客户端是否可以在生成响应时强制源服务器忽略其缓存？例如，它可以在请求中发送Cache-Control: no-cache吗？RFC似乎只是在响应的上下文中讨论Cache-Control: no-cache，而不是在请求的上下文中。
回答我自己的问题。。。
根据http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.1.6:
A client's request MAY specify the maximum age it is willing to accept of an unvalidated response; specifying a value of zero forces the cache(s) to revalidate all responses.
根据http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9.4
The request includes a "no-cache" cache-control directive [...] The server MUST NOT use a cached copy when responding to such a request.