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常见问题

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Network history

The Genesis of WiFi: From 2 Mbps to Multi-Gigabit, Generation by Generation

WiFi is the one piece of network infrastructure almost nobody thinks about until it stops working - which is exactly the sign of a technology that succeeded. It did not arrive fully formed: the wireless LAN standard went through nearly three decades of generational leaps, each one solving a specific, concrete limitation of the one before it, before it became fast and reliable enough to replace the Ethernet cable entirely for most devices.

Understanding that generational history is more than trivia - it explains why an older device on a network can drag down everyone else's speed, why 5 GHz and 2.4 GHz behave so differently, and why 'WiFi' as a marketing name only appeared years after the underlying standard did.

  1. 1985

    The ISM band is deregulated

    The US FCC opens the 2.4 GHz industrial/scientific/medical band for unlicensed use, the regulatory precondition that made consumer wireless networking possible at all.

  2. 1997

    802.11-1997, the original standard

    The IEEE ratifies the first WiFi standard: up to 2 Mbps, using either infrared or radio in the 2.4 GHz band - technically functional, but too slow and unreliable for real adoption.

  3. 1999

    802.11b and 802.11a

    802.11b reaches 11 Mbps on 2.4 GHz and becomes the first commercially successful version; 802.11a reaches 54 Mbps on the cleaner but shorter-range 5 GHz band the same year.

  4. 1999

    The Wi-Fi Alliance forms

    Equipment vendors create the Wi-Fi Alliance to certify interoperability and coin the consumer-friendly 'Wi-Fi' brand name for what had until then only been known by its IEEE number.

  5. 2003

    802.11g

    Brings 802.11a's 54 Mbps speed to the more common, longer-range 2.4 GHz band, while staying backward-compatible with 802.11b devices - the version that made home WiFi mainstream.

  6. 2003

    WPA replaces WEP

    Wi-Fi Protected Access is introduced after WEP's encryption is publicly broken, followed by the stronger WPA2 (with AES) in 2004.

  7. 2009

    802.11n (WiFi 4)

    Introduces MIMO (multiple antennas transmitting simultaneously) and dual-band 2.4/5 GHz operation, pushing real-world throughput past 100 Mbps for the first time.

  8. 2013

    802.11ac (WiFi 5)

    Moves exclusively to 5 GHz with wider channels and MU-MIMO, crossing the 1 Gbps threshold and finally rivaling wired Gigabit Ethernet.

  9. 2019

    802.11ax (WiFi 6)

    Adds OFDMA (splitting a channel efficiently among many simultaneous devices) and target wake time, designed specifically for dense environments with dozens of connected devices, not just raw speed.

  10. 2024

    802.11be (WiFi 7)

    Introduces the 6 GHz band alongside 2.4/5 GHz, 320 MHz channels, and multi-link operation (using several bands simultaneously for one connection), aiming past 40 Gbps theoretical throughput.

A slow, awkward start

The very first WiFi standard, ratified in 1997, is barely recognizable next to what runs in a modern router. Capped at 2 Mbps and split between an infrared option and an early 2.4 GHz radio option that few vendors implemented compatibly with each other, it was a proof of concept more than a product - genuinely usable wireless networking would need two more years and a second generation of hardware.

That second generation arrived in 1999 as a fork in the road: 802.11b, cheap and long-range on the crowded 2.4 GHz band at 11 Mbps, and 802.11a, faster at 54 Mbps but confined to the higher-frequency 5 GHz band with shorter range and higher cost. 802.11b's price advantage won the consumer market first, which is also why 2.4 GHz networks became so congested for the next two decades - every microwave oven, cordless phone, and Bluetooth device shares that same unlicensed band.

The generation that made WiFi normal

802.11g, standardized in 2003, is arguably the single most consequential release in WiFi's history: it brought 802.11a's 54 Mbps speed onto the more practical 2.4 GHz band, while remaining backward-compatible with the already-installed base of 802.11b devices. That combination of speed, range, and compatibility is what took wireless networking from a business novelty to a default feature of every home router sold from that point forward.

