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Computer Networks Explained: Devices, Data Exchange, and Basic Network Types

Learn what computer networks are, how devices exchange data, and how switches, routers, packets, protocols, LANs, Wi-Fi, Ethernet, DNS, and HTTP work together.

A computer network is a group of connected devices that exchange data and share resources. The devices may include computers, phones, servers, printers, routers, switches, and other connected equipment.

Networks make it possible to communicate, share files, use shared printers, access applications and services, and connect to the Internet. A home Wi-Fi network and a large business network use the same broad idea: connected devices follow communication rules to exchange information.

This lesson introduces the devices, connection methods, protocols, packets, and network types that form the foundation of networking.

What Is a Computer Network?

A computer network connects two or more devices so they can send and receive data. The connection may use a physical cable, such as Ethernet, or a wireless radio link, such as Wi-Fi.

A network can be very small. For example, two office computers connected to a switch form a small local network. A home network may include phones, laptops, a smart television, a printer, and a router. Large organizations can connect thousands of devices across many buildings.

Networks commonly provide these benefits:

Communication: People can exchange messages, email, voice, and video.
File sharing: Users and applications can access files stored on another computer or server.
Service access: Devices can use web applications, databases, cloud services, and other network services.
Printer sharing: Several computers can use one network printer.
Internet access: A local network can use a router and an Internet service connection to reach external networks.

Nodes, Endpoints, and Intermediary Devices

A node is a device or connection point that participates in a network. A node must have a way to send, receive, or help forward network data.

An endpoint is an end-user or end-service device that sends or receives data. Examples include a desktop computer, laptop, phone, tablet, network printer, server, or smart camera. Endpoints are usually the source or final destination of a communication.

An intermediary device helps move traffic between endpoints. A switch connects devices within a local network. A router forwards traffic between separate networks. Other networks may also contain wireless access points, firewalls, and service-provider equipment.

For example, when a laptop requests a web page, the laptop is an endpoint. A home router is an intermediary device. The web server that supplies the page is another endpoint, even though it may be located on a distant network.

How Devices Connect: Wired and Wireless Media

The connection medium carries signals between devices. A medium can be a physical cable or a wireless radio link.

Wired connections

Ethernet is a widely used wired LAN technology. Ethernet commonly uses twisted-pair cables with connectors designed for network equipment. A computer can connect to a switch or router through an Ethernet cable.

Wired connections are often useful when a stable, predictable connection is important. Offices, desktop computers, servers, game consoles, and network printers commonly use cables. A cable also avoids the radio interference and signal coverage concerns that can affect wireless connections.

Wireless connections

Wi-Fi is a wireless LAN technology. A phone or laptop uses a radio link to communicate with a wireless access point, often built into a home router. The access point then connects the wireless device to the rest of the LAN.

Wireless access is convenient because devices can move without a cable. Its performance depends on factors such as distance, obstacles, radio interference, and the capabilities of the devices. Wired and wireless devices can participate in the same LAN when the network equipment connects their traffic.

Common Components of a Simple Network

Component	Primary role	Typical example
Endpoint device	Sends or receives data for a user or service	Laptop, phone, server, or printer
Switch	Connects multiple devices within a local network	Small office Ethernet switch
Router	Forwards traffic between separate networks	Home router connecting a LAN to an Internet provider
Wired medium	Carries network signals through a physical cable	Ethernet cable
Wireless medium	Carries network signals over a radio link	Wi-Fi connection
Internet service	Provides a path from a local network to external networks	Service supplied by an Internet service provider

Protocols: Rules for Communication

Connected devices need agreed technical rules to communicate successfully. A protocol is a defined set of communication rules used by network devices and applications.

Protocols can specify how data is formatted, how devices are addressed, how data is transmitted, how a recipient confirms or processes a message, and how the meaning of the data is interpreted. Without shared rules, one device might send information in a form that another device cannot understand.

Internet protocols are standards that allow separate networks and devices around the world to communicate. They cover different tasks. DNS helps locate a service, while HTTP defines a common way for a browser and a web server to request and deliver web resources.

DNS

DNS, or the Domain Name System, helps map human-readable domain names to network addresses. People can remember a name such as example.com more easily than a numerical address. Before a browser contacts a site, it can ask a DNS service for the address associated with the name.

