3.4 · Network hardware
3.4 · 网络硬件
How devices are found on a network
网络中的设备如何被找到
The card that lets a device join a network, the two addresses that identify it, and the device that joins a home network to the wider internet.
让设备加入网络的网卡、标识设备的两种地址,以及将家庭网络连接到更广阔互联网的设备。
Explainer · 3.4.1
讲解 · 3.4.1
The network interface card (NIC)
网络接口卡(NIC)
A network interface card (NIC) is the hardware a device needs to connect to a network. It is usually built into the device. It carries the device’s MAC address, set when the card was made.
网络接口卡(NIC)是设备连接到网络所需的硬件。它通常内置在设备中,并携带该设备的MAC 地址,该地址在网卡生产时就已设定。
The NIC lets a device join a network. It does not “connect to the internet” by itself, and it is not what assigns the IP address, the network does that.
NIC 让设备能够加入网络。它本身并不"连接到互联网",也不负责分配 IP 地址,分配 IP 地址是网络的工作。
Explainer · 3.4.2
讲解 · 3.4.2
The MAC address
MAC 地址
A MAC (media access control) address identifies a specific piece of network hardware. Its purpose is to uniquely identify a device on a network. Its characteristics:
MAC(媒体访问控制)地址用于标识某一特定的网络硬件。它的用途是在网络中唯一地标识一台设备。它的特征如下:
| Characteristic | 特征 | Detail | 细节 |
|---|---|---|---|
| Set at manufacture | 生产时设定 | given to the NIC when it is made; it does not normally change | 在网卡制造时被赋予,通常不会改变 |
| Written in hexadecimal | 以十六进制书写 | usually shown as six pairs of hex digits | 通常显示为六组十六进制数字对 |
| Two parts | 分为两部分 | the first half is the manufacturer code; the second half is the serial code of that individual device | 前半部分是制造商代码;后半部分是该设备的序列代码 |
Asked for the characteristics of a MAC address, do not answer with its purpose (“it uniquely identifies a device”). Characteristics are: hexadecimal, set at manufacture, manufacturer code plus serial code.
若被问及 MAC 地址的特征,不要回答它的用途("它能唯一标识一台设备")。特征是:十六进制、生产时设定、由制造商代码加序列代码组成。
Try it yourself
动手试试
Inside a MAC address
MAC 地址的内部结构
Click the first half and the second half to see what each part is for.
点击前半部分和后半部分,查看每一部分的作用。
Explainer · 3.4.3
讲解 · 3.4.3
The IP address
IP 地址
An IP (internet protocol) address is the address a device is given on a network, so that data can be routed to it. It is allocated by the network (a router on a local network, or the ISP for the public address), and it can be static or dynamic.
IP(互联网协议)地址是设备在某个网络中被赋予的地址,以便数据能被路由到该设备。它由网络分配(本地网络中由路由器分配,公网地址则由 ISP 分配),并且可以是静态或动态的。
IPv4 and IPv6
IPv4 与 IPv6
| IPv4 | IPv4 | IPv6 | IPv6 | ||
|---|---|---|---|---|---|
| Length | 长度 | 32 bits | 128 bits | ||
| Written as | 书写方式 | four groups, in denary, separated by dots, e.g. 254.25.28.77 | 四组十进制数字,以点号分隔,例如 254.25.28.77 |
eight groups, in hexadecimal, separated by colons, e.g. A8FB:7A88:…:F0FA | 八组十六进制数字,以冒号分隔,例如 A8FB:7A88:…:F0FA |
| Capacity | 容量 | about 4.3 billion addresses, which are running out | 约 43 亿个地址,正在逐渐耗尽 | vastly more; also has built-in authentication and more efficient routing | 数量大得多;还内置了身份验证,并有更高效的路由方式 |
Static and dynamic
静态与动态
| Static | 静态 | Dynamic | 动态 | ||
|---|---|---|---|---|---|
| Changes? | 是否变化? | fixed, always the same | 固定不变,始终相同 | can be different each time the device connects | 设备每次连接时可能不同 |
| Assigned | 分配方式 | set permanently for the device | 为该设备永久设定 | assigned automatically each time, by DHCP | 每次由 DHCP 自动分配 |
| Suits | 适用对象 | servers hosting a website, database or FTP, which must be found at the same address | 托管网站、数据库或 FTP 的服务器,它们必须始终能在同一地址被找到 | ordinary home and office devices; gives a little more privacy | 普通的家用和办公设备;能带来更多一点的隐私 |
If a question asks for the characteristics of an IPv4 address, say the IPv4-specific things: 32 bits, four denary groups, dot-separated. Generic “an IP address identifies a device” will not get the mark. And read whether it wants characteristics, a difference, or an advantage of IPv6: they are different answers.
