3.5 Computer Networks

Question 1

L1
1) What is a computer network?
2) What are the advantages of a computer network (state 5)?
3) What are the disadvantages of a computer network (state 5)?

Answer 1

1) A computer network is more than one computer connected together and able to share resources.
2) Advantages of a computer network:
- Software, storageand documents can be shared more easily across the network
- You can share devices, like printers
- Users can connect with people in other countries
- It can be more reliable
- Backups can be centralised
3) Disadvantages of a computer network:
- Networks are expensive to set up
- Hackers could gain access to an entire network if it isn’t protected
- Viruses can be spread through connections
- Managing security over an entire network requires specialist skills
- Managing a network requires specialist skills

Question 2

L1
1) What are the advantages of the peer-to-peer model?
2) What are the disadvantages of the peer-to-peer model?

Answer 2

1) Advantages of the peer-to-peer model:
- Clients are not dependent on one single server
- Resources can be shared between computers (e.g. printers)
- It doesn’t require expensive equipment to set up
- If more than one computer in the network hosts a file, then the client can request it from the device that is closest
2) Disadvantages of the peer-to-peer model:
- Using a shared peripheral, like a printer, can lead to a computer slowing down whilst processing many requests
- If a host computer breaks down, this can cause files or peripherals that are hosted by it to be unavailable
- There is no central backup system
- There is no central way to provide security for the network

Question 3

L2
1) Define server
2) Define client
3) What is the client-server model?
4) What is the peer-to-peer model?

Answer 3

1) Servers fulfil the requests from the client.
2) Clients make requests for the server.
3) In the client–server model, a dedicated server will fulfil requests for one or more clients.
4) With a peer-to-peer model, each device can perform the role of the client and the server.

Question 4

L2
1) What is a Personal Area Network (PAN)?
2) What is a Local Area Network (LAN)?
3) What is a Wide Area Network (WAN)?

Answer 4

1) PAN is limited to a single user in the network with multiple connected devices. It connects personal devices such as a smartwatch to a phone. An example is bluetooth. Examples of its uses include: connects headphones to a music player, or connecting a pedometer to a mobile phone.
2) LAN has multiple users and is typically situated in a single building or room. It covers relatively small geographical areas, and they are often owned and controlled or managed by a single person or organisation. In offices, LANs are often used to provide shared access to internal employees to connected printers or servers.
3) WAN is formed when devices are connected across a wider geographical area. These are often under collective or distributed ownership. The internet is the biggest example of a WAN. Companies use WANs to do the following: Communicate using voice and video. Share resources between employees and customers. Access data storage and remotely back up data.

Question 5

L2
1) What are the advantages of the server-client model?
2) What are the disadvantages of the server-client model?

Answer 5

1) Advantages of the server-client model:
- All of the files are stored on one central server
- All of the peripherals are processed via the server
- If a client machine breaks it won’t affect the whole network
- A backup can be taken of the server, rather than individual client machines
2) Disadvantages of the server-client model:
- They are expensive to set up, compared to stand-alone computers or a peer-to-peer network
- A specialist network administrator is required to set up the network
- If the server fails, then everyone connected to that server is disrupted

Question 6

L3
1) What is a wireless access point?
2) What is a router?
3) What is a switch?

Answer 6

1) A wireless access point (WAP) connects to a wired network and provides a wireless network radio signal for wireless devices to connect to. The WAP does not provide internet access, it only provides wireless access to the network.
2) Routers move data from one network to another. Routers are usually used to connect a network to the internet. A wireless access point and a router are both needed to connect to the internet.
3) A switch is needed if there are multiple wired connections on the network. The switch is responsible for connecting data to the correct wired device. A switch is only required if there are wired devices on the network.

