Product Documentation

Built-in Cache Redirection Policies

May 14, 2015

The NetScaler appliance provides built-in cache redirection policies that handle typical cache requests. These policies are based on HTTP methods, the URL or URL tokens of the incoming request, the HTTP version, or the HTTP headers and their values in the request.

Built-in cache redirection policies can be directly bound to a virtual server and do not need further configuration.

Cache redirection policies use two types of NetScaler expressions languages, classic and default syntax. For more information about these languages, see Policies and Expressions.

Built-in Classic Cache Redirection Policies
Built-in cache redirection policies based on classic expressions are called classic cache redirection policies. For a complete description of classic expressions and how to configure them, see Policies and Expressions.

The classic cache redirection policies evaluate basic characteristics of traffic and other data. For example, classic cache redirection policies can determine whether an HTTP request or response contains a particular type of header or URL.

The NetScaler appliance provides the following built-in classic cache redirection policies:

Built-In Policy Name

Description

bypass-non-get

Bypass the cache if the request uses an HTTP method other than GET.

bypass-cache-control

Bypass the cache if the request header contains a Cache-Control: no-cache or Cache-Control: no-store header, or if the HTTP request contains a pragma header.

bypass-dynamic-url

Bypass the cache if the URL suggests that the content is dynamic, as indicated by the presence of any of the following extensions:

  • cgi
  • asp
  • exe
  • cfm
  • ex
  • shtml
  • htx

Also bypass the cache if the URL starts with any of the following:

  • /cgi-bin/
  • /bin/
  • /exec/

bypass-urltokens

Bypass the cache because the request is dynamic, as indicated by one of the following tokens in the URL: ?, !, or =.

bypass-cookie

Bypass the cache for any URL that has a cookie header and an extension other than .gif or .jpg.

Built-in Default Syntax Cache Redirection Policies
Built-in cache redirection policies based on default syntax expressions are called default syntax cache redirection policies. For a complete description of default syntax expressions and how to configure them, see Policies and Expressions.

In addition to the same types of evaluations done by classic cache redirection policies, default syntax cache redirection policies enable you to analyze more data (for example, the body of an HTTP request) and to configure more operations in the policy rule (for example, directing the request to either cache or origin server).

NetScaler appliances provide the following two built-in actions for the default syntax cache redirection policies:
  • CACHE
  • ORIGIN
As implied by their names, they direct the request to the cache server or the origin server, respectively.
Note: If you are using the built-in default syntax cache redirection policy, you cannot modify the action.

The NetScaler appliance provides the following built-in default syntax cache redirection policies:

Built-In Policy Name

Description

bypass-non-get_adv

Bypass the cache if the request uses an HTTP method other than GET.

bypass-cache-control_adv

Bypass the cache if the request header contains a Cache-Control: no-cache or Cache-Control: no-store header, or if the HTTP request contains a pragma header.

bypass-dynamic-url_adv

Bypass the cache if the URL suggests that the content is dynamic, as indicated by the presence of any of the following extensions:

  • cgi
  • asp
  • exe
  • cfm
  • ex
  • shtml
  • htx

Also bypass the cache if the URL starts with any of the following:

  • /cgi-bin/
  • /bin/
  • /exec/

bypass-urltokens_adv

Bypass the cache because the request is dynamic, as indicated by one of the following tokens in the URL: ?, !, or =.

bypass-cookie_adv

Bypass the cache for any URL that has a cookie header and an extension other than .gif or .jpg.

Displaying the Built-in Cache Redirection Policies

Updated: 2013-08-23

You can display the available cache redirection polices by using the command line interface or the configuration utility.

To display the built-in cache redirection policies by using the command line interface

At the command prompt, type:

show cr policy [<policyName>]

Example

 
> show cr policy 
1)       Cache-By-Pass RULE: NS_NON_GET          Policy:bypass-non-get 
2)       Cache-By-Pass RULE: (NS_CACHECONTROL_NOSTORE || NS_CACHECONTROL_NOCACHE || NS_HEADER_PRAGMA)    Policy:bypass-cache-control 
3)       Cache-By-Pass RULE: (NS_EXT_CGI || NS_EXT_ASP || NS_EXT_EXE || NS_EXT_CFM || NS_EXT_EX || NS_EXT_SHTML || NS_EXT_HTX) || (NS_URL_PATH_CGIBIN || NS_URL_PATH_EXEC || NS_URL_PATH_BIN)         Policy:bypass-dynamic-url 
4)       Cache-By-Pass RULE: NS_URL_TOKENS       Policy:bypass-urltokens 
5)       Cache-By-Pass RULE: (NS_HEADER_COOKIE && NS_EXT_NOT_GIF && NS_EXT_NOT_JPEG)     Policy:bypass-cookie 
 Done 
> 

To display the built-in cache redirection policies by using the configuration utility

  1. Navigate to Traffic Management > Cache Redirection > Policies. The configured cache redirection policies appear in the details pane.
  2. Select one of the configured policies to view details.