671e0429_n___Apache_Software_Foundation__Behavior
[Directive] cache-extension [Behavior] 
Specifies additional extensions to the other cache directives. Extensions might be informational or behavioral. An extended directive is specified in the context of a standard directive, so that applications not understanding the extended directive can at least adhere to the behavior mandated by the standard directive.
Server HTTP Transport - Apache CXF Documentation - Apache Software Foundation