On the impact of policing and rate guarantees in Diff-Serv networks: A video streaming application perspective

Over the past few years, there have been a number of proposals aimed at int roducing different levels of service in the Internet. One of the more recen t proposals is the Differentiated Services (Diff-Serv) architecture, and in this paper we explore how the policing actions and associated rate guarant ees provided by the Expedited Forwarding (EF) translate into perceived bene fits for applications that are the presumed users of such enhancements. Spe cifically, we focus on video streaming applications that arguably have rela tively strong service quality requirements, and which should, therefore, st and to benefit from the availability of some form of enhanced service. Our goal is to gain a better understanding of the relation that exists between application level quality measures and the selection of the network level p arameters that govern the delivery of the guarantees that an EF based servi ce would provide. Our investigation, which is experimental in nature, relie s on a number of standard streaming video servers and clients that have bee n modified and instrumented to allow quantification of the perceived qualit y of the received video stream. Quality assessments are performed using a V ideo Quality Measurement tool based on the ANSI objective quality standard. Measurements were made over both a local Diff-Serv testbed and across the QBone, a QoS enabled segment of the Internet2 infrastructure. The paper rep orts and analyzes the results of those measurements.