Download - Video Staging: A Proxy-Server-Based Approach to End-to-End Video Delivery over Wide-Area Networks
Video Staging: A Proxy-Server-Based Approach to End-to-End Video Delivery over Wide-Area Networks
Zhi-Li Zhang, Yuewei Wang,
David H. C. Du, Dongli Su
IEEE/ACM TRANSACTIONS ON NETWORKING,
AUGUEST 2000
Outline Introduction Video Staging: A Single Video Case
– without Smoothing– with Smoothing– Empirical Evaluation
Video Staging: Multiple Video Case– Staging Hot Video Only(SHVO)– Largest Bandwidth Reduction Ratio First(LBRRF)– Empirical Evaluation
Conclusion
Introduction
Video Staging– Reduce the bandwidth requirement in the Backbo
ne WAN – Prefetch a predetermined amount of video data a
nd store them a priori at proxy servers– Only part of a video stream is retrieved directly fr
om the central video server across the backbone WAN
Video Staging(cont.)
– Trading the disk bandwidth of a proxy server for the backbone WAN bandwidth
– The video data are staged at the proxy server on a fairly long period of time instead of caching in and purged out dynamically
Video Staging:A Single Video Case
Video Staging Without Smoothing
i : the index of a video
Ni: total number of frames
F : frame period
sij : the size of jth frame j = 1,…, Ni
Pi : the peak rate of video i
Pi = (max1<=j<=Ni sij) /F
Ci : cut-off rate
0 <= Ci <= Pi*F = max1<=j<=Ni sij
Video Staging Without Smoothing
The upper part consists of a sequence of partial frames with size
sij ,u = ( si
j - Ci )+ j = 1,…, Ni
where x+ = max{x,0}
The lower part consists of a sequence of partial frames with size
sij ,l = si
j - ( sij - Ci )+ j = 1,…, Ni
Video Staging Without Smoothing
The smaller Ci is,the more video data is staged at a proxy server.
As Ci decreases, the lower part of the video becomes less bursty, and eventually approaches to an essentially CBR stream.
The backbone WAN bandwidth requirement from Pi to Ti = Ci / F
The upper part of the video consume
Di = (max1<=j<=Ni sij,u) / F disk bandwidth
Bandwidth reduction ratio Ri = (Pi - Ti) / Di
Video Staging With Smoothing
Cut-Off After Smoothing (CAS)si
~j : referred to as smoothed frames size
Pi : the peak rate of smoothed stream
Ci : cut-off rate
0 <= Ci <= Pi*F = max1<=j<=Ni si~j
Ti = Ci / F amount of backbone WAN bandwidth is reserved
Di = (max1<=j<=Ni si
~j,u) / F amount of disk bandwidth is required in the worst case
Video Staging With Smoothing
Cut-Off Before Smoothing– Smoothing on the Lower Part(SOLP)
Ti = Pi = (max1<=j<=Ni si~j,l) / F
– Smoothing on the Upper Part(SOUP)• Reduce the disk bandwidth required
– Smoothing on the Upper and Lower Parts(SOLP)
Bl = B * (Ci / Pi * F)
Bu = B * (1- (Ci / Pi * F))
Proxy server disk resource requirements for a
single stream
Resource requirements for a single stream
Ratio of backbone WAN bandwidth reduction to proxy server disk bandwidth
Video Staging: Multiple Video Case
Disk bandwidth Total amount of storage space The number of expected concurrent accesses Total reduction in the backbone WAN bandwidth
is maximized
Disk bandwidth constraint
Disk storage constraint
Staging Hot Video Only (SHVO) Regard the user access pattern as the most important fact
or in determining which video to stage at the proxy server. The videos are ordered with respect to their relative “pop
ularity” The number of k hottest videos that can be staged at the p
roxy server is determined
Either a video is entirely staged at the proxy server or not at all
Largest Bandwidth Reduction Ratio First (LBRRF) Use the backbone WAN bandwidth reduction ratio Ri i
n determining which video and what percentage of it to be staged
The burstier video and the video with larger number of concurrent accesses is more likely to have a higher Ri
CPi percentage of video i is staged at the proxy server The algorithm starts with CPi = 0 for all videos and iter
ates by incrementing CPi by P amount at each step.
Impact of proxy server disk resources:clients have no smoothing buffer
Impact of proxy server disk resources:clients have 64KB smoothing buffer
Conclusion
A major objective of our approach is to reduce the backbone WAN bandwidth requirement.
We have designed various video staging methods and evaluated their effectiveness in trading the disk bandwidth of a proxy server for the backbone WAN bandwidth.
The proposed proxy-server-based video staging technique provides a cost-effective and scalable solution to the problem of the end-to-end video delivery over WANs.