计算机网络中的 DNS 与 DHCP 详解

文章目录

[计算机网络中的 DNS 与 DHCP 详解](#计算机网络中的 DNS 与 DHCP 详解)
- 一、域名的分类、作用与常见域名
- - [1. 域名分类体系](#1. 域名分类体系)
  - [2. 顶级域名（TLD）的详细分类](#2. 顶级域名（TLD）的详细分类)
  - - （1）通用顶级域名（gTLD）
    - （2）国家/地区顶级域名（ccTLD）
    - [（3）新通用顶级域名（new gTLD）](#（3）新通用顶级域名（new gTLD）)
  - [3. 二级域名与子域名](#3. 二级域名与子域名)
- [二、DNS 的作用](#二、DNS 的作用)
- - 核心功能
  - [DNS 解析过程简述](#DNS 解析过程简述)
  - [常见 DNS 记录类型](#常见 DNS 记录类型)
- [三、DHCP 的作用](#三、DHCP 的作用)
- - 核心功能
  - [DHCP 工作流程（DORA 四步握手）](#DHCP 工作流程（DORA 四步握手）)
  - [DHCP 分配方式](#DHCP 分配方式)
  - [DHCP 与 DNS 的协作关系](#DHCP 与 DNS 的协作关系)
四、递归查询和迭代查询

一、域名的分类、作用与常见域名

域名（Domain Name）是互联网上用于标识和定位计算机的层次化命名系统，采用点分层次结构，从右向左层级递减。

1. 域名分类体系

层级	名称	示例	说明
第一级	根域名	`.`（通常省略）	域名树的最高层
第二级	顶级域名（TLD）	`.com`、`.cn`	分为 gTLD 和 ccTLD
第三级	二级域名	`example.com`	由注册者申请使用
第四级及以下	子域名	`www.example.com`	由域名所有者自行划分

2. 顶级域名（TLD）的详细分类

（1）通用顶级域名（gTLD）

面向全球开放注册，不限定国家/地区。

域名	全称	用途
.com	commercial	商业机构（最常用）
.net	network	网络服务提供商
.org	organization	非营利组织
.edu	education	教育机构（主要在美国）
.gov	government	政府机构（主要在美国）
.mil	military	美国军事机构
.int	international	国际组织

（2）国家/地区顶级域名（ccTLD）

由 ISO 3166 标准定义，代表特定国家或地区。

域名	代表国家/地区
.cn	中国
.us	美国
.uk	英国
.jp	日本
.de	德国
.hk	中国香港
.tw	中国台湾

（3）新通用顶级域名（new gTLD）

ICANN 于 2012 年起大量开放的新后缀。

域名	用途
.app	应用程序
.blog	博客
.shop	电商/商店
.xyz	通用（因便宜而流行）
.io	技术/初创公司（原为英属印度洋领地）
.ai	人工智能（原为安圭拉）

3. 二级域名与子域名

二级域名 ：注册者向域名注册商购买的唯一标识，如 google.com 中的 google。
子域名 ：域名所有者在 DNS 中自行创建的下一级域名，用于划分不同服务：
- www.example.com --- 网站主站
- mail.example.com --- 邮件服务
- api.example.com --- 接口服务
- cdn.example.com --- 内容分发

二、DNS 的作用

DNS（Domain Name System，域名系统）是互联网的**"电话簿"**，负责将人类易读的域名转换为机器可识别的 IP 地址。

核心功能

功能	说明
域名解析	将域名（如 `www.baidu.com`）解析为对应的 IP 地址（如 `110.242.68.3`）
反向解析	将 IP 地址反向查询为域名（PTR 记录）
负载均衡	通过返回不同 IP 地址，将流量分散到多台服务器
邮件路由	通过 MX 记录指定邮件服务器地址
服务发现	通过 SRV 记录定位特定网络服务

