4447f991_P_Guide___HTTP_General_Headers__HTTP_Cache_Control_Directives_HTTP_Message_Type
[Cache-Control Directive] max-stale [Description] If sent without a parameter, indicates that the client is willing to accept a stale reply (one that has expired). If a numeric parameter is included, it indicates how stale, in seconds, the response may be. [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