1.3.3 Networks

Question 1

What is circuit switching?

Answer 1

A method for sending data between two nodes on a network by creating a dedicated communication channel first. All data follows this same path for the duration of communication.

Question 2

What is a client-server network?

Answer 2

A type of network organisation where networked computers (clients) connect to one or more powerful central computer (servers) that handles service requests and has resources

Question 3

What is a domain name system (DNS)?

Answer 3

A hierarchical naming system that maps human-readable domain names to IP addresses that locate and identify resources on a network.

Question 4

What is encryption?

Answer 4

The process of converting the orginal data (plaintext) into a form which cannot be understood by unauthorised users (ciphertext) using an encryption algorithm (cipher)

Question 5

What are firewalls?

Answer 5

A security checkpoint application that monitors incoming and outgoing network traffic, designed to prevent external users from gaining unauthorised access between two networks.

Question 6

What are local area networks (LANs)?

Answer 6

A network connecting a group of computing devices on a single geographical area/site

Question 7

What is packet switching?

Answer 7

A method for sending data over a network by breaking data into several data packets which are sent independently and then reassembled once they all reach their destination.

Question 7

What is a peer to peer network?

Answer 7

A type of network organisation where networked computers are connected to each other and share resources and workloads without any central server.

Question 8

What is protocol layering?

Answer 8

A technique that simplifies network design by dividing a complex system into its components’ functional layers and assigning protocols for each layer to perform tasks and communicate with adjacent layers.

Question 9

What are proxies?

Answer 9

A server application that intercepts all data packets entering and leaving a network to hide the true network addresses of the source from the recipient. They also restrict authorised users’ access to data and isolates the network from external networks (like the internet)

Question 10

What is a wide area network (WANs)?

Answer 10

A network connecting a group of computing devices over a large geographical area, typically with the help of third party centres.

Question 11

What is a protocol?

Answer 11

A protocol is a set of rules defining how two computers communicate with each other.

Question 12

Why are protocols used?

Answer 12

Protocols are standard so that all devices have a designated method of communicating with each other, regardless of manufacturer.

Question 13

What is HTTP?

Answer 13

(Hypertext Transfer Protocol) – Used for web page rendering, an encrypted version
HTTPS (Secure), is becoming more common

Question 14

What is TCP/IP?

Answer 14

(Transmission Control Protocol / Internet Protocol) – This is a networking protocol used in the routing of packets through networks

Question 15

What are POP3 and IMAP?

Answer 15

POP3 (Post Office Protocol) and IMAP (Internet Message Access Protocol) Mailing protocols, used for email access.

Question 16

What is FTP?

Answer 16

(File Transfer Protocol) – Used for the transmission of files over networks.

Question 17

What is the internet?

Answer 17

The Internet is a network of networks which allows computers on opposite sides of the globe to communicate with each other.
Continents are connected to each other using large international backbone cables.

Question 18

What is the TCP/IP stack?

Answer 18

TCP/IP stands for Transmission Control Protocol / Internet Protocol. A stack of networking protocols that work together passing packets during communication using 4 layers

Question 19

What is the network layer in the IP/TCP stack?

Answer 19

Adds the source and destination IP addresses.
Routers operate on the network layer, and the router is what uses the IP addresses to forward the packets.
The sockets are used to specify which device the packets must be sent to and the application being used on that device.

Question 19

What is the application layer in the IP/TCP stack?

Answer 19

The application layer is at the top of the stack. It specifies what protocol needs to be used to relate to the application that’s being sent.
For example, if the application is a browser, then it would select a protocol such as HTTP, POP3, FTP

Question 19

What is the transport layer in the IP/TCP stack?

Answer 19

Uses TCP to establish an end-to-end connection between the source and recipient computer.
It splits data up into packets and labels these packets with their packet number, the total number of packets the original data was split up into and the port number being used for communication.
If packets get lost, the transport layer requests retransmissions of these lost packets.

Question 19

What is the link layer in the IP/TCP stack?

Answer 19

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. For devices on the same network, the destination MAC address is the address of the recipient computer, otherwise, it will be the MAC address of the router.

Question 20

What is within the header of a packet?