DNS does not deliver the complete web page. Its main job in this example is helping the client find the destination address.

HTTP and HTTPS

HTTP is a web protocol used by clients and web servers to request and transfer web resources. A browser acts as the client when it requests a page, image, or other resource from a web server.

HTTPS is the secure form of web communication commonly used today. It uses HTTP together with encryption and authentication protections. Both HTTP and HTTPS describe the web request and response at the application level; the network still needs addressing and forwarding mechanisms to move the data.

Packets and Data Transfer

Networked information is transmitted as formatted units called packets. A packet carries part of the information being exchanged. A packet generally includes payload data, which is the useful content, plus control information needed for delivery.

Control information can identify a source, a destination, or how the data should be handled. The exact format depends on the technology and protocol involved, so not every networking technology uses precisely the same packet structure.

Packets may pass through intermediary devices before reaching their destination. For example, a laptop may send packets to a home router. The router forwards suitable traffic to the service provider, and additional routers in other networks forward the packets toward a web server. The server sends response packets back through a path to the laptop.

Breaking information into packets allows network equipment to share communication links among many conversations. It also allows protocols to manage delivery as a sequence of smaller units rather than as one continuous block.

Local Area Networks

A Local Area Network, or LAN, is a network serving a limited physical area. A home, office, classroom, floor, or building may contain a LAN.

A typical home LAN includes phones and laptops connected by Wi-Fi, along with wired devices such as a desktop computer or printer. The devices can communicate locally when the relevant network settings and permissions allow it. For example, a laptop might send a document to a printer on the same home LAN.

A LAN can also connect to external networks. The home router provides the path from the local network to the Internet. Local communication and Internet communication are related but not identical: traffic between two devices in the same LAN may remain local, while traffic destined for another network must be forwarded by a router.

The Internet: A Network of Networks

The Internet is a global interconnection of many separate networks. It is not one small network controlled by a single switch. Home networks, school networks, business networks, data-center networks, and service-provider networks connect through routers and other infrastructure.

When a device in a home accesses an Internet service, the general path is:

The device connects to the home LAN through Wi-Fi or Ethernet.
The device sends traffic to the home router when the destination is outside the LAN.
The router forwards the traffic through the Internet service provider's infrastructure.
Additional networks and routers carry the traffic toward the remote service.
The remote service sends response traffic back toward the home network.

This arrangement allows independently operated networks to communicate while retaining their own local equipment and administration.

What Does a Router Do?

A router is a device that forwards traffic between separate networks. It examines information about a packet's destination and selects a path toward another network.

In a home, the router connects the LAN to the Internet service provider's network. It may also provide Wi-Fi, basic security functions, and other features, but those features are not the fundamental definition of routing. Routing means moving traffic between different networks.

Consider two computers in the same office LAN. Their traffic can be handled locally by the LAN equipment. If one computer requests a service on the Internet, the traffic must leave the office LAN through a router. The router is therefore the boundary device that provides a path to another network.

What Does a Switch Do?

A switch is a device that connects multiple devices within a local network. Each device can connect to a switch port, usually with an Ethernet cable. The switch provides local connectivity so the connected devices can exchange LAN traffic.

For example, two computers in a classroom can connect to a central switch. The switch provides the local connection between them. If the computers also need to reach a website, the LAN normally has an uplink to a router, which connects the LAN to another network.

Device	Main purpose	Where it is commonly used	What it connects
Switch	Provides connectivity within a local network	Office, classroom, lab, or data center	Multiple devices on the same LAN
Router	Forwards traffic between separate networks	Home, office, service-provider, or enterprise network	A LAN and another network, such as the Internet

A switch alone does not normally provide Internet access. It can connect local devices, but a router is needed to forward traffic from that LAN to an external network.

DNS, HTTP, and HTTPS in a Website Request

Protocol	Problem it solves	Simple example
DNS	Maps a human-readable domain name to a network address	Finding the address associated with a website name
HTTP	Defines requests and responses for web resources	A browser requests an HTML page from a web server
HTTPS	Provides protected web communication using HTTP with security mechanisms	A browser securely requests an account or shopping page

A Simple Network Communication Path

Suppose a user enters a domain name into a browser on a laptop.

