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.