Level Agreement (SLA). Our load balancing strategy is based on a classical policy. Hence, a comparison of several classical load balancing policies is also included in order to know which of them better fits our algorithm. A simulation model has been designed to obtain the results presented in this thesis

A session-based architecture for Internet mobility

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2003.Includes bibliographical references (p. 179-189).The proliferation of mobile computing devices and wireless networking products over the past decade has led to an increasingly nomadic computing lifestyle. A computer is no longer an immobile, gargantuan machine that remains in one place for the lifetime of its operation. Today's personal computing devices are portable, and Internet access is becoming ubiquitous. A well-traveled laptop user might use half a dozen different networks throughout the course of a day: a cable modem from home, wide-area wireless on the commute, wired Ethernet at the office, a Bluetooth network in the car, and a wireless, local-area network at the airport or the neighborhood coffee shop. Mobile hosts are prone to frequent, unexpected disconnections that vary greatly in duration. Despite the prevalence of these multi-homed mobile devices, today's operating systems on both mobile hosts and fixed Internet servers lack fine-grained support for network applications on intermittently connected hosts. We argue that network communication is well-modeled by a session abstraction, and present Migrate, an architecture based on system support for a flexible session primitive. Migrate works with application-selected naming services to enable seamless, mobile "suspend/resume" operation of legacy applications and provide enhanced functionality for mobile-aware, session-based network applications, enabling adaptive operation of mobile clients and allowing Internet servers to support large numbers of intermittently connected sessions. We describe our UNIX-based implementation of Migrate and show that sessions are a flexible, robust, and efficient way to manage mobile end points, even for legacy applications.(cont.) In addition, we demonstrate two popular Internet servers that have been extended to leverage our novel notion of session continuations to enable support for large numbers of suspended clients with only minimal resource impact. Experimental results show that Migrate introduces only minor throughput degradation (less than 2% for moderate block sizes) when used over popular access link technologies, gracefully detects and suspends disconnected sessions, rapidly resumes from suspension, and integrates well with existing applications.by Mark Alexander Connell Snoeren.Ph.D

Network reputation-based quality optimization of video delivery in heterogeneous wireless environments

The mass-market adoption of high-end mobile devices and increasing amount of video traffic has led the mobile operators to adopt various solutions to help them cope with the explosion of mobile broadband data traffic, while ensuring high Quality of Service (QoS) levels to their services. Deploying small-cell base stations within the existing macro-cellular networks and offloading traffic from the large macro-cells to the small cells is seen as a promising solution to increase capacity and improve network performance at low cost. Parallel use of diverse technologies is also employed. The result is a heterogeneous network environment (HetNets), part of the next generation network deployments. In this context, this thesis makes a step forward towards the “Always Best Experience” paradigm, which considers mobile users seamlessly roaming in the HetNets environment. Supporting ubiquitous connectivity and enabling very good quality of rich mobile services anywhere and anytime is highly challenging, mostly due to the heterogeneity of the selection criteria, such as: application requirements (e.g., voice, video, data, etc.); different device types and with various capabilities (e.g., smartphones, netbooks, laptops, etc.); multiple overlapping networks using diverse technologies (e.g., Wireless Local Area Networks (IEEE 802.11), Cellular Networks Long Term Evolution (LTE), etc.) and different user preferences. In fact, the mobile users are facing a complex decision when they need to dynamically select the best value network to connect to in order to get the “Always Best Experience”. This thesis presents three major contributions to solve the problem described above: 1) The Location-based Network Prediction mechanism in heterogeneous wireless networks (LNP) provides a shortlist of best available networks to the mobile user based on his location, history record and routing plan; 2) Reputation-oriented Access Network Selection mechanism (RANS) selects the best reputation network from the available networks for the mobile user based on the best trade-off between QoS, energy consumptions and monetary cost. The network reputation is defined based on previous user-network interaction, and consequent user experience with the network. 3) Network Reputation-based Quality Optimization of Video Delivery in heterogeneous networks (NRQOVD) makes use of a reputation mechanism to enhance the video content quality via multipath delivery or delivery adaptation

Improving Cloud Middlebox Infrastructure for Online Services

Middleboxes are an indispensable part of the datacenter networks that provide high availability, scalability and performance to the online services. Using load balancer as an example, this thesis shows that the prevalent scale-out middlebox designs using commodity servers are plagued with three fundamental problems: (1) The server-based layer-4 middleboxes are costly and inflate round-trip-time as much as 2x by processing the packets in software. (2) The middlebox instances cause traffic detouring en route from sources to destinations, which inflates network bandwidth usage by as much as 3.2x and can cause transient congestion. (3) Additionally, existing cloud providers do not support layer-7 middleboxes as a service, and third-party proxy-based layer-7 middlebox design exhibits poor availability as TCP state stored locally on middlebox instances are lost upon instance failure. This thesis examines the root causes of the above problems and proposes new cloud-scale middlebox design principles that systemically address all three problems. First, to address the performance problem, we make a key observation that existing commodity switches have resources available to implement key layer-4 middlebox functionalities such as load balancer, and by processing packets in hardware, switches offer low latency and high capacity benefits, at no additional cost as the switch resources are idle. Motivated by this observation, we propose the design principle of using idle switch resources to accelerate middlebox functionailites. To demonstrate the principle, we developed the complete L4 load balancer design that uses commodity switches for low cost and high performance, and carefully fuses a few software load balancer instances to provide for high availability. Second, to address the high network overhead problem from traffic detouring through middlebox instances, we propose to exploit the principles of locality and flexibility in placing the middlebox instances and servers to handle the traffic closer to the sources and reduce the overall traffic and link utilization in the network. Third, to provide high availability in a layer 7 middleboxes, we propose a novel middlebox design principle of decoupling the TCP state from middlebox instances and storing it in persistent key-value store so that any middlebox instance can seamlessly take over any TCP connection when middlebox instances fail. We demonstrate the effectiveness of the above cloud-scale middlebox design principles using load balancers as an example. Specifically, we have prototyped the three design principles in three cloud-scale load balancers: Duet, Rubik, and Yoda, respectively. Our evaluation using a datacenter testbed and large scale simulations show that Duet lowers the costs by 12x and latency overhead by 1000x, Rubik further lowers the datacenter network traffic overhead by 3x, and Yoda L7 Load balancer-as-a-service is practical; decoupling TCP state from load balancer instances has a negligible