如果题目要求说出 IPv4 地址的特征,应说出 IPv4 特有的内容:32 位、四组十进制数字、以点号分隔。笼统地说"IP 地址标识一台设备"是不会得分的。同时要看清题目要求的是特征、区别,还是 IPv6 的优点:这些是不同的答案。
Try it yourself
动手试试
IPv4, IPv6, static, dynamic
IPv4、IPv6、静态、动态
Two independent choices. Switch each and read what it means.
两个相互独立的选项。切换每一个并阅读其含义。
Try it yourself
动手试试
Move to a new network
切换到新网络
A laptop has a MAC address and an IP address. Move it to a different network and see which one changes.
一台笔记本电脑同时拥有 MAC 地址和 IP 地址。把它切换到另一个网络,看看哪一个会改变。
Explainer · 3.4.4
讲解 · 3.4.4
The role of a router
路由器的作用
A router sits between a local network and the wider internet. Its roles:
路由器位于本地网络与更广阔的互联网之间。它的作用包括:
| Role | 作用 | What it means | 具体含义 |
|---|---|---|---|
| Sends data to a specific destination | 将数据发送到特定目的地 | it reads the address on each packet and forwards it to the right device, on the local network or out to the internet | 它读取每个数据包上的地址,并将其转发到正确的设备,可以是本地网络中的设备,也可以是转发到互联网 |
| Assigns IP addresses | 分配 IP 地址 | it gives each device that joins the local network its own IP address | 它为每台加入本地网络的设备分配各自的 IP 地址 |
| Connects a local network to the internet | 将本地网络连接到互联网 | it links the LAN to the internet so the devices on it can reach outside | 它将局域网连接到互联网,使网络中的设备能够访问外部 |
A router forwards data and connects networks. It does not store web pages, run programs, or convert analogue to digital. Keep the answer to the three roles above.
路由器负责转发数据和连接网络。它不存储网页、不运行程序,也不进行模数转换。答案应限于上述三项作用。
Try it yourself
动手试试
What a router does
路由器的作用演示
One local network, one router, the internet. Step through each of the router’s jobs.
一个本地网络、一台路由器、互联网。逐步查看路由器的每一项工作。
Check your understanding
检验你的理解
Which address is set at manufacture and identifies the physical network hardware?
哪种地址在生产时设定,并用于标识物理网络硬件?
Check your understanding
检验你的理解
What does the first half of a MAC address represent?
MAC 地址的前半部分代表什么?
Check your understanding
检验你的理解
Which of these is not a role of a router?
以下哪一项不是路由器的作用?
Common mistakes
常见错误
3.4.1 to 3.4.4
考官针对 3.4.1 至 3.4.4 报告了以下模式
RecurringAsked for the characteristics of a MAC address, candidates give its purpose instead (“it uniquely identifies a device”). Characteristics: written in hexadecimal, set at manufacture, made of a manufacturer code and a serial code.
反复出现被问及 MAC 地址的特征时,考生却给出了它的用途("它能唯一标识一台设备")。特征应为:以十六进制书写、生产时设定、由制造商代码加序列代码组成。
On IPv4 vs IPv6, few can state the differences. IPv4: 32 bits, four denary groups, dots. IPv6: 128 bits, eight hex groups, colons. Some give an advantage of IPv6 when the question asked for a characteristic or a difference.
在 IPv4 与 IPv6 的对比上,能说清区别的考生很少。IPv4:32 位、四组十进制数字、以点号分隔。IPv6:128 位、八组十六进制数字、以冒号分隔。有些考生在题目要求特征或区别时,却给出了 IPv6 的优点。
The NIC is wrongly said to be “allocated the IP address”. The NIC carries the MAC address; the network (its router) assigns the IP address.
NIC 常被错误地说成"被分配了 IP 地址"。NIC 携带的是 MAC 地址;分配 IP 地址的是网络(其路由器)。
Router answers drift into things a router does not do (storing pages, running software), or are too vague. Stick to: forwards data to a destination, assigns IP addresses, connects a LAN to the internet. Also be precise: “the sender’s IP address” and “the recipient’s IP address”, not just “IP address”.
