Technical data

68 ServerIron ADX Advanced Server Load Balancing Guide
53-1002435-03
Content-aware cache switching
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NOTE
The server debug-policy-caching command impacts performance and should be used for debugging
purposes only. Output for this command is sent to the BP.
Content-aware cache switching
Content-aware cache switching (CSW in a TCS environment) uses information in the header of an
HTTP request to determine how or if content should be retrieved from a cache server. Using the text
in a URL string, the ServerIron ADX sends a request from a client to a cache server or to the Internet
according to user-defined policies.
You can configure content-aware cache switching on the ServerIron ADX to do the following:
• Group cache servers by content; for example, GIF files can be cached on one cache server and
HTML files on another
• Cause HTTP requests containing a given URL string to alwasys go to the same cache server,
minimizing content duplication among cache servers
• Use information in the URL string or Host header field of an HTTP request to determine how the
requested content should be cached
• Explicitly direct requests for dynamic content to the Internet, rather than to a cache server
• Use directives in the HTTP 1.0 or 1.1 header to determine whether requested content should
be cached
NOTE
Content-aware cache switching utilizes the resilient hashing mechanism as described in “Controlling
traffic distribution among cache servers”.
How content-aware switching works
Content-aware switching (CSW) is the ServerIron ADX's ability to direct HTTP requests to a server, or
group of servers, using information in the text of a URL string. The ServerIron ADX examines the
contents of a URL string and makes a decision about where to send the packet based on selection
criteria in user-defined policies. If text in the URL string matches the selection criteria, the HTTP
request is sent to a server group specified in the policy.
NOTE
"URL string" is defined as the contents of the Request-URI part of the Request-Line in an HTTP
request message. This information usually consists of the absolute pathname (directory and
filename) of a resource; for example,
/doc/ServerIron ADX/1199/url_switching.html.
The URL string can also be the input to a process running on a remote server; for example,
/quote.cgi?s=BRCD&d=1d.
The network location of the resource is specified in the Host header field in an HTTP request
message; for example,
Host: www.brocade.com.