Energy-efficient wireless communication

In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters

Quality of service over ATM networks

PhDAbstract not availabl

Differentiated services and pricing of the Internet

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 1998.Includes bibliographical references.by Atanu Mukerjee.S.M

Architectures and technologies for quality of service provisioning in next generation networks

A NGN is a telecommunication network that differs from classical dedicated networks because of its capability to provide voice, video, data and cellular services on the same infrastructure (Quadruple-Play). The ITU-T standardization body has defined the NGN architecture in three different and well-defined strata: the transport stratum which takes care of maintaining end-to-end connectivity, the service stratum that is responsible for enabling the creation and the delivery of services, and finally the application stratum where applications can be created and executed. The most important separation in this architecture is relative to transport and service stratum. The aim is to enable the flexibility to add, maintain and remove services without any impact on the transport layer; to enable the flexibility to add, maintain and remove transport technologies without any impact on the access to service, application, content and information; and finally the efficient cohesistence of multiple terminals, access technologies and core transport technologies. The Service Oriented Architecture (SOA) is a paradigm often used in systems deployment and integration for organizing and utilizing distributed capabilities under the control of different ownership domains. In this thesis, the SOA technologies in network architetures are surveyed following the NGN functional architecture as defined by the ITU-T. Within each stratum, the main logical functions that have been the subject of investigation according to a service-oriented approach have been highlighted. Moreover, a new definition of the NGN transport stratum functionalities according to the SOA paradigm is proposed; an implementation of the relevant services interfaces to analyze this approach with experimental results shows some insight on the potentialities of the proposed strategy. Within NGN architectures research topic, especially in IP-based network architectures, Traffic Engineering (TE) is referred to as a set of policies and algorithms aimed at balancing network traffic load so as to improve network resource utilization and guarantee the service specific end-to-end QoS. DS-TE technology extends TE functionalities to a per-class basis implementation by introducing a higher level of traffic classification which associates to each class type (CT) a constraint on bandwidth utilization. These constraints are set by defining and configuring a bandwidth constraint (BC) model whih drives resource utilization aiming to higher load balancing, higher QoS performance and lower call blocking rate. Default TE implementations relies on a centralized approach to bandwidth and routing management, that require external management entities which periodically collect network status information and provide management actions. However, due to increasing network complexity, it is desiderable that nodes automatically discover their environment, self-configure and update to adapt to changes. In this thesis the bandwidth management problem is approached adopting an autonomic and distributed approach. Each node has a self-management module, which monitors the unreserved bandwidth in adjacent nodes and adjusts the local bandwidth constraints so as to reduce the differences in the unreserved bandwidth of neighbor nodes. With this distributed and autonomic algorithm, BC are dinamically modified to drive routing decision toward the traffic balancing respecting the QoS constraints for each class-type traffic requests. Finally, Video on Demand (VoD) is a service that provides a video whenever the customer requests it. Realizing a VoD system by means of the Internet network requires architectures tailored to video features such as guaranteed bandwidths and constrained transmission delays: these are hard to be provided in the traditional Internet architecture that is not designed to provide an adequate quality of service (QoS) and quality of experience (QoE) to the final user. Typical VoD solutions can be grouped in four categories: centralized, proxy-based, Content Delivery Network(CDN) and Hybrid architectures. Hybrid architectures combine the employment of a centralized server with that of a Peer-to-peer (P2P) network. This approach can effectively reduce the server load and avoid network congestions close to the server site because the peers support the delivery of the video to other peers using a cache-and-relay strategy making use of their upload bandwidth. Anyway, in a peer-to-peer network each peer is free to join and leave the network without notice, bringing to the phenomena of peer churns. These dynamics are dangerous for VoD architectures, affecting the integrity and retainability of the service. In this thesis, a study aimed to evaluate the impact of the peer churn on the system performance is proposed. Starting from important relationships between system parameters such as playback buffer length, peer request rate, peer average lifetime and server upload rate, four different analytic models are proposed

Architectures and technologies for quality of service provisioning in next generation networks

