1.3- Computer networks, connections and protocols

Question 1

What is a network?

Answer 1

A computer network is a system of interconnected devices (e.g. computers, servers, printers, smartphones) that communicate with each other using transmission media and protocols.

Question 2

What are some uses of networks?

Answer 2

File sharing – Users can access and work on the same files from different devices.

Resource sharing – Hardware (like printers or scanners) can be shared across devices, reducing cost.

Communication – Users can send messages via email, video call, or instant messaging.

Centralised management – Admins can install updates, manage security, and monitor activity across all devices.

Remote access – Users can log into systems and access resources from anywhere via internet-based services (e.g. cloud storage).

Question 3

What are the disadvantages to networks?

Answer 3

There is an increased security risk to data

Malicious software can infiltrate the network and render it unusable

Servers and switches can provide a central point of failure, resulting in users not being able to complete tasks using their computer

Factors can impact the performance of the network such as the number of users and data on the network at one time

Question 4

What is a LAN?

Answer 4

LAN (Local Area Network):

Covers a small geographical area, like a school, home, or office.

Owned and maintained by the organisation using it.

Common hardware: switches, WAPs, and routers.

Offers high-speed, low-cost communication.

Question 5

What is a WAN?

Answer 5

WAN (Wide Area Network):

Covers a large geographical area, potentially global.

Uses third-party infrastructure (e.g. telecom lines, satellites).

The Internet is the largest WAN.

Usually slower and more expensive than LANs.

Question 6

How does bandwidth impact network performance?

Answer 6

Bandwidth is the amount of data that can be sent and received at any given time

Measured in bits per second (bit rate)

A smaller bandwidth means that less data can be sent and the network can slow down, potentially to the point of becoming unusable

Question 7

How does the number of users impact network performance?

Answer 7

This is how many users are on the network at the same time
Too many users can cause the network to slow down if there is not enough bandwidth for all of the data being sent and received

Question 8

How does latency impact network performance?

Answer 8

Latency is the delay between data being sent and received
If there is a big delay between the two, more data will be on the network causing collisions
This can lead to even more packets of data being sent as the error rate has increased

Question 9

How does the error rate impact network performance?

Answer 9

Error rate is the measure of how many packets of data do not reach their destination
An increased error rate occurs in less reliable connections - a poor wireless signal would be a contributing factor to an increased error rate

Question 10

How does the type of transmission media impact network performance?

Answer 10

Transmission media is the type of cable used in wired connections

Wired connections offer a higher bandwidth than wireless connections

The main options for transmission media are unshielded twisted pair and fibre-optic

Fibre optic has a higher bandwidth than copper cabling as well as faster transfer speeds

Question 11

What is a network model?

Answer 11

A network model is the logical structure of the network
It defines how the network will operate on top of the physical network structure (Star or Mesh)

Question 12

What is a client server model?

Answer 12

a client computer requests information or services from a server computer. The server then processes the request and sends back a response or the requested data.

The server is a powerful computer which provides services or resources required by any of the clients

A client is a computer or device which requests the services or resources provided by the server

Question 13

Advantages to the client-server model?

Answer 13

Managing backups of the network is easier as it is done from one central point

Updating and installing new software can be done centrally instead of having to log on to each machine

Security of files can be managed easily

Question 14

Disadvantages to the client server model?

Answer 14

Servers can be expensive to purchase, setup and maintain

A specialist network manager would be required as servers require specialist IT knowledge

Servers can be a single point of failure, meaning all users would lose access to the network if the server fails

Question 15

What is a peer to peer model?

Answer 15

all computers on the network are equal and can share resources and information directly with each other without a central server.

Question 16

Advantages of a peer to peer model?

Answer 16

Very easy to set up and maintain

Very cheap to set up because there is no expensive hardware to purchase

No specialist knowledge or staff are required to run the network

Question 17

Disadvantages of a peer to peer model?

Answer 17

Users will need to manage their own backups

Users will need to manage their own software updates

The network can be less secure

Question 18

What is a router?

Answer 18

The router is responsible for routing data packets between different networks.

