DNS协议
大约 1 分钟
DNS协议
什么是DNS协议?
域名系统(英语:Domain Name System,缩写:DNS)是互联网的一项服务。它作为将域名和IP地址相互映射的一个分布式数据库,能够使人更方便地访问互联网。DNS使用TCP和UDP端口53。当前,对于每一级域名长度的限制是63个字符,域名总长度则不能超过253个字符。
DNS系统组成
- root 根域名
- 顶级域名
- 二级域名
- 三级域名
- 四级域名
deelmind.com.
. root域名
com 顶级域名
deelmind 二级域名
DNS解析流程
- 本地HOSTS文件解析
C:\Windows\System32\drivers\etc\hosts
# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
DNS Records Types
- A 记录(IPv4 Address Record)
- MX 记录(Mail Exchanger Record)
- NS 记录(Name Server Record)
- PTR 记录(Pointer Record)
- SOA 记录(Start of Authority Record)
- SRV 记录(Service Record)
- TXT 记录(Text Record)
- AAAA 记录(IPv6 Address Record)
- CNAME 记录(Canonical Name Record)