A NGN is a telecommunication network that differs from classical dedicated networks because of its capability to provide voice, video, data and cellular services on the same infrastructure (Quadruple-Play). The ITU-T standardization body has defined the NGN architecture in three different and well-defined strata: the transport stratum which takes care of maintaining end-to-end connectivity, the service stratum that is responsible for enabling the creation and the delivery of services, and finally the application stratum where applications can be created and executed. The most important separation in this architecture is relative to transport and service stratum. The aim is to enable the flexibility to add, maintain and remove services without any impact on the transport layer; to enable the flexibility to add, maintain and remove transport technologies without any impact on the access to service, application, content and information; and finally the efficient cohesistence of multiple terminals, access technologies and core transport technologies. The Service Oriented Architecture (SOA) is a paradigm often used in systems deployment and integration for organizing and utilizing distributed capabilities under the control of different ownership domains. In this thesis, the SOA technologies in network architetures are surveyed following the NGN functional architecture as defined by the ITU-T. Within each stratum, the main logical functions that have been the subject of investigation according to a service-oriented approach have been highlighted. Moreover, a new definition of the NGN transport stratum functionalities according to the SOA paradigm is proposed; an implementation of the relevant services interfaces to analyze this approach with experimental results shows some insight on the potentialities of the proposed strategy. Within NGN architectures research topic, especially in IP-based network architectures, Traffic Engineering (TE) is referred to as a set of policies and algorithms aimed at balancing network traffic load so as to improve network resource utilization and guarantee the service specific end-to-end QoS. DS-TE technology extends TE functionalities to a per-class basis implementation by introducing a higher level of traffic classification which associates to each class type (CT) a constraint on bandwidth utilization. These constraints are set by defining and configuring a bandwidth constraint (BC) model whih drives resource utilization aiming to higher load balancing, higher QoS performance and lower call blocking rate. Default TE implementations relies on a centralized approach to bandwidth and routing management, that require external management entities which periodically collect network status information and provide management actions. However, due to increasing network complexity, it is desiderable that nodes automatically discover their environment, self-configure and update to adapt to changes. In this thesis the bandwidth management problem is approached adopting an autonomic and distributed approach. Each node has a self-management module, which monitors the unreserved bandwidth in adjacent nodes and adjusts the local bandwidth constraints so as to reduce the differences in the unreserved bandwidth of neighbor nodes. With this distributed and autonomic algorithm, BC are dinamically modified to drive routing decision toward the traffic balancing respecting the QoS constraints for each class-type traffic requests. Finally, Video on Demand (VoD) is a service that provides a video whenever the customer requests it. Realizing a VoD system by means of the Internet network requires architectures tailored to video features such as guaranteed bandwidths and constrained transmission delays: these are hard to be provided in the traditional Internet architecture that is not designed to provide an adequate quality of service (QoS) and quality of experience (QoE) to the final user. Typical VoD solutions can be grouped in four categories: centralized, proxy-based, Content Delivery Network(CDN) and Hybrid architectures. Hybrid architectures combine the employment of a centralized server with that of a Peer-to-peer (P2P) network. This approach can effectively reduce the server load and avoid network congestions close to the server site because the peers support the delivery of the video to other peers using a cache-and-relay strategy making use of their upload bandwidth. Anyway, in a peer-to-peer network each peer is free to join and leave the network without notice, bringing to the phenomena of peer churns. These dynamics are dangerous for VoD architectures, affecting the integrity and retainability of the service. In this thesis, a study aimed to evaluate the impact of the peer churn on the system performance is proposed. Starting from important relationships between system parameters such as playback buffer length, peer request rate, peer average lifetime and server upload rate, four different analytic models are proposed

Traffic Profiles and Performance Modelling of Heterogeneous Networks

This thesis considers the analysis and study of short and long-term traffic patterns of heterogeneous networks. A large number of traffic profiles from different locations and network environments have been determined. The result of the analysis of these patterns has led to a new parameter, namely the 'application signature'. It was found that these signatures manifest themselves in various granularities over time, and are usually unique to an application, permanent virtual circuit (PVC), user or service. The differentiation of the application signatures into different categories creates a foundation for short and long-term management of networks. The thesis therefore looks from the micro and macro perspective on traffic management, covering both aspects. The long-term traffic patterns have been used to develop a novel methodology for network planning and design. As the size and complexity of interconnected systems grow steadily, usually covering different time zones, geographical and political areas, a new methodology has been developed as part of this thesis. A part of the methodology is a new overbooking mechanism, which stands in contrast to existing overbooking methods created by companies like Bell Labs. The new overbooking provides companies with cheaper network design and higher average throughput. In addition, new requirements like risk factors have been incorporated into the methodology, which lay historically outside the design process. A large network service provider has implemented the overbooking mechanism into their network planning process, enabling practical evaluation. The other aspect of the thesis looks at short-term traffic patterns, to analyse how congestion can be controlled. Reoccurring short-term traffic patterns, the application signatures, have been used for this research to develop the "packet train model" further. Through this research a new congestion control mechanism was created to investigate how the application signatures and the "extended packet train model" could be used. To validate the results, a software simulation has been written that executes the proprietary congestion mechanism and the new mechanism for comparison. Application signatures for the TCP/IP protocols have been applied in the simulation and the results are displayed and discussed in the thesis. The findings show the effects that frame relay congestion control mechanisms have on TCP/IP, where the re-sending of segments, buffer allocation, delay and throughput are compared. The results prove that application signatures can be used effectively to enhance existing congestion control mechanisms.AT&T (UK) Ltd, Englan

