QoS routing in packet networks

Abstract

The current best-effort service of the Internet is not sufficient to meet the demands of emerging real-time network applications (e.g., video conferencing, Internet telephony). This has motivated the development of new networking technologies (e.g., Intserv, Diffserv, MPLS) that are geared towards providing quality-of-service (QoS) guarantees (e.g., bandwidth, delay, fitter, reliability) to prospective flows. Various aspects of these technologies are being extensively investigated in the research community. In this dissertation, we focus on the routing aspect, with the objective of providing scalable and computationally efficient solutions. The QoS routing problem involves two tasks: (a) capturing and disseminating the state information of the underlying network; and (b) using this information to compute resource-efficient constrained paths. In the presence of multiple constraints (QoS link parameters), these two tasks become notoriously challenging. We investigate several key issues in QoS routing and discuss how to integrate the provided solutions into evolving state-dependent and hierarchical routing protocols (e.g., PNNI and QoS-extended OSPF). First, we develop a hybrid mechanism based on both flooding and tree-based broadcasting for reliable and efficient dissemination of dynamic link-state parameters, such as bandwidth. Second, we present a scalable, source oriented state aggregation methodology for hierarchical networks. Third, we introduce several heuristics and approximation algorithms for path selection under multiple QoS constraints. Fourth, we consider the path selection problem under inaccurate (probabilistically modeled) state information, and provide a heuristic for a special yet important case of this problem, namely, routing under bandwidth and delay constraints. Finally, we evaluate the performance of the proposed methods through simulations.