1.3.3 - Networks

Question 1

What is a protocol?

Answer 1

A set of rules to control and govern communication between devices on a network.

Question 2

What is a network

Answer 2

Two or more devices that are interconnected and can communicate with each other.

Question 3

What is a standard

Answer 3

A set of hardware and software specifications that allow manufacturers to create products and services that are compatible with each other.

Question 4

What is an IP Address?

Answer 4

A numerical address made of 4 numbers each between 0 and 255 that uniquely identifies a device on a network.

Question 5

What is a MAC address

Answer 5

‘Media Access Control’ addresses
which are unique to a device that are used to identify each device on the network.

Question 6

Explain how the Domain Name System (DNS) plays a role in websites being loaded.

Answer 6

• DNS is used to resolve IP corresponding to URL
• Request sent to DNS resolver.
• Resolver checks its cache and if it doesn’t hold the URL, it passes it in to the TLD Name server which checks its cache and returns the answer or passes it on to the Authoritative Name Server.
• The IP address is returned back up to the requesting client Or an error if no resolution can be found.

Question 7

What is a LAN?

Answer 7

‘Local Area Network’- A group of devices connected over a small geographical area. The infrastructure is usually owned by the network owner.

Question 8

What is a WAN?

Answer 8

‘Wide Area Network’ - Collection of connected computers/devices over a large geographical area often using 3rd party communications channels

Question 9

What is more secure LAN or WAN

Answer 9

LAN

Question 10

What is the structure of a data packet

Answer 10

• Header: Sender’s/transmitting IP address, Receiver’s/destination IP address, Protocol, Packet number and order, i.e. the place of the packet in the complete message.
• Payload: The actual data file to be transmitted.
• Trailer: End of packet marker, Error correcting code

Question 11

Explain what is meant by packet switching

Answer 11

• Data is split into chunks called packets which have labels including address being sent to and the order its arranged into.
• Each packet is sent on the most convenient route meaning they may arrive in a different order to which they were sent.
• Once packets arrive at receiver they are reordered.

Question 12

Explain what is meant by circuit switching

Answer 12

• Physically connects devices together
• Devices remain connected for the duration of data transmission.
• Establishes a route before transmission between the two computers for the duration of the message.
• Sends all packets on the same reserved route down the circuit in order.
• Packets remain in correct order but must be reassembled at the destination.

Question 13

Firewalls

Answer 13

A computer application used in a network to prevent external users gaining unauthorised access to a computer system.

Question 14

Proxies.

Answer 14

A computer application that has accesses to data on a different computer system or network. It controls the access of unauthorised. users to data and allows the operation of the system to be isolated from control by external users.

Question 15

Encryption

Answer 15

The process of making data in a computer system unintelligible.

Question 16

TCP/IP Stack

Answer 16

Transmission Control Protocol / Internet Protocol:

The most common general-purpose standard protocol that allows any networked computers (including those on the internet) to communicate with each other no matter their equipment.

Question 17

Protocol Layering

Answer 17

The concept of a protocol not simply being a set of rules, but those rules being built up into very specific layers and those rule layers behind build on top of each other in a deliberate order creating a layered protocol stack. This results in the rules of a protocol being executed in a specific sequence as you move through the protocol stack.

Question 18

DNS

Answer 18

Domain Name System
- DNS is used to resolve IP corresponding to URL
- Request sent to DNS resolver.
Resolver checks its cache and if it doesn’t hold the URL, it passes it in to the TLD Name server which checks its cache and returns the answer or passes on to the Authoritative Name Server
- The IP address is returned back up to the requesting client or an error if no resolution can be found

Question 19

2 Types of Network Topology + Examples

Answer 19

• Physical - The physical layout of wires and components that form a network. E.g. Bus, Star, Mesh
• Logical - The layout which shows how data flows. E.g. LAN and WAN

Question 20

Physical Bus Topology (Hint - ABB Bus)

Answer 20

All the terminals (devices) are connected to a backbone cable, the ends of which are plugged into a terminator

Question 21

Advantages of Bus Topology

Answer 21

• Relatively inexpensive to set up
• Doesn’t require any additional
  hardware

Question 22

Disadvantages of Bus Topology

Answer 22

• If backbone cable fails, the entire
  network gets disconnected
• As traffic increases, performance
  decreases
• All computers can see the data
  transmission

Question 23

Physical Star Topology

Answer 23

• Star topologies use a central node, often a switch, to direct data through the network.
• MAC addresses are used to identify each device on the network.

Question 24

Advantages of Star Topology

Answer 24

• Performance is consistent even with
  heavy network traffic
• If one cable fails, only that single
  terminal is affected
• Transmits data faster, giving better
  performance than bus topology
• Easy to add new stations.
• No data collisions

Question 25

Disadvantages of Star Topology

Answer 25

• Expensive due to switch and cabling
• If the central switch fails, the rest of
  the network fails

Question 26

Physical Mesh Topology

Answer 26

Disadvantages of Star Topology

Question 27

Advantages of Mesh Topology

Answer 27

• If using a wireless network, there is
  no cabling cost
• As the number of nodes increase,
  the reliability and speed of network
  becomes better
• Nodes are automatically
  incorporated
• Nodes don’t go through a central
  switch, improving speed

Question 28

Disadvantages of Mesh Topology

Answer 28

• If using a wireless network, devices
  with wireless capability (which
  increases cost) must be purchased
• If using a wired network, a large
  quantity of cable is required
  compared to other network
  topologies like bus and star. This is
  expensive.
• Maintaining the network is difficult

Question 29

Client Server

Answer 29

Terminals known as clients connected to a server. The server is a powerful, central computer. The server holds all of the important information and resources and has greater processing power than the terminals. Clients can request to use the server.

Question 30

Advantages of Client-Server

Answer 30

• 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 31

Disadvantages of Client-Server

Answer 31

• 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 32

Peer to Peer Server

Answer 32

• A network in which computers are connected to each other so that they can share files.
• Each device effectively acts as both a server and client, as it can both provide and request
  resources.
• Peer-to-peer networks are used in piracy, since it’s almost impossible to trace
  the origin of files.

Question 33

Advantages of Peer-to-peer

Answer 33

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

Question 34

Disadvantages of Peer-to-peer

Answer 34

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