Self-Evaluation Applied Mathematics 2003-2008 University of Twente

This report contains the self-study for the research assessment of the Department of Applied Mathematics (AM) of the Faculty of Electrical Engineering, Mathematics and Computer Science (EEMCS) at the University of Twente (UT). The report provides the information for the Research Assessment Committee for Applied Mathematics, dealing with mathematical sciences at the three universities of technology in the Netherlands. It describes the state of affairs pertaining to the period 1 January 2003 to 31 December 2008

End-to-end security in active networks

Active network solutions have been proposed to many of the problems caused by the increasing heterogeneity of the Internet. These ystems allow nodes within the network to process data passing through in several ways. Allowing code from various sources to run on routers introduces numerous security concerns that have been addressed by research into safe languages, restricted execution environments, and other related areas. But little attention has been paid to an even more critical question: the effect on end-to-end security of active flow manipulation. This thesis first examines the threat model implicit in active networks. It develops a framework of security protocols in use at various layers of the networking stack, and their utility to multimedia transport and flow processing, and asks if it is reasonable to give active routers access to the plaintext of these flows. After considering the various security problem introduced, such as vulnerability to attacks on intermediaries or coercion, it concludes not. We then ask if active network systems can be built that maintain end-to-end security without seriously degrading the functionality they provide. We describe the design and analysis of three such protocols: a distributed packet filtering system that can be used to adjust multimedia bandwidth requirements and defend against denial-of-service attacks; an efficient composition of link and transport-layer reliability mechanisms that increases the performance of TCP over lossy wireless links; and a distributed watermarking servicethat can efficiently deliver media flows marked with the identity of their recipients. In all three cases, similar functionality is provided to designs that do not maintain end-to-end security. Finally, we reconsider traditional end-to-end arguments in both networking and security, and show that they have continuing importance for Internet design. Our watermarking work adds the concept of splitting trust throughout a network to that model; we suggest further applications of this idea

Improved learning automata applied to routing in multi-service networks

Multi-service communications networks are generally designed, provisioned and configured, based on source-destination user demands expected to occur over a recurring time period. However due to network users' actions being non-deterministic, actual user demands will vary from those expected, potentially causing some network resources to be under- provisioned, with others possibly over-provisioned. As actual user demands vary over the recurring time period from those expected, so the status of the various shared network resources may also vary. This high degree of uncertainty necessitates using adaptive resource allocation mechanisms to share the finite network resources more efficiently so that more of actual user demands may be accommodated onto the network. The overhead for these adaptive resource allocation mechanisms must be low in order to scale for use in large networks carrying many source-destination user demands. This thesis examines the use of stochastic learning automata for the adaptive routing problem (these being adaptive, distributed and simple in implementation and operation) and seeks to improve their weakness of slow convergence whilst maintaining their strength of subsequent near optimal performance. Firstly, current reinforcement algorithms (the part causing the automaton to learn) are examined for applicability, and contrary to the literature the discretised schemes are found in general to be unsuitable. Two algorithms are chosen (one with fast convergence, the other with good subsequent performance) and are improved through automatically adapting the learning rates and automatically switching between the two algorithms. Both novel methods use local entropy of action probabilities for determining convergence state. However when the convergence speed and blocking probability is compared to a bandwidth-based dynamic link-state shortest-path algorithm, the latter is found to be superior. A novel re-application of learning automata to the routing problem is therefore proposed: using link utilisation levels instead of call acceptance or packet delay. Learning automata now return a lower blocking probability than the dynamic shortest-path based scheme under realistic loading levels, but still suffer from a significant number of convergence iterations. Therefore the final improvement is to combine both learning automata and shortest-path concepts to form a hybrid algorithm. The resulting blocking probability of this novel routing algorithm is superior to either algorithm, even when using trend user demands