The Cache Tab
The cache is a directory on your hard disk used by WinProxy to store web documents. You are not required to have a cache, but caching can speed up access times by returning documents locally rather than from a distant server. Caching also reduces the data load on your Internet connection, which is typically the bottleneck for Internet access.
When a browser requests a document, WinProxy can check to see, without requesting the entire file, if the server has a newer version of the requested files than those already stored in the cache. If the document has not been modified, the server returns a message stating that the document is unchanged. WinProxy then sends the cached copy of the document to the browser. You can alter the configuration so that WinProxy returns the cached copy to the browser without checking its validity.
Disk Space and Ram. If you enable the caching feature, be sure you have plenty of disk space to hold the amount of cache specified. Though the primary cache storage is on the hard disk, some system RAM is also required for cache administration. As a rule of thumb, plan on 1 Meg of RAM beyond normal system requirements for every forty Megs of disk cache specified.
HTTP Documents. The cache is used to store only HTTP documents like web pages and pictures. It won't store FTP files, mail, news groups, or anything retrieved with a secure connection. Documents responding to a query-like those generated using a search engine-are not cached. When using AOL as a provider, anything accessed by AOL software will not be cached (however, web pages accessed with other browsers will be cached).
Most browsers have their own cache; they may save documents that WinProxy won't or may have their own copy of a cached document. When a user clicks her browser's Reload or Refresh button, WinProxy always returns the document from the distant server rather than its local cache.
Documents have defined standard HTTP caching extensions; these are sent to the proxy server and browser as part of the document header and are meant to modify caching behavior. Among these extensions are information on the document type and length, whether the document should be cached, and when it should be considered obsolete.
WinProxy won't place documents into the cache if the web server has instructed it not to do so, and it won't cache documents not reporting content length. It won't automatically download newer versions of these files without user intervention; it uses these rules to determine how to retrieve documents as they are requested by the user's application.
System Clock. WinProxy's ability to accurately verify documents depends on the accuracy of the system clock. If the time on the WinProxy computer is incorrect, or if the time-zone is incorrectly configured, WinProxy won't be able to properly request modified documents. The Internet uses Universal Time (Greenwich Time) as the standard time for all Internet documents and communication. If the time, time-zone, or date is not correctly set on the WinProxy computer, WinProxy calculates the time incorrectly and your document caching malfunctions.
Viewing Cache Contents. If you want to view the contents of the WinProxy cache, or statistics on its usage, request the document http://Proxy.Command/ using a browser on any client machine (If configured to require a password, WinProxy asks for one). You will have three options: View Cache Statistics, Browse Cached Files or Delete The Files From The Cache. This is the only way to view cache statistics.
NOTE:DNS cache functions are also available under proxy.command. Be aware that they'll specifically say "DNS cache"-if the option says just "cache," it refers to the web documents cache.
Other options also available on the Cache Tab under Settings:
Figure 4.21: A generous number of options are available for configuring cache.
Check for newer versions of cached files. This determines how often WinProxy checks for modified files before supplying the requested file to a browser. If Each time the file is requested is selected, WinProxy verifies all documents each time they are requested by a browser. This can significantly slow down access to Internet files, but it guarantees that you always get the most current file. If When the file is older than XX hours is selected, WinProxy only checks for newer files when files are older than the specified time. This value is typically set to 12 or 24 hours, so that documents are verified once a day. This is a good setting, as the majority of web sites are unlikely to change often. However, the value can be set for a time range of one hour to one week.
If a user hits the Reload or Refresh button, WinProxy always retrieves the page from the Internet server, overriding any settings here.
Maximum Cache Size: The slider and edit box allow you to configure cache size. The number displayed in the edit box represents a byte size in kilobytes (1024 bytes). For instance, if you set the size to 100,000 KB, then your cache will be 100 Megabytes large. It's usually impractical to make your cache larger than 100 megabytes, because a large cache reduces system performance. If your cache is too small, however, you may not have enough space to fully optimize usage. Optimal cache size varies widely depending upon a user's needs, but a good starting place would be to allocate five to ten megs for each of your first five users, and a couple of megs for each additional user. If you find that these amounts are too little or too great, you can easily change them later.
Cache Directory: This allows you to change the location of the WinProxy cache. You can type in the new location or press the browse button to find a directory to use for the cache. Remember: if you change the cache location before emptying the cache, you'll need to delete the old cache file directory yourself. You can empty the cache named here by pressing Empty Cache. When you hit "empty cache," give it several minutes to complete. It's deliberately set as a low-level priority, and its got a lot of housekeeping to do as it clears out the cache.
Advanced Cache
The advanced cache options allow you to have a finer degree of control over caching. You can specify the rule to be used for individual sites; for instance you can designate that a specific site be checked for newer files each time, while other sites are only checked once a day.
Figure 4.22: With advanced cache, you can configure the way in which specific sites are handled by WinProxy's Web cache.
As in general caching, this doesn't mean that WinProxy downloads a newer file without being requested. Rather, WinProxy uses a rule table to determine when to verify the "freshness" of documents on specific sites. If ever rules for all sites overlap rules for a specific site, the rule for the specific site will win.
