Localized Approach to Providing Quality-of-Service

Abstract

The exponential growth of Internet brings to focus the need to control such large networks. It is desirable to find simple local rules and strategies that can produce coherent and purposeful global behavior. The need for such mechanisms arises in a variety of settings. In quality-of-service based routing, paths for flows are selected basedupon the knowledge of resource availability at network nodes and the QoS requirements of flows. The best-path routing schemes gather global network state information and always select the best path for an incoming flow based on this global view. On the other hand, the proportional routing schemes proportion incoming flows among multiple candidate paths. We show that near-optimal proportions can be obtained using only locally collected information and a few good candidate paths can be selected using infrequently exchanged global information. We demonstrate that proportional routing schemes achieve higher throughput with lower overhead than best-path routing schemes. Video delivery for full quality playback requires a certain amount of network bandwidth and client buffer. But when these resources are limited, a naive video transmission may cause packet drops at the network and frame drops at the client, resulting in wastage of resources. To avoid this, a server may need to preemptively discard frames locally taking advantage of application-specific information. We first formulate the optimal selective frame discard problem and then present several efficient heuristic algorithms. We also develop adaptive selective layer discard algorithms for providing smoother quality playback of a layered video. Distributed dynamic channel assignment algorithms run at each base station in a wireless cellular network attempt to reduce the network-wide call blocking and call dropping probabilities while making assignment decisions based on neighborhood information only. They may also reassign channels being used by calls in progress to make room for another call. We propose two channel selection strategies based on localpacking for compact packing of channels. We also present a reassignment based call admission control scheme that dynamically adjusts the number of guard channels reserved for handoffs based on reassignment frequency in the neighborhood.