DNS 解析过程简述

复制代码

用户输入 www.example.com
    ↓
浏览器缓存 → 操作系统缓存 → 本地 DNS 服务器（ISP 提供）
    ↓
本地 DNS 向 根域名服务器 查询 → 获取 .com 服务器地址
    ↓
向 .com 顶级域名服务器 查询 → 获取 example.com 服务器地址
    ↓
向 example.com 权威域名服务器 查询 → 获取最终 IP 地址
    ↓
返回 IP 给用户，完成访问

常见 DNS 记录类型

记录类型	作用
A	将域名指向 IPv4 地址
AAAA	将域名指向 IPv6 地址
CNAME	域名别名（指向另一个域名）
MX	邮件交换记录
NS	指定该域名的权威 DNS 服务器
TXT	文本记录（常用于验证域名所有权、SPF 反垃圾邮件）

三、DHCP 的作用

DHCP （Dynamic Host Configuration Protocol，动态主机配置协议）是一种网络管理协议，用于自动为网络中的设备分配 IP 地址及其他网络配置参数。

核心功能

功能	说明
自动分配 IP 地址	设备接入网络时自动获取可用 IP，无需手动配置
分配网络参数	同时分配子网掩码、默认网关、DNS 服务器地址
租约管理	IP 地址按"租期"分配，到期可续租或回收
防止 IP 冲突	由服务器统一分配，避免多台设备使用相同 IP
简化网络管理	大型网络中无需逐台设备手动配置

DHCP 工作流程（DORA 四步握手）

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DHCP 分配方式

方式	说明
自动分配	客户端首次获取 IP 后永久使用
动态分配	IP 有租期限制，到期释放回地址池（最常用）
手动分配	管理员将特定 IP 绑定到特定 MAC 地址（保留地址）

DHCP 与 DNS 的协作关系

DNS 服务器 DHCP 服务器客户端 DNS 服务器 DHCP 服务器客户端 #mermaid-svg-i3XI3cq5NWsUnXHC{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-i3XI3cq5NWsUnXHC .error-icon{fill:#552222;}#mermaid-svg-i3XI3cq5NWsUnXHC .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-i3XI3cq5NWsUnXHC .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-i3XI3cq5NWsUnXHC .marker{fill:#333333;stroke:#333333;}#mermaid-svg-i3XI3cq5NWsUnXHC .marker.cross{stroke:#333333;}#mermaid-svg-i3XI3cq5NWsUnXHC svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-i3XI3cq5NWsUnXHC p{margin:0;}#mermaid-svg-i3XI3cq5NWsUnXHC .actor{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-i3XI3cq5NWsUnXHC text.actor>tspan{fill:black;stroke:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .actor-line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-i3XI3cq5NWsUnXHC .innerArc{stroke-width:1.5;stroke-dasharray:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .messageLine0{stroke-width:1.5;stroke-dasharray:none;stroke:#333;}#mermaid-svg-i3XI3cq5NWsUnXHC .messageLine1{stroke-width:1.5;stroke-dasharray:2,2;stroke:#333;}#mermaid-svg-i3XI3cq5NWsUnXHC #arrowhead path{fill:#333;stroke:#333;}#mermaid-svg-i3XI3cq5NWsUnXHC .sequenceNumber{fill:white;}#mermaid-svg-i3XI3cq5NWsUnXHC #sequencenumber{fill:#333;}#mermaid-svg-i3XI3cq5NWsUnXHC #crosshead path{fill:#333;stroke:#333;}#mermaid-svg-i3XI3cq5NWsUnXHC .messageText{fill:#333;stroke:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .labelBox{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-i3XI3cq5NWsUnXHC .labelText,#mermaid-svg-i3XI3cq5NWsUnXHC .labelText>tspan{fill:black;stroke:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .loopText,#mermaid-svg-i3XI3cq5NWsUnXHC .loopText>tspan{fill:black;stroke:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .loopLine{stroke-width:2px;stroke-dasharray:2,2;stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-i3XI3cq5NWsUnXHC .note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-i3XI3cq5NWsUnXHC .noteText,#mermaid-svg-i3XI3cq5NWsUnXHC .noteText>tspan{fill:black;stroke:none;}#mermaid-svg-i3XI3cq5NWsUnXHC .activation0{fill:#f4f4f4;stroke:#666;}#mermaid-svg-i3XI3cq5NWsUnXHC .activation1{fill:#f4f4f4;stroke:#666;}#mermaid-svg-i3XI3cq5NWsUnXHC .activation2{fill:#f4f4f4;stroke:#666;}#mermaid-svg-i3XI3cq5NWsUnXHC .actorPopupMenu{position:absolute;}#mermaid-svg-i3XI3cq5NWsUnXHC .actorPopupMenuPanel{position:absolute;fill:#ECECFF;box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);filter:drop-shadow(3px 5px 2px rgb(0 0 0 / 0.4));}#mermaid-svg-i3XI3cq5NWsUnXHC .actor-man line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-i3XI3cq5NWsUnXHC .actor-man circle,#mermaid-svg-i3XI3cq5NWsUnXHC line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;stroke-width:2px;}#mermaid-svg-i3XI3cq5NWsUnXHC :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} 请求联网获得配置，开始上网 ① 获取 IP 地址 ② 告知 DNS 服务器地址确认 / 更新域名记录 ③ 返回 IP + DNS 地址 ④ 发起 DNS 查询（访问域名）返回解析结果

