Transparent Proxy FAQs

Transparent Proxy FAQs

Transparent proxies improve the quality of service for you by delivering content at higher bandwidth and reducing transmission latency. If we didn't use proxies, customers would be traversing the internet, contending with peak traffic in other countries and under-performing servers and network links. If someone else has already dragged a file down or viewed a page, it's far quicker to serve from the transparent proxy infrastructure than to go and retrieve it again from the World Wide Web.

NOTE: If you host your own Web site and would like to find out how to make your pages more cacheable, visit http://www.mnot.net/cache-docs/.

For more information about transparent proxies, see the FAQs below:

What is a proxy?
What is the difference between a 'proxy' and a 'transparent proxy'?
Why do we have a transparent proxy?
Why can't I see web page updates immediately?
How do I prevent my page from being cached?
How often is the content checked to see if it is fresh?
How effective is caching of Web sites with real-time data such as stock quotes?
Does it slow my access?
Where can I get more information on proxies?


What is a proxy?

Proxies cache, or store, frequently accessed content, then locally fulfill successive requests for the same content, eliminating repetitive transmission of identical content over network links. Transparent proxies on the OptusNet network cache all requests sent on port 80(http). Thus, the complete caching solution comprises a networking component and a cache component.

To localise traffic patterns, the two components work together in the following way:

A user requests a Web page from a browser. The network analyses the request and, based on certain parameters, transparently redirects it to a local network cache. If the cache does not have the Web page, it will make its own Web request to the original Web server. The original Web server delivers the content to the cache, which delivers the content to the client while saving the content in its local storage. That content is now cached. Later, when another user requests the same Web page, the network analyses this request and, based on certain parameters, transparently redirects it to the local network cache. Instead of sending the request over the internet or intranet, the network cache locally fulfills the request. This process reduces download time for the client.

What is the difference between a 'proxy' and a 'transparent proxy'?

There is no difference in the role or the functioning of these proxies. In fact they are in many cases the same machine. The only difference is that you do not have to enter specific network settings or any configuration for your HTTP traffic to be captured by a transparent proxy. Because they are built as part of the network architecture, all port 80 traffic must flow through them.

Why do we have a transparent proxy?

OptusNet uses proxies and caching as part of the managed network solution that we have always raised as the benchmark for internet service. As you can see from the explanation above, caching will improve the users experience of the internet, by locally storing the sites that would normally take a lot longer to load due to the many potential bottlenecks in the internet.

Why can't I see web page updates immediately?

There is no reason why a page should not update immediately if you force your browser to refresh from the site (control-refresh in IE and shift-refresh in Netscape). Remember the transparent proxy is not the only place where caching is done. Copies are saved in your own computer's cache for quick reference, and there may be any number of cache operations at any point in the path from the customer to that site's server. Many Web hosting companies also use cache servers outside their servers to manage traffic and prevent crashing due to frequent processing.

It may also be a case of a poorly coded site. Some sites, by the way they are written, will behave differently in regards to their caching regularity.

How do I prevent my page from being cached?

It is not possible to prevent your site from being cached completely. There are ways to write into the site that the page needs to be re-checked or refreshed every time the page is requested, overriding the regular refresh algorithm. In the real world though, there are very good reasons why you would want your page to be cached. Remember to most customers, speed is everything and web surfers won't wait for slow sites to load, they just go somewhere else. This behaviour is possibly magnified when the person is on the end of a high-speed connection. The only way to accommodate the demand is caching to improve the user experience.

How often is the content checked to see if it is fresh?

There is not a standard simple answer to this question as there are several factors affecting refresh rates! There is an algorithm (calculation) that is performed in the proxies that determines which sites are the busiest, by the number of requests for pages on that site. The busier (or more popular) the site is the more often the proxy checks for freshness. Also, sites can contain information that tells proxies how long to keep a copy of the page before refreshing. Thus some caching can be bypassed by some clever HTML tagging and customers wishing their sites to update more regularly should check the many sites on the internet explaining how to do this.

How effective is caching of Web sites with real-time data such as stock quotes?

Most of the objects that make up a given Web page are static and therefore can be cached. For example, buttons and standard graphics are typically static objects. Other objects on a page can be dynamic and should never be cached (for example, stock prices). Cache engines have the intelligence to determine what objects can be cached and how long they can be cached. This intelligence is derived by obeying the HTTP object header information and by allowing network administrators to control freshness policies. In the case where such a page is cached, only a few dynamic objects need to be retrieved from the origin server, while relatively static objects can be delivered locally from a cache engine. This method provides an effective way to increase network performance while maintaining real-time data integrity.

Does it slow my access?

Exactly the opposite, it significantly speeds up access by removing potential internet bottlenecks.

Where can I get more information on proxies?

Try a search engine for more information.