Forcing HTTP/1.1 proxies to revalidate responses

Document Type Expired Internet-Draft (individual)
Author Jeffrey Mogul 
Last updated 1997-05-28
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The HTTP/1.1 specification [1] currently defines a ``proxy-revalidate'' Cache-control directive, which forces a proxy to revalidate a stale response before using it in a reply. There is no mechanism defined that forces a proxy, but not an end-client, to revalidate a fresh response. The lack of such a mechanism is due to an error in drafting RFC2068, and appears to create problems for use of the Authorization header, the Digest Access Authentication extension [2], the State Management Mechanism [3], and several other proposed extensions. This document discusses the problem and several possible solutions, and proposes to add a new ``s-maxage'' directive as the best available solution.


Jeffrey Mogul (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)