The router can manage and prioritise data traffic, which can help to keep connections stable

The router will assign IP addressed to the devices on the network

Question 19

What is a wireless access point?

Answer 19

The Wireless Access Point (WAP) allows wireless devices to connect to a local area network (LAN)

The WAP connects to a Switch or Hub via an Ethernet cable

Question 20

What is a switch?

Answer 20

A Switch allows multiple wired devices to connect to a local area network (LAN)

The Switch is an active device, which means it can inspect network data and route it to the correct device, thus reducing traffic on the network. Hubs, by comparison will send the data to all connected computers

They know the MAC address of all connected computers and devices

Question 21

What is a network interface card?

Answer 21

The Network Interface Card (NIC) is required for a computer to connect to a network
A NIC can be both wired and wireless and allows your computer to send and receive data over a network

Question 22

What is transmission media?

Answer 22

Transmission media is the phrase used to describe the method of connecting a wired network

Question 23

What is a UTP connection?

Answer 23

Unshielded Twisted Pair (UTP)

A Twisted Pair cable is made up of insulated pairs of copper wires twisted around each other

Twister Pair is Low Bandwidth and more affordable than the other two cables, so is commonly found in Local Area Networks (LAN)

Question 24

What is fibre optic cable?

Answer 24

Use light signals to transmit data.

Question 25

What are the advantages and disadvantages of copper cable?

Answer 25

Advantages: tried and trusted technology relatively inexpensive Disadvantages: signal affected by electric and magnetic fields low bandwidth heavy cables

Question 26

What are the advantages and disadvantages of fibre optic cable?

Answer 26

Advantages: very fast data transmission low loss of signal over distance not affected by magnetic or electric fields require very little power more difficult to ‘tap into’ than copper cables Disadvantages: high investment cost need for expensive optical transmitters and receivers

Question 27

What are the advantages and disadvantages of wireless connections?

Answer 27

Advantages: no need for trailing wires (safer) allows devices to be used anywhere provided there is a signal Disadvantages: data transmission rate less than wired systems signal can be blocked by objects or walls increased security issues

Question 28

What is the Internet?

Answer 28

The Internet is a collection of networks spanning the whole world The Internet is the most well-known Wide Area Network (WAN) The Internet is used to provide connectivity

Question 29

How does the Internet work?

Answer 29

In your home, you have a router Inside your router is a modem which allows you to connect to your Internet Service Provider (ISP) via a telephone line or fibre optic An ISP is connected to a database called a Domain Name System (DNS) This results in other routers also connecting together, forming a large interconnection of multiple networks: Servers Other routers Other LANs All of these inter-connected networks are known as The Internet

Question 30

What is packet switching?

Answer 30

Unlike circuit switching where the whole message is sent in one go, with packet switching the message is broken down into smaller parts (data packets of 512 bytes) and these parts are sent individually through the network. The packets will travel across the network, usually in different directions, taking the shortest route available. When the individual packets arrive at their destination they will be reassembled back together in the correct order. Once all of the packets have safely arrived a message will be sent to the original computer as confirmation. If a packet is missing or corrupted then the message will instead be sent asking for that particular packet to be resent.

Question 31

What is each packet given in packet switching?

Answer 31

The IP address it is going to The IP address it has come from The sequence number of the packet The number of packets in the whole communication Error checking data

Question 32

What is a domain name system?

Answer 32

a crucial part of the internet that translates human-readable domain names (like "www.bbc.co.uk") into the numeric IP addresses that computers use to communicate.

Question 33

How does the domain name system work?

