31 
キャッシュ(ヘッダ)

キャッシュ制御に関わるヘッダ
    cache-directive = cache-request-directive
                                | cache-response-directive

    cache-request-directive =
                                "no-cache"
                              | "no-store"
                              | "max-age" "=" delta-seconds
                              | "max-stale" [ "=" delta-seconds ]
                              | "min-fresh" "=" delta-seconds
                              | "no-transform"
                              | "only-if-cached"
                              | cache-extension