5 - Fundamentals of Computer Networks

Question 1

Network

Answer 1

An interconnection of computers and other pieces of hardware to facilitate communication and the sharing of resources

Question 2

Network adv and dis

Answer 2

Adv:

• Resources such as printers, internet connections and files can be shared, saving both money and effort
• Communication can take place via email or instant messaging
• Backing up data to a different computer is far more straightforward

Dis:

• Management of a network is a specialist skill, which can be quite expensive
• Security procedures are needed to prevent unauthorised access to a potentially large number of computers
• Network hardware, including cables and switches, can be expensive

Question 3

PAN

Answer 3

Personal Area Network

This describes devices owned by a single user, connected via Bluetooth, such as a phone, tablet and headset

Question 4

LAN

Answer 4

Local Area Network
This is a network covering a single building or perhaps a campus. Usually, a single organisation owns all hardware that belongs to a LAN

Question 5

WAN

Answer 5

Wide Area Network
This would be spread over a large geographical area, with shared ownership of some hardware (a telecommunications company might own much of the cabling). The Internet is the largest example of a WAN

Question 6

Wired Vs Wireless

Answer 6

Wired:

• More secure, as physical connection is needed, so a hacker would need to be in the building
• Less prone to interference

Wireless:

• Much easier to add a device
• No requirement to stay in the same place

Question 7

Connection Media: Wireless

Answer 7

Radio Waves

Question 8

Connection Media: Wired

Answer 8

Optical fibre
Can be used for very fast connections, or if lots of computers are going to share a single connection

Copper cabling
Cheaper and slower, although it is quick enough for most activities that a single computer would perform online

Question 9

Network Topology

Answer 9

The pattern in which the hardware on a network is positioned, including connections. Common topologies include star and bus

Question 10

Topology: Star

Answer 10

Every device is connected to a switch at the centre of the network. All communication travels via this switch

Adv:

• Very few data collisions, since each device has a dedicated line to the switch
• Strong, centralised security

Dis:

• Lost of cabling needed
• If the switch has no spare ports, adding another device can be difficult

Question 11

Topology: Bus

Answer 11

A central cable called the backbone, running between two terminators, connects all devices

Adv:

• Uses relatively little cable, making it quite inexpensive
• Additional devices can be easily added

Dis:

• Collisions can occur, as multiple transmissions will attempt to use the shared backbone
• If a large number of devices are connected, network transmission can be slow (due to collisions)

Question 12

Protocol

Answer 12

A set of rules that governs how a computer communicates on a network. Computers have many protocols, each necessary for a different purpose (email, accessing web pages, moving files, etc.). Without protocols, communication between computers would be impossible

Question 13

Protocol: Ethernet

Answer 13

A family of protocols rather than a single protocol

This is a set of rules that governs how data is formatted for transmission across a LAN

Question 14

Protocol: Wi-Fi

Answer 14

Letters aren’t short for anything, but are a brand name

These rules control how data is transmitted on WLAN

Question 15

Protocol: TCP/IP

Answer 15

Transfer Control Protocol and Internet Protocol
These are 2 protocols that often work together
Their collective roles is to break up data into packets, each of which is a chunk of data that knows where it has been sent from and where it is to be delivered to

Question 16

Protocol: UDP

Answer 16

User datagram protocol
Transmits data packets very quickly, but without checking to see whether each packet has arrived, so is not always reliable

Question 17

Protocol: HTTP

Answer 17

Hyper text transfer protocol
This is the set of rules governing how hypertext (language of the WWW) is moved around the Internet, from device to device

Question 18

Protocol: HTTPS

Answer 18

HTTP Secure
This encrypts data that is sent across the internet. Encrypted data cannot be read if intercepted, so is favoured when sending passwords or credit card numbers

Question 19

Protocol: FTP

Answer 19

File transfer protocol
This is how files are moved from 1 computer to another across the internet. This protocol is heavily relied upon in building websites, moving files from the dev’s comp to a server, from where they can be accessed publicly

Question 20

Protocol: SMTP

Answer 20

Simple mail transfer protocol

While POP3 might be used to retrieve emails, SMTP is used to send them from one server to another

Question 21

Protocol: IMAP

Answer 21

Internet message access protocol

This email protocol is used to allow multiple devices (laptops, tablets, phones, etc.) to access the same email account

Question 22

Internet protocol address

Answer 22

A unique number used to identify every device connected to the internet. No 2 IP addresses are the same. If your computer requests a web page, your computer’s IP address specifies where that web page should ultimately be delivered

Question 23

Authentication

Answer 23

Measures to make sure that a person trying to access data is who they say they are. This can take place by way of:

• Usernames and passwords
• Memorable info, such as mother’s maiden name
• Checking that they are using a recognised IP address

Question 24

Encryption

Answer 24

Scrambling data using a key to ensure that is makes no sense to anyone who intercepts it. When it is received, the recipient also has a key which can be used to decrypt the data, returning it to its readable form

Question 25

Firewalls

Answer 25

These can be either hardware, software or both. A firewall can be told to block certain traffic (such as all emails or any traffic from a suspect IP address) or to only allow certain traffic (such as from a single, trusted device), blocking everything else

Question 26

MAC address filtering

Answer 26

Each computer has a MAC (Media Access Control) address which, unlike an IP address, cannot be changed. Based on this unique identifier, specific devices can be either permitted onto, or blocked from, a network

Question 27

TCP/IP model

Answer 27

A series of protocols. When they work together, they transmit data from one computer, through any number of pieces of network hardware, to another computer. The TCP/IP model is a concept, not a physical thing

The model has 4 layers, each containing a n.o of protocols. When data is sent, protocols at 1 layer break down and repackage the data into smaller unity, before passing the data to the layer below. When data is received, those units are reassembled as they move up the model

Question 28

Application Layer

Answer 28

Where network apps, including browsers and email apps, operate

Protocols: HTTP, HTTPS, FTP, SMTP, IMAP

Question 29

Transport Layer

Answer 29

Establishes comms between the sender and the recipient, agreeing on how comms will take place

Protocols: TCP, UDP

Question 30

Network Layer

Answer 30

Packages data for transmission by breaking it into units called packets, which are sent across the network

Protocols: IP

Question 31

Network Interface Layer

Answer 31

The physical components of the computer, such as the NIC, operate at this level

Protocols: Ethernet, Wi-Fi