Answer 33

Step 1: User Enters a URL You type a website address (e.g. www.bbc.co.uk) into your web browser. This is called a Uniform Resource Locator (URL), which is a human-readable address. Step 2: DNS Query Begins Your computer sends a DNS query to a DNS Resolver (usually managed by your Internet Service Provider - ISP). The purpose is to find the IP address linked to the domain name. Step 3: Check the DNS Cache The DNS Resolver first checks its cache (memory) to see if it already knows the IP address for the domain. If it finds the address, it returns it straight away = faster browsing. If not, it starts the DNS lookup process. Step 4: Query the Root DNS Server The resolver sends a query to a Root DNS Server. The Root Server doesn’t know the final IP address, but it knows where to find it. It replies with the address of a Top-Level Domain (TLD) DNS server (e.g. for .com, .org, .uk). Step 5: Query the TLD Server The resolver then queries the TLD server based on the URL extension. The TLD server responds with the IP address of the Authoritative DNS Server for that domain (the server that holds the actual IP address of the website). Step 6: Query the Authoritative DNS Server The resolver sends a final query to the Authoritative DNS Server. This server returns the exact IP address for the requested website (e.g. 151.101.0.81). Step 7: IP Address Returned to Browser The DNS resolver returns the IP address to your web browser. This IP address is also stored (cached) by the resolver for future requests. Step 8: HTTP/HTTPS Request Sent Now your browser sends an HTTP or HTTPS request to the server at the given IP address. This request is asking for the web page content (HTML, CSS, images, etc.). Step 9: Server Sends Back Web Page The server responds by sending back the data needed to display the website. This includes HTML (structure), CSS (style), and JavaScript (interactivity). Step 10: Browser Renders the Web Page Your browser takes all this data and renders the website on your screen. This is the point where the full webpage is visible and interactive to the user.

Question 34

What are web servers?

Answer 34

Web servers are dedicated servers that store web pages/websites and other resources They have a dedicated IP address to ensure that users can access them 24/7

Question 35

What are clients?

Answer 35

Clients are end-users who make requests of web servers

Question 36

What is hosting?

Answer 36

Hosting is the storing of websites, files and other content on servers The servers need to be accessible by potentially thousands of users and they need to be available 24/7 The servers must be reliable and secure from any form of attack The IP address for the server must remain the same so that users can access the website whenever they want Servers are set up with the single purpose of serving these files in this manner and in a safe and secure way

Question 37

What is the cloud?

Answer 37

The cloud is a collection of servers which are used to store data, applications and files over the internet

Question 38

Advantages and Disadvantages of the cloud?

Answer 38

Advantages: Content in the cloud can be accessed anytime and from anywhere Users can use any device to access their content Users have a large storage capacity available to them Low cost / free to set up and use Users can easily collaborate Disadvantages: Accessing content and software is only possible when the user has an internet connection Expanding capacity can become expensive if using it across a business Vulnerable to security threats such as data leaks and photo leaks It is not thoroughly clear to users who is the owner of the data once it is uploaded to a cloud service Responsibility for backups and security is with the cloud service provider

Question 39

What is a star topology?

Answer 39

A star topology has a central switch which all other devices connect to. A star topology is commonly seen in most homes, businesses, organisations and schools

Question 40

Advantages of a star topology?

Answer 40

If any single cable stops working, the rest of the network will continue to work This is important because in other topologies if a cable was broken, all computers on the network would stop working which would have a negative impact on learning in schools and businesses completing their daily tasks Fast data transfer to the hub as each wire isn’t shared with other computers

Question 41

What are disadvantages of a star topology?

Answer 41

The central switch is a single point of failure This means that if the switch stops working, all of the devices connected to it will not be able to connect to the network or any of its facilities and resources Requires additional hardware such as the central switch and network cables

Question 42

What is a mesh topology?

Answer 42

A mesh topology allows all computers to be connected to all other computers This is known as a full mesh network topology

Question 43

What are the advantages of a full mesh topology?

Answer 43

If any single cable stops working, the rest of the network will continue to work as the data can find a different route to get to its destination Expansion and modification can be done without disrupting the network Data can be transmitted from different devices simultaneously

Question 44

What are the disadvantages to a full mesh topology?

Answer 44

The topology requires a lot of hardware, cables and switches to set up This means there is a higher cost for setting up the network Adding new devices is not as easy as in a star topology, making it more challenging to scale the network The solution to these disadvantages is called a ‘Partial Mesh Topology’ Can involve redundant connections Expensive to install cabling if using wired connections Network maintenance and administration is difficult

Question 45

What is a partial mesh topology?

