A network is formed when computers and other devices are connected so that they can communicate and share resources such as printers, files and software. Networks can range from a few devices in one building to the internet, which is the largest network.
Click a subtopic and the page will automatically scroll to that part of the chapter.
A Network Interface Card (NIC) allows a computer or other device to connect to a network.
A MAC (Media Access Control) address is a unique address given to a network device when it is manufactured. It identifies the physical device on a network.
It is often called the physical address.
An IP (Internet Protocol) address identifies the location of a device on a network. It is usually assigned when the device connects to a network or the internet. Unlike a MAC address, an IP address may change when the device connects from a different location.
IPv6 was introduced because of the huge growth in the number of devices connected to the internet.
| MAC address | IP address |
|---|---|
| Identifies the physical device | Identifies a device/location on a network |
| Linked to the NIC | Assigned when connecting to a network |
| Normally remains unchanged | Can change |
| Used by switches | Used by routers |
Data sent across a network is divided into smaller pieces called data packets.
The sequence number allows the receiving computer to put all the packets back into the correct order.
Packets may travel through several routers before arriving at their destination.
A hub connects devices together in a LAN. When a hub receives a data packet, it sends the packet to every device connected to it.
A switch also connects devices together in a LAN, but it works more intelligently than a hub.
A switch stores the MAC addresses of connected devices in a look-up table. When a packet arrives, the switch checks the MAC address and sends the packet only to the intended device.
| Hub | Switch |
|---|---|
| Connects devices in a LAN | Connects devices in a LAN |
| Sends data to every device | Sends data only to the correct device |
| Wastes bandwidth | Uses bandwidth more efficiently |
| Less secure | More secure |
| Does not use a MAC look-up table | Uses MAC addresses and a look-up table |
A bridge connects two LANs, or two parts of a LAN, that use the same communication protocol.
A router transfers data packets from one network to another. Routers use IP addresses to decide where packets should be sent.
A common use is connecting a LAN to the internet. A router stores a routing table, which helps it decide the next route a packet should take.
When the packet reaches the destination network:
| Router | Bridge |
|---|---|
| Connects different networks | Mainly connects LANs |
| Uses IP addresses | Uses MAC addresses |
| Uses a routing table | Does not use a routing table |
| Can connect a LAN to external networks | Connects networks using the same protocol |
Both Wi-Fi and Bluetooth allow wireless communication using electromagnetic radiation.
Bluetooth is designed mainly for devices that are close together.
Bluetooth is useful when:
Wi-Fi is more suitable for full computer networks.
A Wi-Fi device connects through an access point (AP) or hotspot.
| Bluetooth | Wi-Fi |
|---|---|
| Shorter range | Longer range |
| Slower | Faster |
| Mainly connects nearby devices | Mainly used for networking/internet |
| Suitable for low-bandwidth uses | Suitable for much greater data transfer |
Cloud storage means storing data on remote servers rather than only on the user's own computer.
The same data may be stored on several servers so that it remains available if one server fails. This is called data redundancy.
The chapter identifies:
These are covered in greater depth later in the book, so detailed notes on them are not needed here.
A Local Area Network (LAN) connects computers and devices that are geographically close together, usually within one building or site.
A Wireless Local Area Network (WLAN) performs a similar role to a LAN but uses wireless communication instead of cables. Devices communicate through access points (APs).
Several APs may be needed in large locations such as airports or college campuses because wireless signals have a limited range.
| Wired | Wireless |
|---|---|
| Uses cables | Uses radio signals |
| Usually faster | Usually slower |
| More stable | Can suffer interference |
| More secure | Signals are easier to intercept |
| Devices have less mobility | Devices can move within range |
| Cables can create hazards | No network cables needed |
A Wide Area Network (WAN) connects computers or networks over a large geographical area.
Several LANs can be connected through routers to form a WAN.
| LAN | WAN |
|---|---|
| Small geographical area | Large geographical area |
| Often one building/site | Can cover cities or countries |
| Usually owned/managed locally | Often uses external communication networks |
| Generally easier to manage | More complex |
This part of the chapter focuses mainly on network security, authentication, anti-malware and electronic conferencing.
Passwords are commonly used to protect:
A password should be difficult for another person to guess.
A strong password should contain a mixture such as:
Passwords should also be changed regularly and protected against spyware.
Authentication is a method of proving a user's identity.
Zero login allows a user to access a system without manually entering a password.
It can identify a user using:
Physical characteristics such as:
Examples include:
A magnetic stripe card stores information magnetically on a stripe. The card is swiped through a reader. The stored information can then be compared with information in a database before access is allowed.
A smart card contains a chip and antenna.
Information such as:
can be stored on the card. A reader can detect the card and the user may then be asked to enter a PIN before access is granted.
A physical token is a hardware device used for authentication. It can generate a one-time password (OTP) that is valid for only a short period.
This gives stronger security because several pieces of authentication information are required.
An electronic token is software, often installed as an app on a smartphone. The app generates a temporary one-time password (OTP).
The user normally combines this with another authentication method such as:
| Physical token | Electronic token |
|---|---|
| Separate hardware device | Software/app |
| Generates an OTP | Generates an OTP |
| Must be carried by the user | Usually runs on a smartphone |
| Used for secure authentication | Used for secure authentication |
Anti-virus software protects a computer from viruses.
It can:
This means looking for behaviour that suggests a program may contain a virus, even if that exact virus is not yet in the antivirus database.
A suspicious file is isolated so that it cannot damage the rest of the system.
The chapter covers three types:
Video conferencing allows people in different locations to communicate using live video and sound.
It operates in real time over a network.
Important software includes:
Audio conferencing allows several people to communicate using sound only.
It can use:
VoIP (Voice over Internet Protocol) allows voice communication over the internet.
A weakness is that sound quality depends heavily on a fast and stable internet connection. Poor connections can cause:
A web conference uses the internet to hold a meeting in real time.
Participants usually join through a website or application.
| LAN | WLAN |
|---|---|
| Local network | Wireless local network |
| Usually uses cables | Uses wireless signals |
| Building/site | Building/site |
Students should be able to: