Building Programmable Wireless Networks: An Architectural Survey

In recent times, there have been a lot of efforts for improving the ossified Internet architecture in a bid to sustain unstinted growth and innovation. A major reason for the perceived architectural ossification is the lack of ability to program the network as a system. This situation has resulted partly from historical decisions in the original Internet design which emphasized decentralized network operations through co-located data and control planes on each network device. The situation for wireless networks is no different resulting in a lot of complexity and a plethora of largely incompatible wireless technologies. The emergence of "programmable wireless networks", that allow greater flexibility, ease of management and configurability, is a step in the right direction to overcome the aforementioned shortcomings of the wireless networks. In this paper, we provide a broad overview of the architectures proposed in literature for building programmable wireless networks focusing primarily on three popular techniques, i.e., software defined networks, cognitive radio networks, and virtualized networks. This survey is a self-contained tutorial on these techniques and its applications. We also discuss the opportunities and challenges in building next-generation programmable wireless networks and identify open research issues and future research directions.Comment: 19 page

Optimal Access Point Power Management for Green IEEE 802.11 Networks

In this paper, we present an approach and an algorithm aimed at minimising the energy consumption of enterprise Wireless Local Area Networks (WLANs) during periods of low user activity. We act on two network management aspects: powering off some Access Points (APs), and choosing the level of transmission power of each AP. An efficient technique to allocate the user terminals to the various APs is the key to achieving this goal. The approach has been formulated as an integer programming problem with nonlinear constraints, which comes from a general but accurate characterisation of the WLAN. This general problem formulation has two implications: the formulation is widely applicable, but the nonlinearity makes it NP-hard. To solve this problem to optimality, we devised an exact algorithm based on a customised version of Benders’ decomposition method. The computational results proved the ability to obtain remarkable power savings. In addition, the good performance of our algorithm in terms of solving times paves the way for its future deployment in real WLANs.publishedVersio

Load-Aware Traffic Control in Software-Defined Enterprise Wireless Local Area Networks

With the growing popularity of Bring Your Own Device (BYOD), modern enterprise Wireless Local Area Networks (WLANs) deployments always consist of multiple Access Points (APs) to meet the fast-increasing demand for wireless access. In order to avoid network congestion which leads to issues such as suboptimal Quality of Service (QoS) and degraded user Quality of Experience (QoE), intelligent network traffic control is needed. Software Defined Networking (SDN) is an emerging architecture and intensively discussed as one of the most promising technologies to simplify network management and service development. In the SDN architecture, network management is directly programmable because it is decoupled from forwarding layer. Leveraging SDN to the existing enterprise WLANs framework, network services can be flexibly implemented to support intelligent network traffic control. This thesis studies the architecture of software-defined enterprise WLANs and how to improve network traffic control from a client-side and an AP-side perspective. By extending an existing software-defined enterprise WLANs framework, two adaptive algorithms are proposed to provide client-based mobility management and load balancing. Custom protocol messages and AP load metric are introduced to enable the proposed adaptive algorithms. Moreover, a software-defined enterprise WLAN system is designed and implemented on a testbed. A load-aware automatic channel switching algorithm and a QoS-aware bandwidth control algorithm are proposed to achieve AP-based network traffic control. Experimental results from the testbed show that the designed system and algorithms significantly improve the performance of traffic control in enterprise WLANs in terms of network throughput, packet loss rate, transmission delay and jitter

Topics on modelling and simulation of wireless networking protocols

The use of computer simulation to study complex systems has grown significantly over the past several decades. This is especially true with regard to computer networks, where simulation has become a widespread tool used in academic, commercial and military applications. Computer model representations of communication protocol stacks are used to replicate and predict the behavior of real world counterparts to solve a variety of problems.The performance of simulators, measured in both accuracy of results and run time, is a constant concern to simulation users. The running time for high delity simulation of large-scale mobile ad hoc networks can be prohibitively high. The execution time of propagation e ects calculations for a single transmission alone can grow unmanageable to account for all potential receivers. Discrete event simulators can also su er from excessive generation and processing of events, both due to network size and model complexity. In this thesis, three levels of abstracting the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Request to Send/Clear to Send (RTS/CTS) channel access mechanism are presented. In the process of assessing the abstractions' ability to mitigate runtimecost while retaining comparable results to that of a commercially available simulator, OPNET, the abstractions were found to be better suited to collecting one metric over another.Performance issues aside, simulation is an ideal choice for use in prototyping and developing protocols. The costs of simulation are orders of magnitude smaller than that of network testbeds, especially after factoring in the logistics, maintenance, and space required to test live networks. For instance, Internet Protocol version 6 (IPv6) stateless address autocon guration protocols have yet to be convincingly shown to cope with the dynamic, infrastructure-free environment of Mobile Ad hoc Networks (MANETs). This thesis provides a literature survey of autocon guration schemes designed for MANETs, with particular focus on a stateless autocon guration scheme by Jelger andNoel (SECON 2005). The selected scheme provides globally routable IPv6 pre xes to a MANET attached to the Internet via gateways. Using OPNET simulation, the Jelger-Noel scheme is examined with new cluster mobility models, added gateway mobility, and varied network sizes. Performance of the Jelger-Noel scheme, derived from overhead, autocon gura ion time and pre x stability metrics, was found to be highly dependent on network density, and suggested further re nement before deployment.Finally, in cases where a network testbed is used to test protocols, it is still advantageous to run simulations in parallel. While testbeds can help expose design aws due to code or hardware di erences, discrete event simulation environments can o er extensive debugging capabilities andevent control. The two tools provide independent methods of validating the performance of protocols, as well as providing useful feedback on correct protocol implementation and con guration. This thesis presents the Open Shortest Path First (OSPF) routing protocol and its MANET extensions as candidate protocols to test in simulated and emulated MANETs. The measured OSPF overhead from both environments was used as a benchmark to construct equivalent MANET representations and protocol con guration, made particularly challenging due to the wired nature of the emulation testbed. While attempting to duplicate and validate results of a previous OSPF study, limitations of the simulated implementation of OSPF were revealed.M.S., Electrical Engineering -- Drexel University, 200

Software-Defined Networking: A Comprehensive Survey

peer reviewedThe Internet has led to the creation of a digital society, where (almost) everything is connected and is accessible from anywhere. However, despite their widespread adoption, traditional IP networks are complex and very hard to manage. It is both difficult to configure the network according to predefined policies, and to reconfigure it to respond to faults, load, and changes. To make matters even more difficult, current networks are also vertically integrated: the control and data planes are bundled together. Software-defined networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns, introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper, we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound application programming interfaces (APIs), network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this - ew paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms—with a focus on aspects such as resiliency, scalability, performance, security, and dependability—as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment

Interim research assessment 2003-2005 - Computer Science

This report primarily serves as a source of information for the 2007 Interim Research Assessment Committee for Computer Science at the three technical universities in the Netherlands. The report also provides information for others interested in our research activities