... Apache HTTP Server Version 2.2 . ... Filter Types . ... It is important to make the distinction between a protocol and a resource filter. ... If you are writing a filter and you want to know if it is resource or protocol, the correct question to ask is: "Can this filter be removed if the request is redirected to a different resource?" ... So, instead of starting from scratch, we simply point the front of the resource filters for the sub-request to the front of the protocol filters for the old...