Answer 45

A partial mesh topology is very similar to a full mesh, with the difference being that each device is not connected to every other device directly

Question 46

What are the advantages to a partial mesh topology?

Answer 46

Less cables and hardware are required Multiple routes still exist between devices It is a compromise solution to reduce the amount of hardware needed

Question 47

What is a wired network?

Answer 47

A wired network is a network where physical cables are used to join devices together and transmit data Computers can be connected to networks using many different types of wires to transmit data The most common type of cable in a local area network (LAN) is Ethernet

Question 48

What is ethernet?

Answer 48

Ethernet is a wired networking standard to carry electrical signals between devices. Ethernet uses twisted pair cables to allow duplex communication. It describes how devices should format data ready for transmission between computers on the same network

Question 49

Advantages of ethernet?

Answer 49

Speed - Fast data transfer Security - Better physical security Range - High (up to 100m), less susceptible to interference

Question 50

Disadvantages of ethernet?

Answer 50

Portability - Can't move easily, location is limited by physical cable Cost - Need more cables to add a new device Safety - Cables can be trip hazards, need routing along walls, under floors

Question 51

What is a wireless network?

Answer 51

A wireless network is a network where connections are made using radio waves to transmit data through the air

Question 52

What are the most common types of wireless network?

Answer 52

The most common types of wireless connections are: Wi-Fi Bluetooth

Question 53

What are the two main frequencies for Wi-Fi?

Answer 53

2.4 and 5 GHz

Question 54

Advantages and disadvantages to 2.4Hz Wi-Fi?

Answer 54

Advantages: Larger range and coverage (longer wavelength) Works better at longer distances from WAP Better transmission through walls and other solid objects Disadvantages: Slower data transmission rates More interference from other devices using 2.4GHz - such as baby monitors, bluetooth Only 3 non-overlapping channels

Question 55

Advantages and disadvantages to 5Hz Wi-Fi?

Answer 55

Advantages: faster data transmission rates eg better for streaming videos Less crowded space with 23 non-overlapping channels Disadvantages: Shorter range so less able to penetrate through walls (hence need for extender device) Fewer devices can use the 5GHz frequency

Question 56

What are the advantages to Wi-Fi?

Answer 56

Portability - Easy to move around, location is only limited by range Cost - Less expensive to setup and add new devices Compatibility - Most devices are manufactured with a built in Wi-Fi adapter

Question 57

What are the disadvantages to Wi-Fi?

Answer 57

Speed - Slower data transfer than Ethernet Security - Less secure than Ethernet Range - Relies on signal strength to the WAP, signals can be obstructed (up to 90m)

Question 58

What is Bluetooth?

Answer 58

Bluetooth is a wireless method of connecting devices together over a short distance

Question 59

How does Bluetooth work?

Answer 59

A persistent link is made between the two devices A device can ask for a passkey in order to pair to it – this gives a layer of security like a password Passkeys only need to be entered once and will be remembered by devices that are paired

Question 60

Advantages to Bluetooth?

Answer 60

Compatibility - Ideal for personal devices and ad-hoc connections Power - Very low power consumption

Question 61

Disadvantages to Bluetooth?

Answer 61

Speed - Very slow transfer speeds Security - Data can be intercepted by anyone in range Range - Very short range (10m)

Question 62

What is encryption?

Answer 62

Encryption is a method of scrambling data before being transmitted across a network in order to protect the contents from unauthorised access

Question 63

Define these words: plaintext, ciphertext, encryption algorithm, key.

Answer 63

Plaintext: the original message to be encrypted Ciphertext: the encrypted message Encryption: the process of converting plaintext into ciphertext Key: a sequence of numbers used to encrypt or decrypt, often data using a mathematical formula Encryption algorithm: the formula for encrypting the plaintext

Question 64

What is symmetric encryption?

Answer 64

A single key is used to encrypt and decrypt a message and must be given to the recipient of your message to decrypt the data

Question 65

What is asymmetric encryption?

