Section 2: Networks

Question 1

What is a LAN?

Answer 1

A local are network, covering a small geographical are.

Question 2

Whats the Advantages of using a LAN?

Answer 2

1) Sharing files is easier.
2) You can share hardware like printers on a LAN.
3) The internet connection can be shared between every device on a LAN.
4) You can install and update software on all computers at once, rather than one-by-one.
5) You can communicated with LAN users cheaply and easily with instant messaging.
6) User accounts can be stored centrally, so users can log in from any device on the network

Question 3

What is a WAN?

Answer 3

A wide are network connecting LANs that are in different geographical locations. Organisations hire infrastructure (e.g. communication lines) which make using a WAN more expensive than a LAN. They may be connected using fibre or copper telephone lines, satellite links or radio links.

Question 4

What factors can affect the performance of a network and how?

Answer 4

1) Bandwidth is the amount of data that can be transferred in a given time. The greater the bandwidth, the better the network can perform.
2) Too many users or heavy use may cause congestion as bandwidth is used up or shared, slowing the network down.
3) Wired connections are generally faster and more reliable than wireless. Fibre optic cables can give much better performance than copper cables.
4) Wireless performance depends on signal quality si us affected by the range of the device, the amount of interference and physical obstructions
5) Choice of hardware other than cables and network topology also have a big affect.

Question 5

What 4 main parts of hardware is used to create a network?

Answer 5

NICs, Switches, Routers and Cables.

Question 6

What is a NIC?

Answer 6

A Network Interface Controller is an internal piece of hardware that allows a device to connect to a network.
They exist for both wired and wireless connections.

Question 7

What is a Switch?

Answer 7

Switches connect devices on a LAN. Switches receive data from one device and transmit this data to the device on the network with the correct MAC address.

Question 8

What is a Router?

Answer 8

Routers are responsible for transmitting data between networks - they’re always connected to at least two networks.

Question 9

What types of cables are used in networks and how are they different?

Answer 9

1) The most common ethernet cables are CAT 5e and CAT 6, they are twisted pair cables, containing four pairs of copper wires which are twisted together to reduce internal interference.
2) Coaxial cables are made of a single copper wire surrounded by a plastic layer for insulation and a metallic mesh which provides shielding from outside interference.
3) Fibre optic cables transmit data as light. they are high performance and therefore expensive cables - they don’t suffer interference and can transmit over very large distances without loss of signal quality.

Question 10

What is wireless and how does it transmit data?

Answer 10

Wireless uses radio waves to transmit data. To set up a wireless network, you need a Wireless Access Point (WAP) device. Devices need wireless capability. This is usually built in but if not you can use a USB dongle.

Question 11

How does WiFi work?

Answer 11

Wi-Fi uses two radio frequency bands - 2.4 GHz and 5 GHz.
2.4 GHz has a greater range and is better at getting through walls, while 5 GHz is faster over short distances.
The bands are split into numbered channels that each cover a small frequency range. The channels in the 2.4 GHz band overlap.
Wi-Fi performance is affected by interference between networks using adjacent channels. To avoid problems, only certain channels that are spaced apart then to be used. The 5 GHz band has more non-overlapping channels than the 2.4 GHz band, so there’s less chance of interference.

Question 12

What is a Client-Server network?

Answer 12

A client-server network is managed by a server. The devices connected to the server are the clients.
Files and software are usually stored centrally.
Clients send requests to the server e.g. asking for data. The server processes the request and responds. This is the client-server relationship.
The server stores user profiles, passwords and access information - it may request a password befroe fufilling certain requests.

Question 13

What are the advantages and disadvantages of client-server networks?

Answer 13

ADV:
1) Easier to keep track of files as they are stored centrally.
2) Easier to perform back-ups
3) Easier to install and update software
4) Easier to manage network security
5) Servers are very reliable and are always on
DISADV:
1) Expensive to set up and needs IT specialists to maintain the network and server.
2) Server dependence - if the server goes down all clients lose access to their work.
3) The server may become overloaded if too many clients are accessing it at once.

Question 14

What is a Peer-to-Peer network?

Answer 14

In peer-to-peer networks all devices are equal, connecting directly to each other without a server.
You store files on individual devices and share them with others.

Question 15

What are the advantages and disadvantages of Peer-to-Peer networks?

Answer 15

ADV:
1) Easy to maintain - you don’t need any expertise or expensive hardware
2) No dependence on server - if one device fails the whole network isn’t lost.
DISADV:
1) No centralized management - devices need their updates and security installed individually.
2) Copying files between devices creates duplicate files - its easy to lose track of what is stored where.
3) Peer machines are less reliable and data may be lost if one fails.
4) Machines are prone to slowdown when other devices access them.

Question 16

What are the advantages and disadvantages of a Star Topology?

Answer 16

ADV:
1) If a device fails or a cable is disconnected, the rest of the network is unaffected.
2) It’s simple to add more devices to the network.
3) Better performance than other setups - data goes straight to the central device so all devices can transmit data at once. and there are very few data collisions.
DISADV:
1) In wired networks, every device needs a cable to connect to the central switch or server. This can be expensive.
2) If there is a problem with the switch or server then the whole network is affected.

