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An investigation into the scale-free nature of heterogeneous networks

Spencer, J.J.L.; (2009) An investigation into the scale-free nature of heterogeneous networks. Doctoral thesis, UCL (University College London).

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Abstract

In order to support a wide variety of services, to different user types, and under a variety of geographic situations, telecommunications networks are typically composed of a variety of layers and heterogeneous technologies. Layers (in terms of the OSI 7 layer model) such as the transmission layer (e.g. WDM), the data link layer (also known as the transport network e.g. SDH, Ethernet) and the network layer (e.g. IP). These layers may also contain logical layers within them such as virtual paths, as well as overlay networks such as a peer-to-peer system. No single layer is independent of the adjacent layer and the provisioning requirements of one layer become the demand on the layer below. Similarly the available resources become the delivered quality of service to the layer above. This thesis is concerned with the design aspects of various layers and how they affect each other’s topology. The thesis’ main focus is topological analysis and modelling of layers, and its presents a detailed analysis of a deployed national SDH network, examining bandwidth distribution, topology, geography and the demand pattern. The thesis finds that even the strictly planned and provisioned SDH network, whose architecture contain explicit structures and hierarchy, has notable power-law traits in various metrics of the topology; traits similar to those which have been shown to exist in the Internet, as well as non-technological networks such as social graphs. There is also and examination of the protocols and architectures of the IP and SDH standards for features that affect topological development. With a better understanding of the layers, design goals and assumptions are deduced and implemented in a new topology simulator called MITIE. MITIE (Modular Inter-layer feedback Topology InvEstigation tool and simulator) is a tool designed to investigate inter-layer feedback and differs from existing topology generator in that it considers the effect of serviced demands and allows the capacity usage to affect the further development of the topology. The thesis presents results from a series of experiments with MITIE and demonstrates that as the network is re-designed to accommodate demand, it can tend to power-law compliant topologies under the correct circumstances. Such a reactive topology model could also be used to investigate the effect of topological change and the effect of increasing the number of layers (such as adding MPLS), or the use of peer-to-peer overlay networks, or the decrease of the number of layers (IP over WDM). The model could also be used to investigate link and node failure/addition and the real effect which will propagate through the rest of the multi-layer network.

Type:Thesis (Doctoral)
Title:An investigation into the scale-free nature of heterogeneous networks
Language:English
Additional information:Authorisation for digitisation not received
UCL classification:UCL > School of BEAMS > Faculty of Engineering Science > Electronic and Electrical Engineering

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