Local connection: The laptop connects to the home LAN through Wi-Fi or Ethernet. The home router or wireless access point provides the local connection.
Name lookup: The device or its configured DNS service uses DNS to find a network address for the domain name.
Local forwarding: Because the web server is outside the home LAN, the laptop sends the traffic toward the home router.
Internet forwarding: The router sends packets through the service provider and other networks toward the web server.
Web request: The browser uses HTTP or HTTPS to request the web content.
Response: The web server returns response data. Packets travel back through external networks, the router, and the LAN to the laptop.
Display: The browser interprets the response and displays the page to the user.

DNS and HTTP or HTTPS have different jobs. DNS helps find the destination. HTTP or HTTPS describes the web exchange. Switches and routers move traffic through local and external networks. The laptop and web server are endpoints.

Switches, Routers, and Local Versus External Traffic

It is useful to ask whether the destination is local or belongs to another network.

Local traffic: Two computers in the same LAN may communicate through the LAN's switching equipment.
External traffic: Traffic for a server on another network must be sent to a router so it can be forwarded beyond the LAN.

In a home device, the router, switch, and Wi-Fi access point may be combined in one consumer box. Their functions are still conceptually different: switching connects local devices, wireless access provides a radio connection, and routing forwards traffic between networks.

An Introduction to Layered Networking

Networking tasks are organized into layers so that each part of communication has a clear responsibility. One layer may handle an application's request, another may handle addressing and routing, and another may handle delivery over Ethernet or Wi-Fi.

The OSI reference model is a conceptual layered model for understanding network communication functions. It helps students describe where a technology or problem belongs. For example, an application protocol such as HTTP has a different responsibility from a physical connection such as an Ethernet cable.

Protocols and devices can be associated with different layers, although real-world products often combine several functions. This lesson uses layers only as an introduction; detailed OSI-layer behavior and the TCP/IP model are separate topics.

Troubleshooting Basic Network Problems

Connected to Wi-Fi but websites do not open

A device can have local LAN connectivity without having working Internet access. The wireless link may be working while the router's upstream connection or the service provider's network is unavailable.

DNS may also be the problem. If DNS cannot resolve a domain name, the device may be unable to find the website even when some network path still exists. This symptom requires distinguishing between Wi-Fi connectivity, router connectivity, Internet connectivity, and name resolution.

Two wired office computers cannot communicate

Check whether both computers have functional Ethernet connections and are connected to the intended switch. Faulty cables, disabled network interfaces, or incorrect network configuration can prevent communication. The switch is the usual local connectivity device for multiple wired computers.

Expecting a switch to provide Internet access

A switch connects devices on a LAN, but it does not replace the router's role of connecting that LAN to another network. A small office typically needs a switch for local wired connections and a router or gateway for Internet connectivity.

Key Terms to Remember

Computer network: A group of connected devices that exchange data and share resources.
Node: A device or connection point participating in a network.
Endpoint: An end-user or end-service device that sends or receives network data.
Intermediary device: Equipment that helps move traffic between endpoints, such as a switch or router.
LAN: A Local Area Network serving a limited physical area.
Internet: A global interconnection of many separate networks.
Packet: A formatted unit of data transmitted across a network.
Protocol: A defined set of communication rules used by network devices and applications.
Ethernet: A widely used wired LAN technology.
Wi-Fi: A wireless LAN technology.
DNS: A naming system that helps map domain names to network addresses.
HTTP: A web protocol used to request and transfer web resources.
Router: A device that forwards traffic between separate networks.
Switch: A device that connects multiple devices within a local network.
OSI reference model: A conceptual layered model for understanding network communication functions.

Summary

A computer network connects devices so they can exchange data and share resources. Endpoints generate or receive data, while intermediary devices help deliver it. Ethernet provides wired connectivity, and Wi-Fi provides wireless LAN connectivity.

Protocols provide the rules for communication. Packets carry formatted pieces of information through switches, routers, and other network equipment. A LAN serves a limited area, while the Internet connects many independent networks. DNS helps locate a service, and HTTP or HTTPS supports web requests and responses.

These concepts provide the foundation for studying computer networking, IP addressing, switching, routing, wireless networking, and network troubleshooting.