Performance Analysis of Transactional Traffic in Mobile Ad-hoc Networks

Mobile Ad Hoc networks (MANETs) present unique challenge to new protocol design, especially in scenarios where nodes are highly mobile. Routing protocols performance is essential to the performance of wireless networks especially in mobile ad-hoc scenarios. The development of new routing protocols requires com- paring them against well-known protocols in various simulation environments. The protocols should be analysed under realistic conditions including, but not limited to, representative data transmission models, limited buffer space for data transmission, sensible simulation area and transmission range combination, and realistic moving patterns of the mobiles nodes. Furthermore, application traffic like transactional application traffic has not been investigated for domain-specific MANETs scenarios. Overall, there are not enough performance comparison work in the past literatures. This thesis presents extensive performance comparison among MANETs comparing transactional traffic including both highly-dynamic environment as well as low-mobility cases

Fairness for ABR multipoint-to-point connections

In multipoint-to-point connections, the traffic at the root (destination) is the combination of all traffic originating at the leaves. A crucial concern in the case of multiple senders is how to define fairness within a multicast group and among groups and point-to-point connections. Fairness definition can be complicated since the multipoint connection can have the same identifier (VPI/VCI) on each link, and senders might not be distinguishable in this case. Many rate allocation algorithms implicitly assume that there is only one sender in each VC, which does not hold for multipoint-to-point cases. We give various possibilities for defining fairness for multipoint connections, and show the tradeoffs involved. In addition, we show that ATM bandwidth allocation algorithms need to be adapted to give fair allocations for multipoint-to-point connections.Comment: Proceedings of SPIE 98, November 199

Design issues in quality of service routing

The range of applications and services which can be successfully deployed in packet-switched networks such as the Internet is limited when the network does nor provide Quality of Service (QoS). This is the typical situation in today's Internet. A key aspect in providing QoS support is the requirement for an optimised and intelligent mapping of customer traffic flows onto a physical network topology. The problem of selecting such paths is the task of QoS routing QoS routing algorithms are intrinsically complex and need careful study before being implemented in real networks. Our aim is to address some of the challenges present m the deployment of QoS routing methods. This thesis considers a number of practical limitations of existing QoS routing algorithms and presents solutions to the problems identified. Many QoS routing algorithms are inherently unstable and induce traffic fluctuations in the network. We describe two new routing algorithms which address this problem The first method - ALCFRA (Adaptive Link Cost Function Routing Algorithm) - can be used in networks with sparse connectivity, while the second algorithm - CAR (Connectivity Aware Routing) - is designed to work well in other network topologies. We also describe how to ensure co-operative interaction of the routing algorithms in multiple domains when hierarchial routing is used and also present a solution to the problems of how to provide QoS support m a network where not all nodes are QoS-aware. Our solutions are supported by extensive simulations over a wide range of network topologies and their performance is compared to existing algorithms. It is shown that our solutions advance the state of the art in QoS routing and facilitate the deployment of QoS support in tomorrow's Internet

Quality of service (QoS) support for multimedia applications in large-scale networks

This dissertation studied issues pertaining to QoS provision for multimedia applications at the application layer. We initially studied Internet routing pathology and Internet routing stability by repeating experimental and analytical methods conducted by Paxson in 1996. No similar study was done in recent years. Our findings show that routing behavior of the Internet in 2006 are different from those reported in 1996 in some important aspects. Second, we investigated different stochastic models (e.g. self-similar processes, Auto-Regressive Integrated Moving-Average (ARIMA)) in order to find a suitable model that describes available bandwidth over time of an end-to-end path between two Internet hosts. Our finding of the suitable model is beneficial to predicting of future values of available bandwidth along an end-to-end path. To the best of our knowledge, no similar study was conducted. Third, we designed and evaluated a new path monitoring algorithm inferring available bandwidth of an end-to-end path without monitoring all the paths to minimize monitoring overhead. Our algorithm does not rely on underlying network-layer topology information as required in topology-aware path monitoring techniques. Finally, to complement the above study, we introduced our multicast protocol named core-set routing for transmitting multimedia data from a set of senders to a set of receivers, taking QoS into account. The protocol is suitable for interactive multi-sender multimedia applications such as video conferencing and network gaming

Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Localised Routing Algorithms in Communication Networks with Quality of Service Constraints. Performance Evaluation and Enhancement of New Localised Routing Approaches to Provide Quality of Service for Computer and Communication Networks.