关于路由器的答案常偏向路由器并不具备的功能(存储网页、运行软件),或过于笼统。应坚持只写:将数据转发到目的地、分配 IP 地址、将局域网连接到互联网。同时要精确:应写"发送方的 IP 地址"和"接收方的 IP 地址",而不是笼统地写"IP 地址"。
Purpose, not characteristic: “A characteristic of a MAC address is that it uniquely identifies a device on the network.”
说的是用途,不是特征:"MAC 地址的一个特征是它能唯一标识网络中的一台设备。"
Characteristics: “A MAC address is written in hexadecimal as six pairs of digits, is set when the NIC is manufactured, and is made of a manufacturer code followed by a serial code.”
说的是特征:"MAC 地址以十六进制书写,为六组数字对,在 NIC 生产时设定,由制造商代码加序列代码组成。"
Generic: “An IPv4 address is used to identify a device on the internet.”
过于笼统:"IPv4 地址用于标识互联网上的一台设备。"
IPv4-specific: “An IPv4 address is 32 bits long, written as four groups of denary numbers separated by full stops.”
IPv4 特有内容:"IPv4 地址长度为 32 位,写作四组十进制数字,以句点分隔。"
Revision questions
复习题
Past-paper style. Write an answer, then reveal the marking points and mark yourself.
采用历年真题风格。写下答案,然后展开评分要点给自己打分。
[2]State the purpose of a network interface card (NIC).
[2]陈述网络接口卡(NIC)的用途。
Marking points
评分要点
- The NIC provides the hardware a device needs to connect to / join a network.
- It also carries the device's MAC address.
- NIC 提供设备连接 / 加入网络所需的硬件。
- 它还携带设备的 MAC 地址。
[3]Describe three characteristics of a MAC address.
[3]描述 MAC 地址的三个特征。
Marking points
评分要点
- Any three: it is written in hexadecimal (six pairs of digits); it is set by the manufacturer / at manufacture and does not normally change; it is made of a manufacturer code followed by a serial code; it uniquely identifies that piece of hardware.
- 任选三点:以十六进制书写(六对数字);由制造商 / 在生产时设定,通常不改变;由制造商代码后接序列代码组成;唯一标识那一件硬件。
[4]Give two differences between an IPv4 address and an IPv6 address.
[4]说出 IPv4 地址与 IPv6 地址之间的两项区别。
Marking points
评分要点
- Any two: IPv4 is 32 bits, IPv6 is 128 bits; IPv4 is written as four denary groups separated by full stops, IPv6 as eight hexadecimal groups separated by colons; IPv6 provides far more possible addresses, which matters because IPv4 addresses are running out.
- 任选两点:IPv4 是 32 位,IPv6 是 128 位;IPv4 写作用句点分隔的四组十进制数,IPv6 写作用冒号分隔的八组十六进制数;IPv6 提供多得多的可用地址,这很重要,因为 IPv4 地址正在耗尽。
[2]Explain the difference between a static and a dynamic IP address.
[2]解释静态 IP 地址与动态 IP 地址之间的区别。
Marking points
评分要点
- A static IP address stays the same every time the device connects.
- A dynamic IP address is assigned (from a pool) when the device connects and can be different the next time.
- 静态 IP 地址在设备每次连接时都保持不变。
- 动态 IP 地址在设备连接时(从地址池中)分配,下次可能不同。
[3]Describe the role of a router in a home network.
[3]描述路由器在家庭网络中的作用。
Marking points
评分要点
- Any three: it forwards data packets between the local network and the internet, towards their destination; it connects the local network (LAN) to the internet; it assigns (dynamic) IP addresses to devices on the local network; it uses a routing table to choose the path.
- 任选三点:它在本地网络与互联网之间转发数据包,朝目的地转发;它把局域网(LAN)连接到互联网;它为本地网络上的设备分配(动态)IP 地址;它用路由表选择路径。
Flashcards
记忆卡片
Active recall for this subtopic’s key terms.
针对本子主题关键术语的主动回忆练习。
Keep this subtopic’s practice with you
把这个子主题的练习保存下来
Free account: unlock every revision question and flashcard for 3.4, and every other IGCSE 0478 statement.
免费账户:解锁 3.4 以及所有其他 IGCSE 0478 考纲陈述的全部复习题和记忆卡片。