Security caught up the same year. The original WEP encryption scheme had been publicly and thoroughly broken by cryptographers, so the Wi-Fi Alliance rushed out WPA as an interim fix, followed a year later by WPA2 with proper AES encryption - the baseline every legitimate network still uses today, ahead of WPA3's further hardening in 2018.

2.4 GHz offers longer range but only a few non-overlapping channels shared with many other devices; 5 GHz and 6 GHz trade range for far more clean spectrum and dramatically higher throughput.

From one speed to many devices: 802.11n, ac, and ax

802.11n in 2009 is where WiFi stopped being a single radio talking to a single other radio and started being a genuinely multi-antenna system: MIMO (Multiple Input, Multiple Output) uses several antennas to send and receive multiple data streams simultaneously over the same channel, and dual-band operation let a router serve both 2.4 and 5 GHz networks at once for the first time.

802.11ac in 2013 pushed that further with wider 80/160 MHz channels and MU-MIMO (serving several client devices' separate data streams truly simultaneously instead of only one at a time), crossing the symbolic 1 Gbps mark and making WiFi genuinely competitive with wired Gigabit Ethernet for the first time.

802.11ax (WiFi 6) in 2019 is a deliberate change in priorities: instead of chasing peak theoretical speed, it targets the real bottleneck of a modern home or office - dozens of simultaneously connected phones, laptops, and IoT devices. OFDMA slices a channel efficiently between many low-bandwidth devices at once instead of making them each wait their turn, and Target Wake Time lets battery-powered devices negotiate exactly when to check in, extending battery life significantly.

Peak theoretical throughput by generation - each jump reflects a specific technical addition (MIMO, wider channels, MU-MIMO, OFDMA), not simply 'a faster radio'.

Where WiFi 7 takes it next

802.11be (WiFi 7), finalized in 2024, adds an entirely new band - 6 GHz, opened for unlicensed use in most regions only a few years earlier - on top of the existing 2.4 and 5 GHz bands, plus far wider 320 MHz channels. Its most novel feature is Multi-Link Operation: a single device can now use more than one band simultaneously for one connection, dynamically shifting traffic to whichever band has the least congestion at that instant, something no previous generation could do.

Each generation's story is the same pattern repeating: solve interoperability first (802.11-1997), then cost and range (b), then mainstream speed and compatibility (g), then genuine multi-antenna throughput (n, ac), then density and efficiency for dozens of devices (ax), then multi-band flexibility (be). None of it was a single breakthrough - it was three decades of incremental engineering against real, measurable bottlenecks.

要点总结

The practical takeaway for anyone running a network today: a WiFi network's real-world speed is set by its oldest connected device far more than by its newest router, since older generations force the whole network to fall back to slower, more compatible modes in mixed environments. Understanding which generation a device speaks - and which band it's actually using - explains most of the 'why is my WiFi slow' questions this toolkit's Speed Test and My IP tools get asked to help answer.

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我的 IP 检测

自动检测您的公网 IP 地址和网络位置。

打开 NetChecks 时自动加载,无需输入。切换网络或重新连接 VPN 后,点击刷新按钮重新检测。

您的浏览器

一键全面扫描

对一个 IP 或主机名一次性运行所有相关检测:DNS、whois、ping、traceroute、知名端口扫描 (1-1024)、HTTP 头信息和 SSL 证书。

输入域名或 IP 地址并运行,一次性检查 DNS、whois、ping、traceroute、常用端口、HTTP 响应头和 SSL 证书。

大多数检查并行执行,通常在约30秒内完成,若目标响应缓慢或无法访问则更久。

只有在上方的同意复选框被勾选后,端口扫描步骤才会执行——其他所有检查照常执行。

Ping

向主机发送 ICMP 回显请求,以检测其可达性和延迟。

输入主机名或 IP 地址,点击 Ping 发送 ICMP 回显请求并测量往返延迟。

You Host ICMP Echo Request (type 8) ICMP Echo Reply (type 0) measures: RTT · TTL · packet loss

      