DHCP 负责让设备"连上网"（获得 IP 和网络参数）
DNS 负责让设备"找到目的地"（将域名解析为 IP）

四、递归查询和迭代查询

DNS完整流程图：
#mermaid-svg-EDhJD87TLOhcXTen{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-EDhJD87TLOhcXTen .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-EDhJD87TLOhcXTen .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-EDhJD87TLOhcXTen .error-icon{fill:#552222;}#mermaid-svg-EDhJD87TLOhcXTen .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-EDhJD87TLOhcXTen .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-EDhJD87TLOhcXTen .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-EDhJD87TLOhcXTen .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-EDhJD87TLOhcXTen .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-EDhJD87TLOhcXTen .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-EDhJD87TLOhcXTen .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-EDhJD87TLOhcXTen .marker{fill:#333333;stroke:#333333;}#mermaid-svg-EDhJD87TLOhcXTen .marker.cross{stroke:#333333;}#mermaid-svg-EDhJD87TLOhcXTen svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-EDhJD87TLOhcXTen p{margin:0;}#mermaid-svg-EDhJD87TLOhcXTen .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#mermaid-svg-EDhJD87TLOhcXTen .cluster-label text{fill:#333;}#mermaid-svg-EDhJD87TLOhcXTen .cluster-label span{color:#333;}#mermaid-svg-EDhJD87TLOhcXTen .cluster-label span p{background-color:transparent;}#mermaid-svg-EDhJD87TLOhcXTen .label text,#mermaid-svg-EDhJD87TLOhcXTen span{fill:#333;color:#333;}#mermaid-svg-EDhJD87TLOhcXTen .node rect,#mermaid-svg-EDhJD87TLOhcXTen .node circle,#mermaid-svg-EDhJD87TLOhcXTen .node ellipse,#mermaid-svg-EDhJD87TLOhcXTen .node polygon,#mermaid-svg-EDhJD87TLOhcXTen .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-EDhJD87TLOhcXTen .rough-node .label text,#mermaid-svg-EDhJD87TLOhcXTen .node .label text,#mermaid-svg-EDhJD87TLOhcXTen .image-shape .label,#mermaid-svg-EDhJD87TLOhcXTen .icon-shape .label{text-anchor:middle;}#mermaid-svg-EDhJD87TLOhcXTen .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#mermaid-svg-EDhJD87TLOhcXTen .rough-node .label,#mermaid-svg-EDhJD87TLOhcXTen .node .label,#mermaid-svg-EDhJD87TLOhcXTen .image-shape .label,#mermaid-svg-EDhJD87TLOhcXTen .icon-shape .label{text-align:center;}#mermaid-svg-EDhJD87TLOhcXTen .node.clickable{cursor:pointer;}#mermaid-svg-EDhJD87TLOhcXTen .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#mermaid-svg-EDhJD87TLOhcXTen .arrowheadPath{fill:#333333;}#mermaid-svg-EDhJD87TLOhcXTen .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-EDhJD87TLOhcXTen .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-EDhJD87TLOhcXTen .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-EDhJD87TLOhcXTen .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-EDhJD87TLOhcXTen .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-EDhJD87TLOhcXTen .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#mermaid-svg-EDhJD87TLOhcXTen .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-EDhJD87TLOhcXTen .cluster text{fill:#333;}#mermaid-svg-EDhJD87TLOhcXTen .cluster span{color:#333;}#mermaid-svg-EDhJD87TLOhcXTen div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-EDhJD87TLOhcXTen .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-EDhJD87TLOhcXTen rect.text{fill:none;stroke-width:0;}#mermaid-svg-EDhJD87TLOhcXTen .icon-shape,#mermaid-svg-EDhJD87TLOhcXTen .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-EDhJD87TLOhcXTen .icon-shape p,#mermaid-svg-EDhJD87TLOhcXTen .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#mermaid-svg-EDhJD87TLOhcXTen .icon-shape .label rect,#mermaid-svg-EDhJD87TLOhcXTen .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-EDhJD87TLOhcXTen .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-EDhJD87TLOhcXTen .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-EDhJD87TLOhcXTen :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} 🟡 迭代查询区域
🔵 递归查询区域
递归查询