Question 7

L3
1) Explain what a hub is
2) Explain what a network interface card is
3) Explain what a bridge is

Answer 7

1) A hub can be used to connect multiple wired devices together. A hub will take any incoming data and broadcast (copy and send) it to all other devices connected to the hub. There are potential security risks with a hub because the data is broadcast to all devices instead of the specific device that needs it.
2) A network interface card (NIC) enables a wired network connection between a computer and another networked device. Every network interface card has a unique address called a MAC address, which is used to locate devices on the network. MAC stands for media access control.
3) A bridge is used to connect a LAN to another LAN. A bridge helps to reduce the traffic in a network by segmenting the network. Data will only pass through the bridge to the other segment or LAN if it is required by that part of the network.

Question 8

L4
1) Define topology
2) What are graphs?
3) What are nodes and edges?

Answer 8

1) Topologies are the arrangements of devices and components in the network.
2) Graphs are used to represent the different topologies.
3) The nodes (dots) illustrate a component in the network, and the edges (lines) represent how they are connected to each other.

Question 9

L4
1) Explain the star topology
2) Explain the bus topology

Answer 9

1) The arrangement has one central node with all of the other nodes connected to it.
The central node would typically be a hub or a switch that could transfer data between nodes.
2) In this arrangement, each node is connected to a single cable, and data is sent in both directions. Terminators are placed at the end of the cable to stop the signal being reflected back down the cable. In a bus topology the data is sent to all nodes connected to the bus, but is only accepted by the node that requires it.

Question 10

L4
1) Explain the ring topology
2) Explain the mesh topology

Answer 10

1) In this arrangement, each node is connected in a ring. When data is transferred it moves around the ring in one direction. The data will continue to move around the ring until it reaches its destination.
2) In this arrangement, there are multiple ways for data to transfer from one node to another.
In a mesh network, each node is connected to at least one other node. Often, they are connected to more than one node. The most efficient route is typically calculated before transferring the required data.

Question 11

L5
1) What is a wireless access point?
2) Define transmission media
3) Define wired transmission media, and what is the diagram?
4) Define wireless transmission media, and what is the diagram?

Answer 11

1) A wireless access point (WAP) connects to a wired network and provides a wireless network radio signal for wireless devices to connect to.
2) Transmission media is the media used to transmit data from one device to another.
3) Wired transmission media is a physical cable that connects one device to another. This is often showm as a solid or a long dashed line in a graph or diagram.
4) Wireless transmission media doesn’t require a physical cable. Wireless signals are sent through the air. A wireless connection is often shown using a short dotted line or a wave signal (wifi logo).

Question 12

L6
1) What are the key factors that can affect network performance?
2) Define bandwidth
3) What is bandwidth measured in?

Answer 12

1) The key factors that can affect network performance are: bandwidth, latency, range, and the number of devices.
2) Bandwidth: The amount of data that can be transferred within a defined time period.
3) Bandwidth is typically measured in megabits per second (Mbps) or gigabits per second (Gbps).

Question 13

L6
1) Define latency
2) Define range
3) Define transmission rate

Answer 13

1) Latency: The time delay from sending data to when it is received.
2) Range: The maximum distance that data can travel along the transmission media.
3) Transmission rate: The speed at which data can travel, e.g. 10Gbps.

Question 14

L7
1) Define internet
2) Define protocol
3) Explain the TCP/IP protocol suite

Answer 14

1) The internet is a global network of networks.
2) A protocol is sets of rules used for communication.
3) TCP/IP transmission suite:
- TCP (transmission control protocol) deals with breaking data into packets, distributing them, and re-ordering them at the destination.
- IP (Internet Protocol) is responsible for making sure that the data arrives at the correct destination.

Question 15

L7
1) Define IP address
2) Explain the WWW
3) What is the DNS and why is it used?

Answer 15

1) A term used to describe the numeric pattern assigned to each device on a network. Used to locate devices. Every device on the internet has its own, unique IP address.
2) WWW stands for the World Wide Web. It is a collection of web pages that can be browsed using a web browser.
The internet and the WWW are not the same thing. The internet is a global network of computers all connected together. The world wide web (‘www’ or ‘web’ for short) is a collection of webpages found on this global network of computers. The internet can be used to access the WWW.
3) The DNS is a collection of servers that lists commonly used website addresses and their IP addresses. There are thousands around the world.
It is used because it would be very hard to remember the IP address of every website that you want to use, so a naming system (DNS) is used instead.

