FTP object management

FTP data that NetCache caches

FTP servers often serve large, cacheable documents. By caching these documents on the NetCache appliance and serving them from the cache, you can save a significant amount of bandwidth.

For transparent or nontransparent FTP

The following table shows the process that NetCache uses to ensure that the object is fresh.

Stage	Description
1	NetCache checks the cache to determine if the object is in the cache.
	If...	Then...
	The object is not in the cache.	NetCache fetches the requested object from the origin server and sends the object to the client. (END)
	The object is in the cache.	NetCache proceeds to Stage 2.
2	NetCache checks the last modified time on the object.
	If...	Then...
	The last modified date of the object in the cache is the same as the last modified date of the object on the server.	NetCache serves the object in the cache to the requesting client. (END)
	The last modified date of the object in the cache is earlier than the last modified date on the object on the server.	NetCache fetches the requested object from the origin server and sends the object to the client. (END)
	No last modified date exists on the object.	NetCache proceeds to Stage 3.
3	NetCache checks the value of the Default Maximum Age option.
	If...	Then...
	The object's age is less than the maximum age value.	NetCache serves the object from the cache to the requesting client. (END)
	The object's age is greater than the maximum age value.	NetCache fetches the requested object from the origin server and sends the object to the client. (END)

If the user reloads an object multiple times successively, NetCache fetches the object from the FTP server.

For FTP over HTTP

NetCache caches the objects fetched from the FTP server. NetCache uses the Default Maximum Age value to ensure the freshness of the FTP data in the cache.

Specifying data that is not to be cached

You can specify data that you do not want NetCache to cache, for example, an executable file (.exe). For information about configuring FTP caching, see the Appliance Manager online Help.

FTP Hierarchy

Hierarchies enable you to define what occurs when the appliance you are configuring cannot resolve a request; that is, what happens when a cache miss occurs.

With no hierarchy configured, the appliance forwards the request to the Internet and attempts to retrieve the requested object from the origin server and return it to the appliance. With a hierarchy configured, the appliance forwards the request to the next level up in the hierarchy, its parent cache. If the parent has it, it returns it to the appliance; if not, it forwards the request up to the next level. After reiterating this process through all configured levels, the request is finally forwarded to the Internet.

For information about configuring an FTP hierarchy, see the Appliance Manager online Help.