IJCSNS International Journal of Computer Science and Network Security, VOL.9 No.4, April 2009
158
Manuscript received April 5, 2009
Manuscript revised April 20, 2009
Effects of the coherency on the Performance of the Web
Cache Proxy Server
Angel Vassilev Nikolov,
National University of Lesotho
Summary
We develop an analytical model of the web proxy cache
and obtain the hit ratio in terms of the incoming requests
rate,
replacement
distribution
and
document’s
modification rate. We choose a queuing network to
evaluate the decrease of the response time. Numerical
results show that securing a perfect coherency leads to
performance degradation which could be significant in
extreme cases.
Key words:
web cache coherence protocols, hit ratio, queuing network
1. Introduction
The wide adoption of Internet has fundamentally altered
the ways in which people communicate and conduct
businesses. As
the number of web sites grows
exponentially a
lot of
latencies and bandwidth
consumption are experienced. Many efforts have been
done to make web page delivery to the user faster, to
improve servers’ performance, and to reduce network
traffic. In order to achieve these goals server providers
utilize caching whereby frequently used files are copied
and stored “near” to user on the network [13]. The proxy
server’s role is to accept requests from the users and
forward them on their behalf. If the proxy cache does not
contain the document it makes a request to the remote
server, which replies to the proxy. The proxy sends the file
to the requestor, and stores it locally in a cache. Any
further requests for the same document will be satisfied
from the cache without contacting the origin server, thus
reducing its load and relieving the networks. Caches can
be arranged in hierarchical, distributed or hybrid schemes
to satisfy bigger client community [5, 6, 14].
The effects of caching systems, however, are two-fold. As
time progresses some pages are being modified at the
remot