深入了解 Ping

定义

Ping通过向目标主机发送ICMP回显请求(Echo Request)报文,并测量ICMP回显应答(Echo Reply)返回所需的时间,来完成最基础的网络连通性测试。它只回答一个问题:"这台设备是否可达,响应速度如何?"ICMP协议(RFC 792)早在1981年就被设计用来在IP网络上承载控制与诊断信息,独立于应用层流量之外——Ping正是它最广为人知、也是普及程度最高的实现,几乎所有操作系统和网络设备从最初版本起就自带这一功能。

工作原理

每个ICMP报文都携带一个TTL(生存时间)字段,每经过一台路由器就减1;一旦在到达目标之前减到0,报文就会被丢弃,并向发送方回送一条错误消息。以毫秒为单位测得的往返时延(RTT)反映的是整个往返路径上累积的网络延迟,而不仅仅是目标附近最后一段的延迟——这一点常被误解,因为Ping结果慢的根本原因可能出现在路径上的任意位置,未必靠近被测服务器。Ping通常会连续发送多个报文而不是只发一个,这样就能区分出偶发的延迟毛刺和持续性的问题,并据此计算出这一批样本的丢包率。

结果解读

稳定且较低的RTT——局域网内几毫秒,同一国家内的目的地10到50毫秒,跨洲链路则明显更高——说明连接状况良好。哪怕只是轻微的丢包(超过1%到2%),对VoIP或交互式远程会话这类对延迟敏感的场景也会造成明显影响,每一个丢失的包都会表现为卡顿或断音。相比稳定但数值较高的延迟,包与包之间延迟波动很大(抖动)对这些场景往往是更严重的问题。"请求超时"表示在规定时间内没有收到应答——可能是主机确实宕机,也可能是防火墙悄悄屏蔽了ICMP,或者路径上某处出现了故障;"目标不可达"则不同,信息量更大:它是路径上某台中间路由器主动回送的消息,明确表示自己无法转发该报文,有助于缩小问题定位范围。

常见误区

最常见的误判是一旦Ping失败就断定主机"宕机",而实际上大量服务器和设备——尤其是部署了严格防火墙策略或托管在主流云服务商那里的——出于策略考虑会主动屏蔽入站ICMP,同时它们提供的实际服务(HTTP、数据库等)完全正常可用。因此,没有收到Ping应答只有在结合其他信号(比如应用本身也无响应)时才具有实际意义。反过来,Ping成功也完全不能保证该主机上运行的应用服务本身工作正常——这是网络栈中两个完全独立的层面。

适用场景

在升级工单之前先做的第一项检查:先确认设备是否有响应,再深入排查。在修改防火墙规则或路由表之后确认连通性,确保改动没有破坏访问。在VoIP上线或运营商链路切换之前建立延迟基线,以便后续出现通话质量投诉时有客观的对比依据。作为MSP并行监控多个客户站点时一种轻量、低开销的周期性健康检查手段,但始终应作为更深层应用级监控的补充,而非替代。

Traceroute(路由追踪)

逐跳追踪到目标主机的网络路径。

输入主机名或 IP 地址并运行,查看本服务器到目标之间的每一跳,以及各跳的延迟。

You TTL=1 TTL=2 TTL=3 Host each hop replies "ICMP Time Exceeded" until TTL reaches the host

      

DNS 查询(Nslookup)

查询 DNS 记录:A、AAAA、MX、TXT、NS、CNAME、SOA、PTR、SRV、CAA。

输入域名,选择记录类型(A、AAAA、MX、TXT、NS、CNAME、SOA、PTR、SRV 或 CAA),然后查询。

You Root .com Auth NS ① query root ② referral → TLD ③ referral → auth NS ④ answer

      

Whois 查询

查询域名或 IP 地址的注册信息。

输入域名或 IP 地址,查询其注册信息:注册商、所有者组织及重要日期。

You Registry RDAP / :43 query: domain / IP reply: registrar, dates, name servers

      

黑名单检测

检查某个 IP 地址或域名是否被列入公共垃圾邮件/滥用黑名单(DNSBL)。

输入 IPv4 地址或域名并运行,即可一次查询 7 个公共 DNSBL/RBL 黑名单 - 每个列表会显示已列入、未列入或检测失败。

You zen.spamhaus.org spamcop.net sorbs.net +4 more reverse-IP DNS query to each DNSBL zone, in parallel

