Option 1: Enable "Substitute GET for PNC"
Option 2: Enable "Revalidate Pragma-No-Cache"
Option 1 "Substitute GET for PNC":
Typically, if a client sends an HTTP GET request with a Pragma: no-cache or Cache-Control: no-cache header, 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).
To configure "Substitute GET for PNC": Login to management console > Configuration TAB > Proxy Settings > HTTP proxy > Profiles
Option 2 Enabling Revalidate Pragma-No-Cache:
When the revalidate-pragma-no-cache setting is enabled, a client’s non- conditional PNC-GET request results in a conditional GET request sent to the OCS if the object is already in cache.
The revalidate-pragma-no-cache request allows the OCS to return the 304 Not Modified response, if the content in cache is still fresh.
Thereby, the server-side bandwidth consumed is lesser as the full content is not retrieved again from the OCS.
By default, the revalidate PNC configuration is disabled and is not affected by changes in the top-level profile.
When the Substitute Get for PNC configuration is enabled, the revalidate PNC configuration has no effect.
To configure the revalidate PNC setting:
Note: The revalidate pragma-no-cache setting can only be configured through the CLI.
To enable or disable the revalidate PNC setting, enter one of the following
commands at the (config) command prompt:
SGOS#(config) http revalidate-pragma-no-cache -or-
SGOS#(config) http no revalidate-pragma-no-cache