Question 17

What is the main advantage and main disadvantage of a mesh topolgy?

Answer 17

The main advantage is that there is no single point where the network can fail, If one device fails then the data is sent along a different route to get to its target.
The main disadvantage is that they are very expensive you need a lot of wire to connect so many devices together.

Question 18

What is a protocol?

Answer 18

A protocol is a set of rules or how devices communicate and how data is transmitted across a network.

Question 19

What is a MAC address?

Answer 19

Every device needs a unique identifier so it can be found on a network - this is its MAC address.
Mac addresses are assigned to all network-enabled devices by the manufacturer. They are unique and cannot be changed.
They are 48 or 64 bit binary numbers, to make them easier to understand they’re converted into hexadecimal.

Question 20

When are IP addresses used? What is the difference between static and dynamic IP addresses?

Answer 20

IP addresses are used when sending data between TCP/IP network e.g. over the internet.
Unlike MAC addresses, IP addresses aren’t linked to hardware. They are assigned either manually or automatically before the device can access the network.
Static IP addresses are permanent addresses. They’re used to connect printers on a LAN, and for hosting websites on the internet.
Dynamic IP addresses are assigned when a device logs on to a network, meaning that it may have a different address every time it connects.
IP addresses can either be a 32 bit or 128 bit binary number, 32 bits are converted into 4 DENARY numbers whilst the 128 bit are converted into 8 HEXADECIMAL numbers.

Question 21

How is data sent across networks?

Answer 21

Data sent between networks is split into equal-sized packets. Every data packet has a header - this contains control information (destination address, source address and packet number). The data packet’s payload is the reason the packet has been sent in the first place, e.g. an email, document, web page or streamed video. Packets are also likely to include a checksum number - a form of validation used to check the data hasn’t been corrupted. A function is performed on both the payload data before and after transmit, if the checksum numbers match, the data hasn’t been corrupted.

Question 22

What is packet switching?

Answer 22

Packet switching is used by routers to direct packets on the internet and other IP networks.

1) The sending device splits the data into packets to be sent across the network. Each packet is given a packet number to show the order of the data.
2) Each router reads the packet header and decides which way to send the packet next, according to the IP rules.
3) The way the data is sent changes depending on network traffic so the packets can take different routes. If a router receives too many packets at once it may prioritizes some over others.
4) As the packets take different routes, they can arrive in the wrong order. The receiving device uses the packet numbers to reassemble them in the right order,
5) Sometimes packets go missing in transit so the receiving device checks periodically that all packets have been received. If it hasn’t received them within a certain time, it sends ta timeout message back to the sending device.
6) If all the data is received and the checksums match, a receipt confirmation is sent to the sending device.

Question 23

What is TCP? (protocol)

Answer 23

Transmission control protocol sets the rules for how devices connect on the network. Its in charge of splitting data into packets and reassembling the packets back into the original data once they reach the receiving device. It’s also responsible for checking the data is correctly sent and delivered.

Question 24

What is IP? (protocol)

Answer 24

Internet protocol is responsible for packet switching.

Question 25

What 6 other protocols are there and what are they used for?

Answer 25

HTTP - Hyper Text Transfer Protocol - Used by web browsers to access websites and communicates with web server. HTTPS - HTTP Secure - A more secure version of HTTP. Encrypts all information sent and received. FTP - File Transfer Protocol - Used to access, edit and move files between devices on a network, e.g. to access files on a server from a client computer. POP3 - Post Office Protocol Version 3 - Used to retrieve emails from a server. The server holds the email until you download, at which point it is deleted from the server. IMAP - Internet Message Access Protocol - Used to retrieve emails from a server. The server holds the email until you actually delete it - you only download a copy. SMTP - Simple Mail Transfer Protocol - Used to send emails. Also used to transfer emails between servers.

Question 26

What are layers? (protocols)

Answer 26

A layer is a group of protocols which have similar functions. Layers are self-contained - protocols in each layer do their job regardless of other layers. Each layer serves the layer above it - it does the hidden work needs for an action on the layer above.

Question 27

What are the 4 layers and what do they do?

Answer 27

Layer 4 - Application layer - Turning data into websites and other applications and vice versa. - HTTP, FTP, SMTP Layer 3 - Transport layer - Controlling data flow - e.g. splitting data into packets and checking packets are correctly sent and delivered. - TCP Layer 2 - Network layer - Making connections between networks, directing data packets and handling traffic. Used by routers. - IP Layer 1 - Data link layer - Passing data over the physical network. Responsible for how bits are sent as electrical signals over cables, wireless and other hardware. - Ethernet.

Question 28

What are the advantages of Layers?

Answer 28

1) It breaks network communication into manageable pieces. 2) As layers are self-contained, they can be changed without the other layers being affected. 3) Having set rules for each layer forces companies to make compatible, universal hardware and software.

