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这类型的域名怎么解析出来?

  •  
  •   webjin · 2015-07-28 17:42:08 +08:00 · 1313 次点击
    这是一个创建于 3246 天前的主题,其中的信息可能已经有所发展或是发生改变。
    images.12345.com.cn.w.alikunlun.com
    一般的Dns商会支持这么长的解析吗
    redsonic
        1
    redsonic  
       2015-07-28 18:30:32 +08:00
    RFC1035规定每级域名最多63个字符,整个域名不能超过255个字符,域名无论长短 解析过程都一样的。

    2.3.4. Size limits

    Various objects and parameters in the DNS have size limits. They are
    listed below. Some could be easily changed, others are more
    fundamental.

    labels 63 octets or less

    names 255 octets or less

    TTL positive values of a signed 32 bit number.

    UDP messages 512 octets or less

    3. DOMAIN NAME SPACE AND RR DEFINITIONS

    3.1. Name space definitions

    Domain names in messages are expressed in terms of a sequence of labels.
    Each label is represented as a one octet length field followed by that
    number of octets. Since every domain name ends with the null label of
    the root, a domain name is terminated by a length byte of zero. The
    high order two bits of every length octet must be zero, and the
    remaining six bits of the length field limit the label to 63 octets or
    less.

    To simplify implementations, the total length of a domain name (i.e.,
    label octets and label length octets) is restricted to 255 octets or
    less.

    Although labels can contain any 8 bit values in octets that make up a
    label, it is strongly recommended that labels follow the preferred
    syntax described elsewhere in this memo, which is compatible with
    existing host naming conventions. Name servers and resolvers must
    compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
    with zero parity. Non-alphabetic codes must match exactly.
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