Cost-Based Cache Replacement and Server Selection for Multimedia Proxy Across Wireless

InternetQian ZhangZhe XiangWenwu ZhuLixin Gao

IEEE Transactions on Multimedia, August 2004

Outline

Introduction Multimedia Proxy Architecture Cost-Based Cache Replacement in the

Single-Server Environment Sever Selection in Multiple Server

Environment Simulation Conclusion

Introduction

Multimedia Proxy Architecture

Scalable Video Structure

Layer 0

Layer 1

Layer 2

Video Object

Key effectiveness of the proxy cacheReplacement Policy

Cache gain : Video object’s contribution of the proxy to achieve high performance

Cost-Based Cache Replacement

Performance metrics of traditional replacement algorithmHit ratio Byte hit ratio

Performance metrics of cost-based replacement algorithmVideo qualityNetwork cost savingStart-up delay

Cost-Based Cache Replacement

Multiple objectives for multimedia proxyDifferent portion of continuous media have

different characteristicsReduce the consumption of network resource

by reducing the throughput of Internet transmission between proxy and server

Cache a video prefix in order to reduce startup latency for streaming.

Different layer have different video-quality impact.

Video-Quality Revenue Rate

Rmse(v) [root-mean-square error] : represents the quality of video object.f (v) : request frequency of the video object

Redundant video object

Network-Saving Revenue RateObjective : reduce the consumption of network resource between proxy and serverThroughput Revenue Rate :

Size (v) : size of the video objectDist (RTT(v)) : distance between the server and proxy

Network-Utilization Revenue Rate :

μ(v, t) : network utilization for video v at time t

Startup Latency Revenue RateLatency between remote video server and proxy dominates end-to-end latency.

Prefix caching is an effective way to reduce startup latency for end clients.

Cost-Based Replacement PolicyTotal revenue rate of video object v

Total revenue rate of redundant video object vR

Cache Gain

Cost-Based Replacement Policy in Multiple Server

: integration network utilization for video v at time t

Video with fewer replicas gets a higher network-utilization revenue reate

(Single Server)(Multiple Server)

Server-Selection Algorithm

Multimedia proxy measures the potential revenue of each candidate video server for the request.

Server-Selection Algorithm

To perform load balance for consumed network resource

Selection Gain

To avoid the overload for the hot link while improving the utilization of the cold link

Simulation

Simulation

Simulation

Simulation

Simulation

Multimedia proxy over wireless Internet where the data cache and computational cache were introduced considering the different characteristics of wireless and Internet links.

For the single server case, novel cost-based replacement so as to improve all three aspects of performance, i.e., video quility.

For the multiservers case, new cost-based server-selection policy for multimedia proxy to improve the video quality.

Conclusion