Question 29

What is an DNS?

Answer 29

A Domain Name Server translates a website's domain name into its IP address.

Question 30

What is the cloud?

Answer 30

The cloud uses the internet to store files and applications through 'Hosting'. It acts like an extension of a traditional client-server network where user files are stored centrally on a network server.

Question 31

What are the advantages and disadvantages of the cloud?

Answer 31

ADV: 1) Users can access files from any connected device. 2) Easy to increase how much storage is available 3) No need to buy expensive hardware to store data 4) No need to pay IT staff to manage the hardware 5) Cloud host provides security and back ups for you 6) Cloud software will be updated automatically DISADV: 1) Need connection to the internet to access files. 2) Dependent on host for security and back-ups. 3) Data in the cloud can be vulnerable to hackers. 4) Unclear who has ownership over cloud data 5) Subscription fees for using cloud storage and software may be expensive.

Question 32

What is a virtual network?

Answer 32

A virtual network is a network that is entirely software based. Virtual networks are created by partitioning off some of a physical network's bandwidth to form a separate network.

Question 33

What 5 types of network attacks are there?

Answer 33

1) A passive attack - Where someone monitors data travelling on a network. To counteract use data encryption. 2) An active attack - When someone attacks a network with malware. To counteract use a firewall. 3) An inside attack - Where someone within an organisation exploits their network acccess. 4) A brute force attack - Cracking passwords through trial and error 5) A denial-of-service attack - (DoS) is where a hacker tries to stop users from accessing a part of a network usually through flooding the network with useless traffic.

Question 34

What is Malware and give the 6 main actions of malware.

Answer 34

Malware is software that can harm devices, typical actions of malware include: 1) Deleting or modifying files. 2) Scareware - Lying to scare people and to get them to pay big amounts to fix fake problems. 3) Locking files - ransomware encrypts all files on a computer, a demand for a large sum of money is received in exchange for the decryption key. 4) Spyware - secretly monitors users actions e.g. key presses 5) Rootkits alter permissions, giving malware and hackers administrator-level access to devices. 6) Opening backdoors - holes in someone's security which can be used for future attacks.

Question 35

What 3 ways can malware access you device?

Answer 35

1) Viruses attach (by copying themselves) to certain files. Users spread them by copying infected files and activate them by opening infected files. 2) Worms spread like viruses but they self-replicate without any user help, meaning they can spread very quickly. They exploit weaknesses in network security. 3) Trojans are malware disguised as legitimate software. Unlike viruses and worms, they don't replicate - users install them not realising they have a hidden purpose.

Question 36

What is social engineering and give some examples.

Answer 36

Social engineering is a way of gaining sensitive information or illegal access to networks by influencing people, usually the employees of large companies. 1) Over the telephone - someone rings up an organisation and pretend to be a network administrator or someone within power. They then gain the employee's trust and persuades them to disclose confidential information. 2) Phishing - Criminals send emails or texts to people claiming to be from a well-known business. They then request for an update of personal information. When the user inputs this data into the website (linked in the email) criminals can then access their genuine account.

Question 37

What is an SQL injection?

Answer 37

Networks which make use of databases are vulnerable to SQL injections. SQL injections are pieces of SQL typed into a website's input box which then reveal sensitive information.

Question 38

What things will a good network policy do?

Answer 38

1) Regularly test the network to ind and fix security weaknesses. 2) Use passwords to prevent unauthorised people from accessing the network. 3) Enforce user access levels to limit the amount of people with access to sensitive information. 4) Install anti-malware and firewall software to prevent or destroy malicious software attacks. 5) Encrypt sensitive data.

Question 39

What is Pentesting and when is it used?

Answer 39

Penetration testing is when organisations employ specialists to simulate potential attacks on their network. Pentesting is used to identify possible weaknesses in a networks security by trying to exploit them.

Question 40

What is Network forensics and when is it used?

Answer 40

Network forensics are investigations undertaken to find the cause of attacks on a network . To conduct network forensics, an organisation needs to have a system of capturing data packets as they enter their network. After the network is attacked, these packets can be analysed to discover how the network was attacked and decide how to prevent future attacks.

Question 41

How can passwords be used?

Answer 41

Passwords help provide unauthorised users accessing the network. Passwords should be strong and should be changed regularly.

Question 42

What are user access levels and how can they be used?

Answer 42

User access levels control which parts of the network different groups of users can access. User access levels help limit the number of people with access to important data, so help prevent insider attacks on the network.

Question 43

What is Anti-malware software and how can it be used?

Answer 43

Anti malware software is designed to find and stop malware from damaging an organisation's network and the devices on it. Companies use firewalls to block unauthorised access. Firewalls examine all data entering and leaving the network and block any potential threats.

Question 44

What is encryption and how can it be used?

Answer 44

Encryption is when data is translated into a code which only someone with the correct key can access, meaning unauthorised users cannot read it. Encrypted text is called cipher text, whereas data which has not been encrypted is called plain text. Encryption is essential for sending data over a network securely.