Answer 65

Two keys are used - one (public key) to encrypt and the other (private key) to decrypt data This is more secure as it means that you never have to send or reveal your decryption key

Answer 66

Step 1: SSID and Password are Used to Generate a Master Key A wireless network is identified by its SSID (Service Set Identifier). When a user enters the SSID and the correct password, the device and the router generate a unique encryption key, called the master key. This process uses a method known as the 4-way handshake (handled automatically by the network protocol). Step 2: Each Device Gets Its Own Copy of the Master Key Devices that connect to the network using the correct SSID and password are given a copy of the master key. This key is never sent across the network to prevent hackers from intercepting it. Step 3: The Master Key is Used to Encrypt the Data When a device sends data over the wireless network, the data is first converted into cipher text using the master key. Encryption scrambles the data so that it cannot be read by anyone without the key. Step 4: Encrypted Data (Cipher Text) is Transmitted Wirelessly The cipher text is sent through the air between the device and the wireless router. If anyone intercepts the signal, they will only see scrambled, unreadable data. Step 5: The Receiver Decrypts the Cipher Text Using the Master Key The receiving device uses the same master key to turn the cipher text back into plain text (the original readable data). This process is called decryption. Step 6: The Master Key is Never Transmitted The master key is kept secure and is never sent across the network. This ensures that even if someone intercepts the wireless data, they cannot decrypt it without the key. Step 7: WPA2 Protocol is Used for Wireless Security Wireless networks use encryption protocols like WPA2 (Wi-Fi Protected Access 2). WPA2 is designed to secure Wi-Fi communication, protect the master key, and ensure encrypted transmission.

Question 67

How is wired data encrypted?

Answer 67

Wired networks are encrypted in a very similar way to a wireless network, using a master key to encrypt data and the same key to decrypt data Encryption on a wired network differs slightly as it is often left to individual applications to decide how encryption is used, for example HTTPS

Question 68

What is an IP address?

Answer 68

An IP (Internet Protocol) address is a unique identifier given to devices which communicate over the Internet (WAN) IP addresses are dynamic, they can change IP addresses make it possible to deliver data to the right device A device connecting to a network will be given an IP address, if it moves to a different network then the IP address will change

Question 69

What is IPv4?

Answer 69

Internet Protocol version 4 is represented as 4 blocks of denary numbers between 0 and 255, separated by full stops Each block is one byte (8 bits), each address is 4 bytes (32 bits)

Question 70

What is IPv6?

Answer 70

Internet Protocol version 6 is represented as 8 blocks of 4 hexadecimal digits, separated by colons Each block is 2 bytes (16 bits), each address is 16 bytes (128 bits)

Question 71

What is a MAC address?

Answer 71

A MAC (Media Access Control) address is a unique identifier given to devices which communicate over a local area network (LAN) MAC addresses are static, they can never change MAC addresses make it possible for switches to efficiently forward data to the intended recipient Any device that contains a Network Interface Card (NIC) has a MAC address assigned during manufacturing

Question 72

How is a MAC address structured?

Answer 72

A MAC address is represented as 12 hexadecimal digits (48 bits), usually grouped in pairs The first three pairs are the manufacturer ID number (OUI) and the last three pairs are the serial number of the network interface card (NIC)

Question 73

What is a computing standard?

Answer 73

A computing standard is a set of guidelines that when used with different hardware and software allows them to work with each other (compatibility) and allow data exchange (interoperability)

Question 74

What are some examples of computing standards?

Answer 74

HTML - A standard for creating websites that allows them to be viewed on the World Wide Web (WWW) using web browser software Ethernet - A standard for wired network cables that allows the network to function USB - A standard that defines the physical connector used for connecting peripheral devices to computers Wi-Fi - A standard that allows wireless devices to communicate on a local area network (LAN)

Question 75

What is a protocol?

Answer 75

A protocol is a set of rules that govern communication on a network

Question 76

What is TCP and IP?

Answer 76

TCP/IP is two protocols, transmission control protocol (TCP) and internet protocol (IP) that combined allow communication over the internet (WAN) TCP is responsible for making sure communication between two routers is error free IP is responsible for making sure data is delivered to the right device on a wide area network (WAN)

Question 77

What is HTTP and HTTPS?

