How Computers Talk Across a Network
Computers communicate by breaking information into packets and sending those packets through a series of network layers and devices.
What Is a Protocol?
A protocol is a set of rules that devices follow when communicating. Without common rules, computers would not know how to format, send or interpret information.
HTTP and HTTPS
Used to request and deliver web pages and web content.
TCP
Provides reliable delivery and checks that data arrives correctly.
UDP
Provides fast communication without the same delivery guarantees.
Ethernet
Defines how devices communicate across wired local networks.
Data Is Sent as Packets
A large file or message is divided into smaller pieces called packets. Each packet contains information such as its source, destination and position within the original message.
- The application creates data.
- Protocols add headers containing addressing and control information.
- The data is divided into packets.
- Routers and switches forward the packets.
- The receiving device reassembles the packets.
TCP/IP Layers
| Layer | Function | Examples |
|---|---|---|
| Application | Provides network services to applications. | HTTP, DNS, SMTP |
| Transport | Controls conversations and delivery. | TCP, UDP, ports |
| Internet | Provides logical addressing and routing. | IP, ICMP |
| Network Access | Moves data across the physical network. | Ethernet, Wi-Fi, fibre |
Ports Identify Services
An IP address identifies a device. A port number identifies a service or application running on that device.
HTTPS: 443
HTTP: 80
DNS: 53
SSH: 22
FTP: 21Think of it this way: Think of an IP address as a building address and a port as a room number. Together, they help data reach the correct service.
TCP and UDP
TCP checks that packets arrive and can retransmit missing information. UDP is faster and is often used for live video, voice calls, gaming and other applications where speed is more important than perfect delivery.
Summary
Computers communicate through protocols. Data is divided into packets, labelled with addresses and ports, transported through network devices, and rebuilt by the receiving computer.
