Quality of Service Evaluations of Multicast Streaming Protocols

Complete Citation

Haonan Tan , Derek L. Eager , Mary K. Vernon , Hongfei Guo, Quality of service evaluations of multicast streaming protocols, Proceedings of the 2002 ACM SIGMETRICS international conference on Measurement and modeling of computer systems, June 15-19, 2002, Marina Del Rey, California
DOI Link

Abstract

Recently proposed scalable on-demand streaming protocols have previously been evaluated using a system cost measure termed the "required server bandwidth". For the scalable protocols that provide immediate service to each client when the server is not overloaded, this paper develops simple analytic models to evaluate two client-oriented quality of service metrics, namely (1) the mean client waiting time in systems where clients are willing to wait if a (well-provisioned) server is temporarily overloaded, and (2) the fraction of clients who balk (i.e., leave without receiving their requested media content) in systems where the clients will tolerate no or only very low service delays during a temporary overload. The models include novel approximate MVA techniques that appear to extend the range of applicability of customized AMVA to include questions focussed on state probabilities rather than on mean values, and to systems in which the operating points of interest do not include substantial client queues. For example, the new AMVA models accurately estimate the server bandwidth needed to achieve a balking rate as low as one in ten thousand. The analytic models can easily be applied to determine the server bandwidth needed for a given number of media files, anticipated total client request rate and file access frequencies, and target balking rate or mean wait. Results show that (a) scalable media servers that are configured with the "required server bandwidth" defined in previous work have low mean wait but may have unacceptably high client balking rates (i.e., greater than one in twenty), (b) for high to moderate client load, only a 10 - 50% increase in the previously defined required server bandwidth is needed to achieve a very low balking rate (e.g., one in ten thousand), and (c) media server performance (either mean wait or balking rate) degrades rapidly if the actual client load is more than 10% greater than the anticipated load.

Annotations

This is one of the first works I have encountered which examines Quality of Service for clients of multicast protocols. Specifically, the authors address:
- Mean waiting time for a client (balking rate) before they give up
- Server Bandwidth's affect on balking rate
- Unexpectedly high client arrival rate's affect on balking rate
Our service (TailSync? ) is designed to provide key advantages in such measures, as it will provide immediate service to client who otherwise would be waiting, and potentially balk.
A large portion of the work is derived equations relating arrival rates, service rates, bandwidths, and balking rates mathematically. Although we do not plan to incorporate the same mathematical rigor into our paper, the work done here will provide insight and direction in defining accepted standards of performance.

-- DavidMoore - 19 Dec 2007