      

TCP 端口扫描

检测主机或 IP 上的 TCP 端口是否开放:常用端口、自定义列表,或完整的 1-65535 范围。

输入主机或 IP,选择常用端口、自定义列表或完整范围,然后扫描查看哪些 TCP 端口有响应。

You 22 open 443 open 3389 closed 8080 closed SYN → SYN-ACK = open · SYN → RST = closed

        
      

HTTP 响应头检测

获取某个 URL 的 HTTP 响应状态码和响应头。

输入网址,获取其 HTTP 响应状态码以及服务器返回的所有响应头。

You Server GET / HTTP/1.1 200 OK + headers Content-Type · Strict-Transport-Security · X-Frame-Options …

      

SSL / TLS 证书检测

检测主机的 TLS 证书:颁发机构、有效期以及剩余天数。

输入主机名,检查其 TLS 证书:颁发者、有效期及距过期的剩余天数。

You Host ClientHello → ← ServerHello + Certificate + Finished Root CA Intermediate Leaf (site) certificate chain of trust · validity dates checked

      

IP 地理位置查询

查询某个 IP 地址的地理位置和网络信息。留空则查询您自己的公网 IP。

输入任意 IP 地址,或留空以查询您自己的 IP,查看其大致位置及网络/ISP 信息。

IP address Geo / RIR database City · Country ASN · Org

        
        
      

子网 / CIDR 计算器

完全在您的浏览器中计算 — 不会向服务器发送任何数据。

输入 IP 地址和 CIDR 前缀(例如 192.168.1.0/24),即时计算网络范围、广播地址和可用主机数量。

network bits (prefix) host bits /24 example — split moves with your prefix

      

网速测试

与本服务器之间的基础下载/上传速度测试(准确性取决于服务器自身的网络带宽)。

点击开始,测量与本服务器之间的下载和上传速度。准确度取决于本服务器自身的网络连接。

You Server ↓ download ↑ upload throughput (Mbps)

      

国家代码词典

ISO 3166-1 alpha-2 国家代码 — 完全在您的浏览器中搜索。

搜索或浏览 ISO 3166-1 alpha-2 国家代码列表,完全在您的浏览器中查询。

国家ISO 代码

国际电话区号词典

按国家划分的国际电话区号 — 完全在您的浏览器中搜索。

按国家搜索或浏览国际拨号代码,完全在您的浏览器中查询。

国家区号

世界时钟

选择一个时区查看当前时间 — 拖动地球即可旋转。

从列表中选择一个时区,或拖动地球仪,查看该地的当前时间。

您的时间
--:--:--
—

—

所选时间
--:--:--
—
— UTC±00:00
与您的时差 —

—

拖动以旋转地球。

法国移动网络状态

法国各运营商(Orange、Free、SFR、Bouygues Telecom)故障或维护中的移动基站,数据来自 Arcep 公开数据。每日更新一次快照,非实时数据流。

按法国运营商浏览移动基站和光纤故障数据——无需输入,根据 ARCEP 公开数据自动更新。

来源:Arcep,「Sites indisponibles」数据集,采用 Licence Ouverte / Etalab 2.0 许可发布——明确允许商业性重用,这与此前使用的 IODA/CAIDA 数据不同。正常/关注/警报 徽章是自制估算(今日故障数与前几日中位数比较),并非 Arcep 官方分类。来源链接见下方。

受影响最多的省份

当前故障或维护中的站点数量,按省份统计。点击上方运营商可筛选。

数据来源: Arcep — Sites indisponibles · 官方网络状态地图


固网(光纤)

各运营商光纤(FTTH)网络质量:故障上报率与装机失败率,数据来自 Arcep 公开数据。月度指标,6个月滚动平均——不像移动部分那样为实时数据。

来源:Arcep,「Qualité des réseaux en fibre optique」数据集,采用 Licence Ouverte / Etalab 2.0 许可发布——明确允许商业性重用。来源链接见下方。

按运营商(母公司)

过去 6 个可用月份的平均值,按基础设施运营商母公司分组。

数据来源: Arcep — Qualité des réseaux en fibre optique