Answer 20

Sender and recipenet IP addresses
Protocol being used
Order of packets
Time to live/hop limit

Question 20

What are the sender and recipient IP addresses ?

Answer 20

The sender and the recipient’s IP addresses act like a postcode, allowing the packet to be delivered to the correct destination and enabling the recipient device to trace where the packet came from.

Question 21

What si the time to live/hop limit?

Answer 21

The Time To Live (TTL), tells the packet when to expire so that it does not travel forever.

Question 22

What is the payload?

Answer 22

Raw data to be transmitted

Question 23

What is the trailer?

Answer 23

Checksum, or cyclic redundancy check The trailer contains a code used to detect whether any errors have occurred during transmission.

Question 24

What do data packets contain?

Answer 24

Header Payload Trailer

Question 25

What are 3 advantages of packet switching?

Answer 25

Multiple methods to ensure data arrives intact, eg. checksums and cyclic redundancy checks Multiple routes can be used between devices, so if one path breaks, another can be used. Packets can be transferred over very large networks to allow communication globally.

Question 26

What are 2 disadvantages of packet switching?

Answer 26

Time is spent deconstructing and reconstructing the data packets Must wait for all packets to arrive before data can be received.

Question 27

What are 2 advanatges of circit switching?

Answer 27

Data arrives in a logical order which results in a quicker reconstruction of the data. Enables two users to hold a call without delay in speech.

Question 28

What are 4 disadvantages of circuit switching?

Answer 28

Bandwidth is wasted during periods of time in which no data is being sent. Devices must transfer and receive data at the same rate. Using switches means electrical interference may be produced, which can corrupt or destroy data. Ties up sections of the network which cannot be used by others data until transmission has been completed

Question 29

What is pakcet filtering/static filtering?

Answer 29

Packet filtering / static filtering limits network access in accordance with administrator rules and policies. It works by examining the source IP, destination IP and the protocols being used as well as the ports being requested.

Question 30

What 2 things can happen when acess is denied by a firewall?

Answer 30

The packet can either be dropped or rejected. A rejected packet sends an alert to the sender to notify them of the error whereas a dropped packet will not.

Question 31

What are 4 benefits of using proxies?

Answer 31

The privacy of the user is protected and they remain anonymous The proxy server can cache frequently used website data making it faster to load Proxies can reduce overall web traffic Can be used by administrators to prevent access to sensitive or irrelevant information at work or at school

Question 32

What is a network interfcae card?

Answer 32

A network interface card is the card required to connect a device to a network. This is usually built into the device and assigns a unique media access control (MAC) address to each device.

Question 33

What is a MAC address?

Answer 33

A MAC address is a 48-bit value coded into the device and is usually written as a twelve digit hexadecimal number.

Question 34

What is a switch?

Answer 34

A switch is a device used to direct the flow of data across a network. Switches are most commonly used in networks using a star topology.

Question 35

What is a wireless access point (WAP)?

Answer 35

This is a device which allows a device to connect to a network. It is more commonly combined with a router to enable internet access. These are used in mesh networks.

Question 36

What is a router?

Answer 36

A router is used to connect two or more networks together. Routers allow private, home networks to connect to the Internet.

Question 37

What is a gateway?

Answer 37

A gateway is used when protocols are not the same between networks. It translates the protocols so that networks can communicate with each other.

Question 38

How to gateways work?

Answer 38

Gateways work by removing the header from packets before adding the data to packets using the new protocol.

Question 39

What are 3 advantages of client-server?

Answer 39

More secure, as data is stored in one location Central backups are carried out so there is no need for individual backups Data and resources can be shared between clients

Question 40

What are 3 disadvantges of client-servers?

Answer 40

Relatively expensive to set up Functionality of terminals depends on the server; if this fails, performance falls Trained staff are required to maintain the server

Question 40

What are 5 advantages of peer-to-peer?

Answer 40

Cheaper to set up Allows users to share resources Easy to maintain Not dependent on a central server Specialist staff are not required

Question 41

What are 4 disadvantages of peer-to-peer?

Answer 41

Impossible to trace the origin of files Backups must be performed separately Poorer security May be difficult to locate resources