Dynamic routing of reliability-differentiated connections in WDM optical networks

Master'sMASTER OF ENGINEERIN

Efficient embedding of virtual hypercubes in irregular WDM optical networks

This thesis addresses one of the important issues in designing future WDM optical networks. Such networks are expected to employ an all-optical control plane for dissemination of network state information. It has recently been suggested that an efficient control plane will require non-blocking communication infrastructure and routing techniques. However, the irregular nature of most WDM networks does not lend itself to efficient non-blocking communications. It has been recently shown that hypercubes offer some very efficient non-blocking solutions for, all-to-all broadcast operations, which would be very attractive for control plane implementation. Such results can be utilized by embedding virtual structures in the physical network and doing the routing using properties of a virtual architecture. We will emphasize the hypercube due to its proven usefulness. In this thesis we propose three efficient heuristic methods for embedding a virtual hypercube in an irregular host network such that each node in the host network is either a hypercube node or a neighbor of a hypercube node. The latter will be called a “satellite” or “secondary” node. These schemes follow a step-by-step procedure for the embedding and for finding the physical path implementation of the virtual links while attempting to optimize certain metrics such as the number of wavelengths on each link and the average length of virtual link mappings. We have designed software that takes the adjacency list of an irregular topology as input and provides the adjacency list of a hypercube embedded in the original network. We executed this software on a number of irregular networks with different connectivities and compared the behavior of each of the three algorithms. The algorithms are compared with respect to their performance in trying to optimize several metrics. We also compare our algorithms to an already existing algorithm in the literature

An investigation into the scale-free nature of heterogenous networks.

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 it 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 contains 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 an 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 generators 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

Efficient Passive Clustering and Gateways selection MANETs

Passive clustering does not employ control packets to collect topological information in ad hoc networks. In our proposal, we avoid making frequent changes in cluster architecture due to repeated election and re-election of cluster heads and gateways. Our primary objective has been to make Passive Clustering more practical by employing optimal number of gateways and reduce the number of rebroadcast packets