TR-06-4.pdf

``Segment-based streaming media proxy: modeling and optimization"  
 
Songqing Chen, Bo Shen, Susie Wee, and Xiaodong Zhang

IEEE Transactions on Multimedia, Vol. 8, No. 2, 2006, pp. 243-256.  

Abstract

Researchers often use segment-based proxy caching strategies to deliver 
streaming media by partially caching media objects. The existing strategies 
mainly consider increasing the byte hit ratio and/or reducing the client 
perceived startup latency (denoted by the metric delayed startup ratio). 
However, these efforts do not guarantee continuous media delivery 
because the to-be-viewed object segments may not be cached in the proxy 
when they are demanded. The potential consequence is playback jitter at the 
client side due to proxy delay in fetching the uncached segments, which we 
call proxy jitter. Thus, for the best interests of clients, a correct model 
for streaming proxy system design should aim to minimize proxy jitter subject 
to reducing the delayed startup ratio and increasing the byte hit ratio. 
However, we have observed two major pairs of conflicting interests inherent 
in this model: (1) one between improving the byte hit ratio and reducing proxy 
jitter, and (2) the other between improving the byte hit ratio and reducing the delayed startup ratio. In this study, we first propose and anylyze prefetching 
methods for in-time prefetching of uncached segments, which provides insights 
into the first pair of the conflicting interests. Second, to address the second
pair of the conflicting interests, we build a general model to analyze the 
performance objectives. Finally, considering our main objective of minimizing 
proxy jitter and optimizing the two tradeoffs, we propose a new streaming 
proxy system called Hyper Proxy. Synthetic and real workloads are used to 
evaluate our system. The performance results show that Hyper Proxy generates
minimum proxy jitter with a low delayed startup ratio and a small decrease 
of byte hit ratio compared with existing scheme.