The Quality of Service (QoS) is a profound concept which is gaining increasing attention in the Internet industry. Best-effort applications are now no longer acceptable in certain situations needing high bandwidth provisioning, low loss and streaming of multimedia applications. New emerging multimedia applications are requiring new levels of quality of services beyond those supported by best-effort networks. Quality of service routing is an essential part in any QoS architecture in communication networks. QoS routing aims to select a path among the many possible choices that has sufficient resources to accommodate the QoS requirements. QoS routing can significantly improve the network performance due to its awareness of the network QoS state. Most QoS routing algorithms require maintenance of the global network¿s state information to make routing decisions. Global state information needs to be periodically exchanged among routers since the efficiency of a routing algorithm depends on link-state information accuracy. However, most QoS routing algorithms suffer from scalability due to the high communication overhead and the high computation effort associated with maintaining accurate link state information and distributing global state information to each node in the network. The ultimate goal of this thesis is to contribute towards enhancing the scalability of QoS routing algorithms. Towards this goal, the thesis is focused on Localised QoS routing algorithms proposed to overcome the problems of using global network state information. Using such an approach, the source node makes routing decisions based on the local state information for each node in the path. Localised QoS routing algorithms avoid the problems associated in the global network state, like high communication and processing overheads. In Localised QoS routing algorithms each source node maintains a predetermined set of candidate paths for each destination and avoids the problems associated with the maintenance of a global network state by using locally collected flow statistics and flow blocking probabilities.Libya's higher educatio

Denial of Service in Web-Domains: Building Defenses Against Next-Generation Attack Behavior

The existing state-of-the-art in the field of application layer Distributed Denial of Service (DDoS) protection is generally designed, and thus effective, only for static web domains. To the best of our knowledge, our work is the first that studies the problem of application layer DDoS defense in web domains of dynamic content and organization, and for next-generation bot behaviour. In the first part of this thesis, we focus on the following research tasks: 1) we identify the main weaknesses of the existing application-layer anti-DDoS solutions as proposed in research literature and in the industry, 2) we obtain a comprehensive picture of the current-day as well as the next-generation application-layer attack behaviour and 3) we propose novel techniques, based on a multidisciplinary approach that combines offline machine learning algorithms and statistical analysis, for detection of suspicious web visitors in static web domains. Then, in the second part of the thesis, we propose and evaluate a novel anti-DDoS system that detects a broad range of application-layer DDoS attacks, both in static and dynamic web domains, through the use of advanced techniques of data mining. The key advantage of our system relative to other systems that resort to the use of challenge-response tests (such as CAPTCHAs) in combating malicious bots is that our system minimizes the number of these tests that are presented to valid human visitors while succeeding in preventing most malicious attackers from accessing the web site. The results of the experimental evaluation of the proposed system demonstrate effective detection of current and future variants of application layer DDoS attacks

A framework for enabling energy efficient semantic views in wireless sensor networks for data intensive applications

Sensor networks have been envisioned to be a promising techniquefor data intensive applications such as disaster management andemergency response and are being designed and deployed for theseapplications. The effectiveness of sensor networksin providing information is determined by human's capacity torecognize and comprehend information from the raw data collected,and act accordingly.Finding relevantinformation from the large amount of data, however, becomes achallenging problem because user interests continues to grow asthe number and variety of sensors increase and users expect toreceive only the data they select to view. Transmitting usersirrelevant data during data processing not only overloads userswith unneeded data but also incurs unnecessary communicationoverhead. Furthermore, the user interests may be correlated when alarge number of users seek information from sensor networks. As aresult, a lot of redundant data transmission can be incurredduring processing in resource-constrained sensor networks. Dataaggregation, though effective in reducing data transmission foraggregated queries, doesn't take the correlation among userinterests into consideration during processing. Therefore,additional techniques need to be proposed to provide efficientinformation delivery for correlated user interests inresource-constrained sensor networks.To bridge the gap between data collected by sensors and the information interests of users, the concept of "semantic view" is proposed in this thesis. The semantic view is a powerful abstraction which allows the fusion of multi-sensor and multi-source data into a virtual data gathering and analysis infrastructure commensurate with the interest of an end user. The main challenge is to enable semantic views in an energy efficient manner in resource constrained sensor networks. To that end, a framework which consists of five protocols and algorithms, "Query Aware Sensing", "Probabilistic Query Dissemination", "Correlated Multi-query Processing", "Location Discovery using Out-of-Range information with multi-lateration" and "End-to-end pairwise key establishment" is presented. In the proposed framework, The ultimate goal is to develop an energy efficient and secure framework towards enabling semantic views in sensor networks for data intensive applications