The Internet
Introduced| English |
|---|
| Internet/ˈɪntənet/ |
| protocols/ˈprəʊtəkɒlz/ |
| packets/ˈpækɪts/ |
| IP address/ˌaɪ ˈpiː əˈdres/ |
| World Wide Web/wɜːld waɪd web/ |
| redundancy/rɪˈdʌndənsi/ |
A network of networks
- The Internet 互联网 is a network of interconnected networks — millions of smaller ones joined into one global system.
- What lets so many different machines cooperate is a shared set of rules called protocols 协议.
- A protocol is simply an agreed set of rules for how systems format and exchange data.
- So a phone from one company can talk to a server built by another.
The Internet is:
Millions of smaller networks joined into one global system.
An agreed set of rules for how systems exchange data is a ______.
Protocols let different machines cooperate.
Data travels as packets
- Data does not travel as one big block — it is chopped into small packets 数据包.
- Each packet carries a piece of the message plus address information.
- Packets travel independently, possibly by different routes, and are reassembled in order on arrival.
- To find their destination, they use the IP address 网际协议地址 — a unique number for each device.
How a message travels as packets
A message is split into packets, each addressed and numbered, routed independently across the network, then reassembled in order at the destination.
Data is sent across the Internet as:
Packets take possibly different routes and are reassembled in order.
An IP address is:
Like a postal address, it tells packets where to go.
Internet vs the Web
- Two terms are often confused.
- The Internet is the physical network of cables, routers, and machines.
- The World Wide Web 万维网 is just one service running on top of it — linked web pages you open in a browser.
- Email and video calls are other services that also use the Internet.
The World Wide Web is:
The Internet is the network; the Web is one service on it.
Redundancy means there is usually more than one path between two points, so a failed link can be bypassed.
Multiple paths are why the Internet keeps working when parts fail.
Redundancy
- A key strength is redundancy 冗余: usually more than one path between any two points.
- If one cable or router fails, packets simply travel another way and still arrive.
Sending a photo. The file splits into ~20 packets, each stamped with your friend's IP address and a sequence number. Packet 5 might go through Tokyo while packet 6 goes through Singapore — yet both arrive, and the sequence numbers rebuild the photo in order. No single cable carried the whole photo.
The Internet is a network of networks that cooperate through shared protocols. Data travels as independent packets, each addressed by an IP address and reassembled in order. The World Wide Web is just one service on top of it. Redundancy — many possible paths — keeps data flowing when a link fails.