2.1 Networks including the internet: Hardware Supporting the Internet

This section describes the key hardware components that enable the internet to function. These components work together to transmit data across vast distances, from our devices to servers and back.

1. Network Interface Cards (NICs)

A Network Interface Card (NIC), also known as a network adapter, is a hardware component that connects a computer to a network. It allows the computer to communicate with other devices on the network.

• Ethernet NICs: These are the most common type of NIC, using Ethernet cables (e.g., Cat5e, Cat6) to connect to a network.
• Wireless NICs: These allow a device to connect to a network wirelessly, typically using Wi-Fi technology.

2. Routers

A router is a network device that forwards data packets between computer networks. It plays a crucial role in directing traffic on the internet.

Routers examine the destination IP address of incoming packets and determine the best path to forward them. They often connect a home or office network to the internet service provider (ISP).

Feature	Description
Function	Forwards data packets between networks.
IP Addressing	Uses IP addresses to determine routing paths.
Network Address Translation (NAT)	Allows multiple devices to share a single public IP address.

3. Modems

A modem (modulator-demodulator) converts digital signals from a computer into analog signals suitable for transmission over telephone lines or cable networks, and vice versa.

Historically, modems were essential for dial-up internet access. Modern modems are often integrated into routers and are used for broadband connections (e.g., cable modems, DSL modems).

1. DSL Modems: Used with Digital Subscriber Line (DSL) technology, which transmits data over existing telephone lines.
2. Cable Modems: Used with cable internet service, which transmits data over coaxial cables.

4. Switches

A switch connects multiple devices on a local area network (LAN). It allows devices to communicate with each other efficiently.

Switches learn the MAC addresses of devices connected to them and forward data only to the intended recipient, improving network performance.

5. Hubs

A hub is a simpler networking device that connects multiple devices on a LAN. It operates by broadcasting data to all connected devices.

Hubs are less efficient than switches because they do not filter traffic, leading to potential network congestion. They are largely obsolete now.

6. Servers

Servers are powerful computers that provide resources and services to other devices on a network. They are essential for the operation of the internet.

Types of servers include:

• Web Servers: Host websites and deliver web pages to users.
• File Servers: Store and manage files that can be accessed by users on the network.
• Database Servers: Store and manage databases.
• Mail Servers: Handle email communication.

7. Transmission Media

Transmission media are the physical pathways that carry data signals. Different types of media are used to connect devices on the internet.

Media Type	Description	Advantages	Disadvantages
Copper Cable (e.g., Ethernet)	Uses copper wires to transmit data.	Relatively inexpensive, easy to install.	Susceptible to interference, limited bandwidth.
Fiber Optic Cable	Uses light to transmit data through glass or plastic fibers.	High bandwidth, immune to interference.	More expensive, more difficult to install.
Wireless (e.g., Wi-Fi)	Uses radio waves to transmit data.	Convenient, flexible.	Susceptible to interference, security concerns.

8. Satellites

Satellites are used to transmit data over long distances, particularly for internet access in remote areas.

A satellite dish on the ground communicates with a satellite orbiting the Earth, which then relays the data to a ground station.