4447f991_P_Guide___HTTP_General_Headers__HTTP_Cache_Control_Directives_HTTP_Message_Type
[Cache-Control Directive] only-if-cached [Description] Used only in special circumstances, this directive forces the reply to come from a cache only; the content may not come from the actual specified HTTP server. [HTTP Message Type] 
Request
R e q u e s t o r R e s p o n s e
R e s p o n s e
R e q u e s t
The TCP/IP Guide - HTTP General Headers
HTTP Message Type