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Modern networks are a reliable and effective medium for moving large volumes of data, however when considering the exponential growth of content, bandwidth and server availability is a finite resource. In many cases, the same content is being sent to multiple users, each consuming resources. Multicast offers scaling, that allows groups of users to receive common content at little extra network cost. While multicast deployment has been slow in terrestrial networks, the multicast service is ideally suited to IP-based broadband satellite networks. Despite this, many current broadband satellite systems do not provide any or limited support for IP multicast services. This thesis seeks to change this and identifies the protocols required to introduce support for IP multicast in broadband satellite systems. It examines the protocols required, with a focus on IP multicast routing using the Protocol Independent Multicast – Sparse Mode (PIM-SM) routing protocol. The robustness and overhead of the protocol are analyzed. This thesis proposes a set of architectures for the efficient delivery of IP multicast over an interactive satellite network. This thesis considers the key functions required to realize end-to-end IP multicast using the emergent 2nd Generation Digital Video Broadcast Return Link via Satellite (DVB-RCS2) specification. It also considers the differences between DVB-RCS2 and a mobile broadband satellite system and proposes appropriate methods for both use-cases. This facilitates merging satellite access networks with a multicast-enabled Internet backbone, enabling delivery of native IP multicast services to networks connected to a satellite terminal. The return link in a two-way broadband satellite network is often considered an expensive resource, which motivates the efficient use of this resource. This thesis therefore examines the applicability of header compression for a satellite system and proposes the use of Robust Header Compression (ROHC) to improve link efficiency.

This dissertation concerns investigations on two of the most important problems in establishing communication security in computer networks: (1) developing a model which precisely describes the mechanism that enforces the security policy and requirements for a secure network, and (2) designing a key management scheme for establishing a secure session for end-to-end encryption between a pair of communicants. The security mechanism attempts to ensure secure flow of information between entities assigned to different security classes in different computer systems attached to a computer communication network. The mechanism also controls the accesses to the network devices by the subjects (users and processes executed on behalf of the users). The communication security problem is formulated by using a mathematical model which precisely describes the security requirements for the network. The model integrates the notions of access control and information flow control to provide a Trusted Network Base (TNB) for the network. The demonstration of security of the network when the security mechanism is designed following the present model is given by using mathematical induction techniques. The problem of designing key management schemes for establishing end-to-end encrypted sessions between source-destination pairs when the source and the destination are on different networks interconnected via Gateways and intermediate networks is examined. In such an internet environment, the key management problem attains a high degree of complexity due to the differences in the key distribution mechanisms used in the constituent networks and the infeasibility of effecting extensive hardware and software changes to the existing networks. A hierarchical approach for key management is presented which utilizes the existing network specific protocols at the lower levels and protocols between Authentication Servers and/or Control Centers of different networks at the higher levels. Details of this approach are discussed for specific illustrative scenarios to demonstrate the implementational simplicity. A formal verification of the security of the resulting system is also conducted by an axiomatic procedure utilizing certain combinatory logic principles. This approach is general and can be used for verifying the security of any existing key management scheme.

published_or_final_version / abstract / toc / Computer Science and Information Systems / Master / Master of Philosophy

published_or_final_version / Electrical Engineering / Master / Master of Philosophy

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