Intel 1520 manual Understanding server acceleration mapping rules

Using map rules

Note

Using reverse-map rules

Understanding server acceleration mapping rules

Rewrite rules each consist of three space-delimited fields: type, target, and replacement.

✔Type indicates the type of rule.

✔Target specifies the URL from which the request originates.

✔Replacement specifies the URL the appliance uses in place of the target URL.

When the appliance receives a request as a server accelerator, it first constructs a complete request URL from the relative URL and its headers. The appliance then compares the complete request URL with its list of target (from) URL addresses, looking for a match. For the request URL to match a target URL, the following conditions must be true:

✔The scheme of both URL addresses must be the same.

✔The host in both URL addresses must be the same.

If the request URL contains an unqualified hostname, it will never match a target URL with a fully qualified host name.

✔The ports in both URL addresses must be the same.

If no port is specified in a URL, the default port for the scheme of the URL is used.

✔The path portion of the target URL must match a prefix of the request URL.

If the appliance finds a match, it translates the request URL into the replacement URL in the rule. It sets the host and path of the request URL to match the replacement URL. The appliance removes the prefix of the path that matched the target URL and substitutes for it the path from the replacement URL.

Cross-scheme mappings are not permitted. For example, you cannot map HTTP requests to FTP replacements.

Reverse mappings rewrite the location headers in origin server responses instead of the headers in the user agent requests. Origin servers use location headers to redirect clients to another location.

For example if there is a directory /pub on an origin server at www.molasses.com, and a user agent sends the request to that server for /pub, the server will probably reply with a redirect to http://www.test.com/pub/ to let the client know that it was a directory it had requested, instead of a document. (A common use of redirects is to normalize URL addresses so that clients can bookmark documents properly.)

The appliance uses reverse mappings to prevent redirects from origin servers from causing clients to bypass the appliance in favor of direct access to the origin servers.

132Intel NetStructure Cache Appliance Administrator’s Guide