控制是直接制定请求的处理的头字段。

    1.    +-------------------+--------------------------+
    2.    | Header Field Name | Defined in...            |
    3.    +-------------------+--------------------------+
    4.    | Cache-Control     | Section 5.2 of [RFC7234] |
    5.    | Expect            | Section 5.1.1            |
    6.    | Host              | Section 5.4 of [RFC7230] |
    7.    | Max-Forwards      | Section 5.1.2            |
    8.    | Pragma            | Section 5.4 of [RFC7234] |
    9.    | Range             | Section 3.1 of [RFC7233] |
    10.    | TE                | Section 4.3 of [RFC7230] |
    11.    +-------------------+--------------------------+