www.example.com?
返回 IP

93.184.216.34
① 问根
去问 .com 服务器
② 问 TLD
去问 example.com
③ 问权威
IP: 93.184.216.34 ✅
C
L
R
T
A

时序图（按时间线展示）：
权威服务器 (example.com) TLD 服务器 (.com) 根服务器本地 DNS 服务器客户端权威服务器 (example.com) TLD 服务器 (.com) 根服务器本地 DNS 服务器客户端 #mermaid-svg-pokLVhqY6kZj8bwS{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-pokLVhqY6kZj8bwS .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-pokLVhqY6kZj8bwS .error-icon{fill:#552222;}#mermaid-svg-pokLVhqY6kZj8bwS .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-pokLVhqY6kZj8bwS .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-pokLVhqY6kZj8bwS .marker{fill:#333333;stroke:#333333;}#mermaid-svg-pokLVhqY6kZj8bwS .marker.cross{stroke:#333333;}#mermaid-svg-pokLVhqY6kZj8bwS svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-pokLVhqY6kZj8bwS p{margin:0;}#mermaid-svg-pokLVhqY6kZj8bwS .actor{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-pokLVhqY6kZj8bwS text.actor>tspan{fill:black;stroke:none;}#mermaid-svg-pokLVhqY6kZj8bwS .actor-line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-pokLVhqY6kZj8bwS .innerArc{stroke-width:1.5;stroke-dasharray:none;}#mermaid-svg-pokLVhqY6kZj8bwS .messageLine0{stroke-width:1.5;stroke-dasharray:none;stroke:#333;}#mermaid-svg-pokLVhqY6kZj8bwS .messageLine1{stroke-width:1.5;stroke-dasharray:2,2;stroke:#333;}#mermaid-svg-pokLVhqY6kZj8bwS #arrowhead path{fill:#333;stroke:#333;}#mermaid-svg-pokLVhqY6kZj8bwS .sequenceNumber{fill:white;}#mermaid-svg-pokLVhqY6kZj8bwS #sequencenumber{fill:#333;}#mermaid-svg-pokLVhqY6kZj8bwS #crosshead path{fill:#333;stroke:#333;}#mermaid-svg-pokLVhqY6kZj8bwS .messageText{fill:#333;stroke:none;}#mermaid-svg-pokLVhqY6kZj8bwS .labelBox{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-pokLVhqY6kZj8bwS .labelText,#mermaid-svg-pokLVhqY6kZj8bwS .labelText>tspan{fill:black;stroke:none;}#mermaid-svg-pokLVhqY6kZj8bwS .loopText,#mermaid-svg-pokLVhqY6kZj8bwS .loopText>tspan{fill:black;stroke:none;}#mermaid-svg-pokLVhqY6kZj8bwS .loopLine{stroke-width:2px;stroke-dasharray:2,2;stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);}#mermaid-svg-pokLVhqY6kZj8bwS .note{stroke:#aaaa33;fill:#fff5ad;}#mermaid-svg-pokLVhqY6kZj8bwS .noteText,#mermaid-svg-pokLVhqY6kZj8bwS .noteText>tspan{fill:black;stroke:none;}#mermaid-svg-pokLVhqY6kZj8bwS .activation0{fill:#f4f4f4;stroke:#666;}#mermaid-svg-pokLVhqY6kZj8bwS .activation1{fill:#f4f4f4;stroke:#666;}#mermaid-svg-pokLVhqY6kZj8bwS .activation2{fill:#f4f4f4;stroke:#666;}#mermaid-svg-pokLVhqY6kZj8bwS .actorPopupMenu{position:absolute;}#mermaid-svg-pokLVhqY6kZj8bwS .actorPopupMenuPanel{position:absolute;fill:#ECECFF;box-shadow:0px 8px 16px 0px rgba(0,0,0,0.2);filter:drop-shadow(3px 5px 2px rgb(0 0 0 / 0.4));}#mermaid-svg-pokLVhqY6kZj8bwS .actor-man line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;}#mermaid-svg-pokLVhqY6kZj8bwS .actor-man circle,#mermaid-svg-pokLVhqY6kZj8bwS line{stroke:hsl(259.6261682243, 59.7765363128%, 87.9019607843%);fill:#ECECFF;stroke-width:2px;}#mermaid-svg-pokLVhqY6kZj8bwS :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} 🔵 递归查询 🟡 迭代查询查询 www.example.com ① 询问根服务器返回 .com TLD 服务器地址 ② 询问 TLD 服务器返回 example.com 权威服务器地址 ③ 询问权威服务器返回 IP: 93.184.216.34 返回最终 IP 地址

