The table below gives a definition of the customizable HTTP proxy profile settings. Both the Management Console field and CLI (config) command text is included.
Table 8-2. Description of Profile Configuration Components
Management Console Checkbox Field
CLI (config) Command
Definition
Pipeline embedded objects in client request
http [no] pipeline client requests
This configuration item applies only to HTML responses. When this setting is enabled, and the object associated with an embedded object reference in the HTML is not already cached, HTTP proxy acquires the object’s content before the client requests the object. This improves response time dramatically. If this setting is disabled, HTTP proxy does not acquire embedded objects until the client requests them.
Section C: Configuring the HTTP Proxy
Pipeline redirects for client request
http [no] pipeline client redirects
When this setting is enabled, and the response of a client request is one of the redirection responses (such as 301, 302, or 307 HTTP response code), then HTTP proxy pipelines the object specified by the Location header of that response, provided that the redirection location is an HTML object. This feature improves response time for redirected URLs. If this setting is disabled, HTTP proxy does not pipeline redirect responses resulting from client requests.
Pipeline embedded objects in prefetch request
http [no] pipeline prefetch requests
This configuration item applies only to HTML responses resulting from pipelined objects. When this setting is enabled, and a pipelined object’s content is also an HTML object, and that HTML object has embedded objects, then HTTP proxy also pipelines those embedded objects. This nested pipelining behavior can occur three levels deep at most. If this setting is disabled, HTTP proxy does not engage in nested pipelining behavior.
Pipeline redirects for prefetch request
http [no] pipeline prefetch
redirects
When this setting is enabled, HTTP proxy pipelines the object specified by a redirect location returned by a pipelined response. If this setting is disabled, HTTP proxy does not try to pipeline redirect locations resulting from a pipelined response.
Substitute Get for IMS http [no] substitute if- modified-since
If the time specified by the If-Modified-Since: header in the client’s conditional request is greater than the last modified time of the object in the cache, it is a strong indication that the copy in the cache is stale. If so, HTTP proxy does a conditional GET to the OCS, based on the last modified time of the cached object.
To control this aspect of the SGOS treatment of the If-Modified-Since: header, disable the Substitute Get for IMS setting. When this setting is disabled, a client time condition greater than the last modified time of the object in the cache does not trigger revalidation of the object.
However, not all objects necessarily have a last- modified time specified by the OCS.
Table 8-2. Description of Profile Configuration Components (Continued)
Management Console Checkbox Field
CLI (config) Command
Section C: Configuring the HTTP Proxy
Substitute Get for HTTP 1.1 conditionals
http [no] substitute conditional
HTTP 1.1 provides additional controls to the client over the behavior of caches concerning the staleness of the object. Depending on various Cache-
Control: headers, the SG appliance can be forced to consult the OCS before serving the object from the cache. For more information about the behavior of various Cache-Control: header values, refer to RFC 2616.
If the Substitute Get for HTTP 1.1 Conditionals setting is enabled, HTTP proxy ignores the following Cache- Control: conditions from the client request: • "max-stale" [ "=" delta-seconds ]
• "max-age" "=" delta-seconds • "min-fresh" "=" delta-seconds • "must-revalidate"
• "proxy-revalidate"
Substitute Get for PNC http [no]
substitute pragma- no-cache
Typically, if a client sends an HTTP GET request with a Pragma: no-cache or Cache-Control: no- cache header (for convenience, both are hereby referred to as PNC), a cache must consult the OCS before serving the content. This means that HTTP proxy always re-fetches the entire object from the OCS, even if the cached copy of the object is fresh. Because of this, PNC requests can degrade proxy performance and increase server-side bandwidth utilization. However, if the Substitute Get for PNC setting is enabled, then the PNC header from the client request is ignored (HTTP proxy treats the request as if the PNC header is not present at all).
Substitute Get for IE reload http [no] substitute ie- reload
Some versions of Internet Explorer issue the Accept: */* header instead of the Pragma: no- cache header when you click Refresh. When an Accept header has only the */* value, HTTP proxy treats it as a PNC header if it is a type-N object. You can control this behavior of HTTP proxy with the Substitute GET for IE Reload setting. When this setting is enabled, the HTTP proxy ignores the PNC interpretation of the Accept: */* header.
Never refresh before expiration
http [no] strict- expiration refresh
Applies only to cached type-T objects. When this setting is enabled, SGOS does not asynchronously revalidate such objects before their specified expiration time. When this setting is disabled, such objects, if they have sufficient relative popularity, can be asynchronously revalidated and can, after a sufficient number of observations of changes, have their estimates of expiration time adjusted
accordingly. Table 8-2. Description of Profile Configuration Components (Continued)
Management Console Checkbox Field
CLI (config) Command
Section C: Configuring the HTTP Proxy