Although proxies provide various capabilities that improve the end user experience with 

features such as caching, they are examined in this dissertation for the ability to analyse 

HTTP request and response information for requests that are directed through them.  

2.5.3.1 Performance and Availability Analysis Capabilities of Proxies 

When user agents are configured to pass requests through a proxy, the proxy emulates the 

target server's interaction with the user agent. It also emulates the user agents interaction 

with the target server. Therefore the proxy is both a client and server. The fact that a proxy 

provides a means to capture these requests and replies means that it offers the possibility of 

analysing various types of information pertaining to a HTTP request. Using proxies to 

capture information in this way has been used for a number of years. The free caching proxy 

software, 

Squid

, offers a vide variety of scripts to analyse and summaries requests to it. 

Other research tested throughput to a remote HTTP proxy [18]. In this case, the proxy 

measures the time that a proxy thread receives a request, to the time the service of the 

request is completed. It also measured the amount of data logged by each request to 

throughput could be calculated. Such research focuses on the performance aspects of HTTP, 

and does not attempt at measuring the availability of an HTTP delivered service. However it 

does offer some interesting insights into the issues involved. 

2.5.3.2 Proxy the End User Experience 

As was stated in the introduction of this dissertation, the possibility of being able to capture 

the performance and availability of a service as perceived by the end user offers a really 

valuable way to analyse a Web delivered service. What the author suggests is that a client 

side proxy could be used to capture information that can then be used to determine how a 

service performs from the end user perspective. Where to position such a proxy that can 

intercept service requests is work examining further. The proxy can in theory be placed 

anywhere between the HTTP server that delivers a service and the end user's browser. 

However, the nearer the proxy is to the end user's browser the more accurate the timing 

information will be. So the advantages of placing the proxy on the client side are: 

The latency between the browser and the proxy are negligible. This means that the proxy 

receives the request from the browser with very little latency and browser receives the