Question 16

L7
Explain how a computer finds the IP address for a website

Answer 16

1. First it checks with your ISP’s (Internet Service Provider) DNS server. This contains the most commonly visited website IP addresses that their customers view.
2. If the website’s IP address can not be found here then it checks the fastest available root DNS server. The root DNS server is at the very top of the DNS server hierarchy.
   It knows the location of all of the DNS servers on the top level domain (TLD).
3. If the computer is trying to access the IP address for a .com URL then it will go to the .com TLD server.
4. The .com TLD server will then have a list of all of the authoritative name servers (ANS). These are the web servers that use a .com extension.
5. The authoritative name servers (ANS) for Google will be able to tell your computer the IP address for google.com.

Question 17

L7
1) Define top level domain
2) Explain the URL structure

Answer 17

1) The top level domain (TLD) contains IP addresses for specific domain name extensions such as .com and .uk.
2) 1. First the root is checked. It is a hidden dot (.) at the end of the URL.
2. Next it checks the top level domain
3. Then it moves down the structure to find the DNS servers for .co. This is sometimes referred to as the 2nd level domain.
4. It finally goes to the authoritative name server for the domain (eg. youtube). This is sometimes referred to as the 3rd level domain.

Question 18

L8
1) Define web server
2) Define the cloud/ cloud computing

Answer 18

1) A web server is a server dedicated to providing services for the world wide web.
2) The cloud is a term used to describe software and storage that are used through the internet.

Question 19

L8
1) Define Software as a service (SaaS)
2) What are the advantages and disadvantages of cloud storage?

Answer 19

1) Software as a service (SaaS): Software that you can use on your devices that is hosted on servers elsewhere.
2) Advantages:
- Cloud storage has its own built in backup system to protect your files
- Data can be backed up automatically
- You can often get a small amount of storage for free
- It can save money on maintenance
Disadvantages:
- As your storage increases, you may need to pay a larger fee
- You have less control over your data
- It relies on an internet connection to access your data
- Switching cloud storage suppliers can be problematic

Question 20

L9
1) Define protocols
2) Define ethernet
3) Define ethernet cable

Answer 20

1) Protocols: A set of rules used for communication.
2) Ethernet: A suite of protocols used with wired networks. Any network hardware that uses this suite of protocols will work with any other hardware that uses them.
3) An ethernet cable can be used to describe copper and fibre optic cables that use the Ethernet suite of protocols.

Question 21

L9
1) Define WiFi
2) Define HTTP
3) Define HTTPS

Answer 21

1) A suite of protocols used with wireless networks. It enables the transmission of data through radio signals.
2) HTTP (Hypertext Transfer Protocol): It is a protocol that is used to identify, request, and transfer web pages across the internet.
3) HTTPS (Hypertext Transfer Protocol Secure): A secure version of this protocol that adds in extra protection for the data that is transmitted.

Question 22

L9
1) Explain FTP
2) Explain UDP
3) State what POP, IMAP, and SMTP protocols are used for?

Answer 22

1) FTP (file transfer protocol): deals with uploading and downloading files from a server.
2) UDP stands for User Datagram Protocol.
Messages are sent instead of packets - chunks - it is often faster. It allows for gaming or video calls over the internet.
3) POP, IMAP, and SMTP protocols all deal with email communications.

Question 23

L9
1) Define POP
2) Define IMAP
3) Define SMTP

Answer 23

1) POP stands for post office protocol. This type of email protocol is less common nowadays. The POP protocol retrieves the email from the email server, delivers it to your computer or device, and then deletes it from the email server.
2) IMAP stands for internet message access protocol. IMAP retrieves the email from the email server but also leaves a copy of it on the remote server.
3) SMTP stands for simple mail transfer protocol. This protocol deals with sending an email to an email server.