Answer 77

Hypertext Transfer Protocol (HTTP) allows communication between clients and servers for website viewing HTTP allows clients to receive data from the sever (fetching a webpage) and send data to the server (submitting a form, uploading a file) HTTPS works in the same way as HTTP but with an added layer of security. All data sent and received using HTTPS is encrypted HTTPS is used to protect sensitive information such as passwords, financial information and personal data

Question 78

What is FTP?

Answer 78

File Transfer Protocol (FTP) allows sending and receiving files between computers Uploading and downloading files to/from a web server is often completed using FTP FTP offers greater efficiency and support for bulk transfers and large files such as resuming interrupted transfers FTP clients are software applications that use the FTP protocol to make the process easier for users

Question 79

What is SMTP?

Answer 79

Simple Mail Transfer Protocol (SMTP) is a protocol that allows communication between an email sender and the email server, and between different email servers using the internet In the diagram above, SMTP is used to transfer the senders email to their email providers server and SMTP is used to transfer the email to the recipients email server

Question 80

What does the @ mean in an email?

Answer 80

The part of the email address after the "@" sign, virgin.com, is called the domain name. It identifies which mail server is responsible for receiving and managing the email. virgin is the domain name, which is unique to the organization (in this case, Virgin). .com is the top-level domain (TLD), which often indicates the type of organization. .com is typically used by commercial businesses, but there are other TLDs like .org for organizations, or .edu for educational institutions. When you send an email, the domain name helps route the message to the right server. So, when you send an email to simgirl@virgin.com, the email system looks up the domain virgin.com to find the correct mail server to deliver the message.

Question 81

What is POP?

Answer 81

Post Office Protocol (POP) is a protocol for downloading emails to a device from an email server Once the email has been retrieved it is removed from the server

Question 82

What is IMAP?

Answer 82

Internet Message Access Protocol (IMAP) is a protocol for downloading emails to a device from an email server Once the email has been retrieved, a copy is retained on the mail server

Question 83

What are the advantages and disadvantages of POP?

Answer 83

Advantages: Frees up storage space on email servers Faster on slow connections Disadvantages: Only access emails from the device they're downloaded to Emails deleted on the server once downloaded

Question 84

What are the advantages and disadvantages of IMAP?

Answer 84

Advantages: View and manage emails from any device with internet access Changes made on one device are synchronised on all connected devices Disadvantages: Server storage space can limit amount of retained emails Requires internet access to view emails

Question 85

What is a layer?

Answer 85

A layer is a sub part of a more complex task Dividing network tasks into layers reduces the complexity and makes each layer more manageable An example of layers can be seen in the TCP/IP protocol which uses a 4-layer model known as a 'stack'

Question 86

What does the application layer do?

Answer 86

Application layer: Applications such as email clients and web browsers create data to send in this layer

Question 87

What does the transport layer do?

Answer 87

Transport Layer: The Transport layer creates the connection between two computers, or ‘hosts’ (TCP)

Question 88

What does the Internet layer do?

Answer 88

Internet Layer: The Internet layer is responsible for routing packets (IP) Routers operate on this layer Source and destination addresses are written on to the packets ready for transmission

Question 89

What does the Link layer do?

Answer 89

Link layer: The link layer is the ​connection between the network devices​, it adds the MAC address​ identifying the ​Network Interface Cards​ of the source and destination computers. (MAC, Ethernet, Wi-Fi)

Question 90

How do data packets move up the layers upon arrival?

Answer 90

1. The link layer removes the MAC address and passes packets up to the Internet layer 2. The Internet layer removes the IP addresses and passes packets up to the Transport layer 3. The Transport layer reassembles the packets and passes the data to the Application layer 4. The Application layer uses the correct protocol to correctly display the data, web page or email for the user

Question 91

What are the advantages of layers?

Answer 91

Layers are self-contained which makes managing, repairing and upgrading easier as each layer can be worked on independent of other layers Layers allow for focus on specific parts of a protocol without affecting other layers Promotes data exchange (interoperability) between hardware and software