A proxy server acts as a go-between for a browser when it requests information over a network such as the Internet. Institutions use proxy servers because they offer security and performance benefits for groups of people who share the same connection to the Internet.
Normally when you request a document over the Web, your browser talks to the origin server --the computer that has the information--and requests it directly. The server then returns the data to your browser, and your browser displays the data for you. When you use a proxy server, you instruct your browser to contact the proxy instead. Then the proxy server retrieves the information from the origin server, and the proxy delivers the information to your browser.
One benefit that proxy servers offer is data caching. Often, a large group of people sharing the same connection to the Internet will look at many of the same documents. By keeping copies of the documents that it retrieves, the proxy can avoid always having to get the document from the origin server and instead get it from disk. This results not only in faster service for the person requesting the document, but in less traffic going over the group's internet connection.
Note that the WebSTAR Proxy server is implemented for HTTP requests only: it does not provide proxy services for FTP or other protocols.
The other advantage is security. A proxy server can be used to allow a group of people access to network services outside of their local firewall without compromising internal security, or to restrict the Internet sites that a group can access. In addition, you can limit which machines can access the proxy server.
If you expect to view the Proxy Monitor Window or track usage in the Proxy log file, we recommend that you notify your users . People may be very surprised to learn that their web browsing is not private, so it is vital to warn them of this monitoring .
For step-by-step instructions for getting started, see Connect to Your Proxy Server .
Caching is a technique that allows many browsers to share web pages stored in a special database on the server disk. If you have a slow Internet connection, you'll find that retrieving files over your local network is faster than getting them from the original Web server. And because your colleagues are getting more of their data from the cache, the Internet connection is available for those files which are not cached.
To avoid serving obsolete files, the Proxy cache will flush files from the cache on a regular basis. No file will be kept more than the specified maximum length of time (14 days, by default). In addition, when the Proxy cache is full, it will remove unpopular files first, based on the average last use of the files.
Some pages, such as stock quotes, search results, and news headlines, are time-sensitive, and should not be cached. The Proxy cache will not cache any pages that do not have a "Last Modified Date" in the HTTP header. Most pages created by CGIs do not have this field, so they will never be cached.
In addition, some pages include an Expiration Date in the HTTP header, indicating when the data will become obsolete. The Proxy cache will honor that date, and remove the file from the cache on or before the day it expires.
For other pages, the Proxy cache uses an algorithm based on the interval between the "Last Modified Date" field in the HTTP header, and the date that the file is cached. The default Time-To-Live Ratio is " 0.2 ". This means the Proxy cache will flush the file in 2% of the time between when the file was modified and when it was received.
To change the ratio, see Time-To-Live .
For example, if a file created or modified on January 1 and requested on February 11, its age is 42 days. Multiply that age by the Time-To-Live ratio of 0.2, and the result is 8.4, so the file will be flushed on or before February 19.
While these procedures will provide the most recent version of a page in most cases, there are still a few situations where the browser will receive an obsolete page. For example, if a simple page is updated once a year, and the first browser accesses it one day before it is updated, the other browsers will get the obsolete version until the file is flushed from the cache after the maximum length of time.
If someone suspects that they have an obsolete page, they can use the browser's "Super Reload" (usually shift+Reload), so that it will include a "nocache" option in the request. In that case, the WebSTAR Proxy server will pass the request to the origin server, rather than returning the file in the cache.
If there is no super reload, try reloading the page twice. Most browsers send a "nocache" command in the second reload request.
The default location for the cache itself is in Plug-Ins : WebSTAR Proxy Extensions : Cache Files . If you would like to move this to another hard disk, you can make a folder named Cache Files on the other disk, and replace the original folder with an alias to that new folder. The Proxy cache will resolve the alias correctly and access the files on the other disk.
As most cached files are small, the Proxy cache benefits greatly from the smaller block sizes of the Mac OS Extended File Format (also known as HFS Plus), introduced in Mac OS 8.1. If you have a large hard drive (over 1 GB) the files will take up substantially less room in this format--you will regain from 50% to 90% of your disk space, without losing any speed.
In addition, the Proxy cache may be faster if you increase the size of the Mac OS Disk Cache (set in the Memory control panel).
The WebSTAR Proxy cache Window in the WebSTAR Server application displays some information about the number of files cached, the cache efficiency and the total number of bytes sent.
To take advantage of the WebSTAR Proxy server, you must configure the browsers. Find the preferences for your browser, and locate the Proxy panel (usually in the "Networking" section). Select the manual proxy option, and enter the default host name of your WebSTAR primary server (do not use a virtual host name), or use the IP number. Enter the port number that you are using for the WebSTAR Proxy server (the default port is 8000 ), and save the preferences. From that point onward, all requests for URLs beginning in " http:// " from that browser will be made through the Proxy server.
For step-by-step instructions see Connect to Your Proxy Server .
If you have a fast internal network, you can reduce or remove the browser cache on the local disk by changing the browser preference. As the data is stored in the Proxy Server's cache, it doesn't have to be kept on the browser machine.
The WebSTAR Proxy server is a group of Plug-Ins that work together. It is designed this way so third-party developers can add support for more protocols, expanded access control, logging features, and other features. The Plug-Ins are:
These Plug-Ins are stored in a WebSTAR Proxy Extensions folder inside the Plug-Ins folder.