Question 24

L10
1) What is a TCP/IP suite?
2) What is the TCP/IP model?

Answer 24

1) TCP/IP is a suites of protocols that is used to transmit data over the internet.
- TCP (Transmission Control Protocol) deals with breaking data into packets, distributing them, and reordering them at the destination.
- IP (Internet Protocol) is responsible for making sure that the data arrives at the correct destination.
2) A model used to demonstrate how data is transmitted across the internet. The model has four layers: application, transport, internet, and link.

Question 25

L10
1) Explain the application layer
2) Explain the transport layer

Answer 25

1) This is the first step in the TCP/IP model. encodes/decodes the message into a form that is understood by the sender and the recipient devices using protocols such as HTTP, FTP and SMTP.
2) This is the second step in the TCP/IP model. The transport layer checks if the data needs to be broken down into segments. If so, it performs this operation. Once the data has been divided into segments, a header is added with information about the protocol used (either TCP or UDP) and the sender and receiver port numbers.

Question 26

L10
1) Explain the internet layer
2) Explain the link layer

Answer 26

1) This is the third step in the TCP/IP model. The internet layer deals with the IP protocol. It uses this to create IP packets from the data passed into it from the transport layer. The IP packet has a header that lists the sender and receiver IP addresses.
2) This is the last step in the TCP/IP model. The link layer deals with the physical transmission of the data. It creates frames from the IP packets passed to it from the internet layer. These frames include a header that lists the protocol used for the technology that is used from the current node to the next node on the network. It also lists the destination MAC address.

Question 27

L10
What layers in the TCP/IP model do the following protocols operate at:
1) The transport layer (state 2)
2) The link layer (state 2)
3) The application layer (state 6)
4) The internet layer (state 1)

Answer 27

1) TCP, UDP
2) Ethernet, WiFi
3) HTTP, HTTPS, IMAP, SMTP, POP, FTP
4) IP

Question 28

L11/12
1) Why do networks need protection?
2) What are the two main forms of attack?
3) What is social engineering?

Answer 28

1) Networks are extremely vulnerable to attack. This is because they can:
- Span large geographical areas
- Have large numbers of users
- Be expensive to maintain and keep up to date with the latest security threats
2) There are two main forms of attack that can happen to a network. These are:
- Social engineering
- Malicious software
3) Social engineering is a set of methods used by cyber criminals to deceive individuals into handing over information that they can use for fraudulent purposes.

Question 29

L11/12
1) What is fishing?
2) What is blagging?
3) What is shouldering?

Answer 29

1) Phishing is when an attacker sends fraudulent emails to large groups of people in an attempt to get them to click a link to a site that encourages them to enter their personal details.
2) Blagging is when an attacker invents a scenario in order to convince the victim to give them data or money. This attack often requires the attacker to maintain a conversation with the victim until they are persuaded to give up whatever the attacker has asked for.
3) Shouldering is an attack designed to steal a victim’s password, or other sensitive data. It involves the attacker watching the victim provide sensitive information.

Question 30

L11/12
1) What is malicious software?
2) What is DDoS?
3) What is pharming?

Answer 30

1) Malicious software (malware) is software that is designed to cause harm to a network. Types of attack include:
- Distributed denial of service attacks (DDoS)
- Pharming
- Viruses
- Trojans
2) A distributed denial of service attack (DDoS) is when a server gets flooded with traffic in order to overwhelm it and disrupt the service. This can cause the website to load more slowly or even stop it being accessed at all.
3) A pharming attack is when malware redirects the victim to a malicious version of a website.

Question 31

L11/12
Explain the methods used to protect a network (state 5)

Answer 31

It is important that users are trained to identify potential signs of attack.
Network administrators can give users different levels of access to the network. Users should only have the level of access that they need to perform their role.
There are many other ways to protect a network. These include:
- Anti-malware software
- Firewalls
- Penetration testing
- Physical security
- Backup and recovery