分层结构图（展示域名层次）：
#mermaid-svg-ZUTfy7sS6UKv0yKH{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;fill:#333;}@keyframes edge-animation-frame{from{stroke-dashoffset:0;}}@keyframes dash{to{stroke-dashoffset:0;}}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-animation-slow{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 50s linear infinite;stroke-linecap:round;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-animation-fast{stroke-dasharray:9,5!important;stroke-dashoffset:900;animation:dash 20s linear infinite;stroke-linecap:round;}#mermaid-svg-ZUTfy7sS6UKv0yKH .error-icon{fill:#552222;}#mermaid-svg-ZUTfy7sS6UKv0yKH .error-text{fill:#552222;stroke:#552222;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-thickness-normal{stroke-width:1px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-thickness-thick{stroke-width:3.5px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-pattern-solid{stroke-dasharray:0;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-thickness-invisible{stroke-width:0;fill:none;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-pattern-dashed{stroke-dasharray:3;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edge-pattern-dotted{stroke-dasharray:2;}#mermaid-svg-ZUTfy7sS6UKv0yKH .marker{fill:#333333;stroke:#333333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .marker.cross{stroke:#333333;}#mermaid-svg-ZUTfy7sS6UKv0yKH svg{font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:16px;}#mermaid-svg-ZUTfy7sS6UKv0yKH p{margin:0;}#mermaid-svg-ZUTfy7sS6UKv0yKH .label{font-family:"trebuchet ms",verdana,arial,sans-serif;color:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .cluster-label text{fill:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .cluster-label span{color:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .cluster-label span p{background-color:transparent;}#mermaid-svg-ZUTfy7sS6UKv0yKH .label text,#mermaid-svg-ZUTfy7sS6UKv0yKH span{fill:#333;color:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .node rect,#mermaid-svg-ZUTfy7sS6UKv0yKH .node circle,#mermaid-svg-ZUTfy7sS6UKv0yKH .node ellipse,#mermaid-svg-ZUTfy7sS6UKv0yKH .node polygon,#mermaid-svg-ZUTfy7sS6UKv0yKH .node path{fill:#ECECFF;stroke:#9370DB;stroke-width:1px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .rough-node .label text,#mermaid-svg-ZUTfy7sS6UKv0yKH .node .label text,#mermaid-svg-ZUTfy7sS6UKv0yKH .image-shape .label,#mermaid-svg-ZUTfy7sS6UKv0yKH .icon-shape .label{text-anchor:middle;}#mermaid-svg-ZUTfy7sS6UKv0yKH .node .katex path{fill:#000;stroke:#000;stroke-width:1px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .rough-node .label,#mermaid-svg-ZUTfy7sS6UKv0yKH .node .label,#mermaid-svg-ZUTfy7sS6UKv0yKH .image-shape .label,#mermaid-svg-ZUTfy7sS6UKv0yKH .icon-shape .label{text-align:center;}#mermaid-svg-ZUTfy7sS6UKv0yKH .node.clickable{cursor:pointer;}#mermaid-svg-ZUTfy7sS6UKv0yKH .root .anchor path{fill:#333333!important;stroke-width:0;stroke:#333333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .arrowheadPath{fill:#333333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edgePath .path{stroke:#333333;stroke-width:2.0px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .flowchart-link{stroke:#333333;fill:none;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edgeLabel{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-ZUTfy7sS6UKv0yKH .edgeLabel p{background-color:rgba(232,232,232, 0.8);}#mermaid-svg-ZUTfy7sS6UKv0yKH .edgeLabel rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-ZUTfy7sS6UKv0yKH .labelBkg{background-color:rgba(232, 232, 232, 0.5);}#mermaid-svg-ZUTfy7sS6UKv0yKH .cluster rect{fill:#ffffde;stroke:#aaaa33;stroke-width:1px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .cluster text{fill:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH .cluster span{color:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH div.mermaidTooltip{position:absolute;text-align:center;max-width:200px;padding:2px;font-family:"trebuchet ms",verdana,arial,sans-serif;font-size:12px;background:hsl(80, 100%, 96.2745098039%);border:1px solid #aaaa33;border-radius:2px;pointer-events:none;z-index:100;}#mermaid-svg-ZUTfy7sS6UKv0yKH .flowchartTitleText{text-anchor:middle;font-size:18px;fill:#333;}#mermaid-svg-ZUTfy7sS6UKv0yKH rect.text{fill:none;stroke-width:0;}#mermaid-svg-ZUTfy7sS6UKv0yKH .icon-shape,#mermaid-svg-ZUTfy7sS6UKv0yKH .image-shape{background-color:rgba(232,232,232, 0.8);text-align:center;}#mermaid-svg-ZUTfy7sS6UKv0yKH .icon-shape p,#mermaid-svg-ZUTfy7sS6UKv0yKH .image-shape p{background-color:rgba(232,232,232, 0.8);padding:2px;}#mermaid-svg-ZUTfy7sS6UKv0yKH .icon-shape .label rect,#mermaid-svg-ZUTfy7sS6UKv0yKH .image-shape .label rect{opacity:0.5;background-color:rgba(232,232,232, 0.8);fill:rgba(232,232,232, 0.8);}#mermaid-svg-ZUTfy7sS6UKv0yKH .label-icon{display:inline-block;height:1em;overflow:visible;vertical-align:-0.125em;}#mermaid-svg-ZUTfy7sS6UKv0yKH .node .label-icon path{fill:currentColor;stroke:revert;stroke-width:revert;}#mermaid-svg-ZUTfy7sS6UKv0yKH :root{--mermaid-font-family:"trebuchet ms",verdana,arial,sans-serif;} 迭代查询
迭代查询
迭代查询
递归查询
Root
Com
Net
Cn
Auth1
Auth2
🌐 www.example.com

93.184.216.34
📧 mail.example.com
🌐 www.google.com
LocalDNS
Client

对比图（递归 vs 迭代）：
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