published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

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Despite the world-changing success of the Internet, shortcomings in its routing and forwarding system have become increasingly apparent. One symptom is an escalating tension between users and providers over the control of routing and forwarding of packets: providers understandably want to control use of their infrastructure, and users understandably want paths with sufficient quality-of-service (QoS) to improve the performance of their applications. As a result, users resort to various “hacks” such as sending traffic through intermediate end-systems, and the providers fight back with mechanisms to inspect and block such traffic. To enable users and providers to jointly control routing and forwarding policies, recent research has considered various architectural approaches in which provider- level route determination occurs separately from forwarding. With this separation, provider-level path computation and selection can be provided as a centralized service: users (or their applications) send path queries to a path service to obtain provider- level paths that meet their application-specific QoS requirements. At the same time, providers can control the use of their infrastructure by dictating how packets are forwarded across their network. The separation of routing and forwarding offers many advantages, but also brings a number of challenges such as scalability. In particular, the path service must respond to path queries in a timely manner and periodically collect topology information containing load-dependent (i.e., performance) routing information. We present a new design for a path service that makes use of expensive pre- computations, parallel on-demand computations on performance information, and caching of recently computed paths to achieve scalability. We demonstrate that, us- ing commodity hardware with a modest amount of resources, the path service can respond to path queries with acceptable latency under a realistic workload. The ser- vice can scale to arbitrarily large topologies through parallelism. Finally, we describe how to utilize the path service in the current Internet with existing Internet applica- tions.

A common feature of emerging future Internet architectures is the ability for applications to select the path, or paths, their packets take between a source and destination. Unlike the current Internet architecture where routing protocols find a single (best) path between a source and destination, future Internet routing protocols will present applications with a set of paths and allow them to select the most appropriate path. Although this enables applications to be actively involved in the selection of the paths their packets travel, the huge number of potential paths and the need to know the current network conditions of each of the proposed paths will make it virtually impossible for applications to select the best set of paths, or just the best path. To tackle this problem, we introduce a new Network Path Advising Service (NPAS) that helps future applications choose network paths. Given a set of possible paths, the NPAS service helps applications select appropriate paths based on both recent path measurements and end-to-end feedback collected from other applications. We describe the NPAS service abstraction, API calls, and a distributed architecture that achieves scalability by determining the most important things to monitor based on actual usage. By analyzing existing traffic patterns, we will demonstrate it is feasible for NPAS to monitor only a few nodes and links and yet be able to offer advice about the most important paths used by a high percentage of traffic. Finally, we describe a prototype implementation of the NPAS components as well as a simulation model used to evaluate the NPAS architecture.

The Skynet IV satellite will provide a medium for an integrated digital communications network. This will use the packet-oriented techniques employed in many modern communications systems. One important role of the system will be to provide jam-resistant services. The advent of sophisticated electronic jammers has required the application of complex error-correcting codes and data interleaving techniques. When the satellite link forms part of a wider network, these have profound effects upon the performance of the data link protocol. This project has examined some of these effects. Terrestrial data link control protocols were found to be very inefficient, and a number of enhancements to these protocols have been proposed. An implementation of the enhanced protocols has been tested within a simulation environment. The simulator was written in Simula, an object-oriented programming language. The performance of the link was observed to be highly dependent upon the error environment presented by the underlying physical layer service (in this case a frequency-hopped spread spectrum anti-jam satellite circuit). A model of the physical layer was combined with a link layer simulator. The model used an unusual technique to reduce the computational requirements of the simulator. The project revealed that a conventional anti-jam satellite circuit is unsuitable for carriage of packetised data services. However, a number of simple changes to the protocol and error control techniques may yield a significant increase in the performance, permitting use of the service even in the harsh error environments presented by hostile jammers. These results are to be used in the specification of future satellite modems.

Thesis (Ph. D.)--University of Hawaii at Manoa, 1982. / Bibliography: leaves 188-191. / Microfiche. / xi, 191 leaves, bound ill. 29 cm

Thesis (PhD)--University of South Australia, 1993.

Thesis (M.S.)--Ohio University, March, 2000. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, November, 1987. / Title from PDF t.p.