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Computer Science Paper 1 > Networks > Flashcards

Networks Flashcards

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1
Q

What is a Network

A

Two or more computers connected together that can transmit data

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2
Q

What is a Physical Topology

A

The physical layout of the network

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3
Q

What is a Logical Topology

A

The topology that describes the way in which data flows around a network

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4
Q

Describe the Line/Bus Topology and it’s advantages and disadvantages

A

Bus Topology

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

Advantages

  • Relatively not expensive to set up
  • Doesn’t require any additional hardware as all the terminals are connected to a backbone cable

Disadvanatages

  • Dependent on backbone cable
  • As traffic increases, performance decreases
  • All computers can see the data transmission
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5
Q

Describe the Ring Topology and it’s advantages and disadvantages

A

Ring Topology

  • This network creates a circular data path, packets of data travel from one device to the next until they reach their destination

Advantages

  • Data flows in one direction which reduces the chance of packet collisions
  • It is cheap to install and expand

Disadvantages

  • Total dependence on one cable.
  • Addition and removal of any node during a network is difficult
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6
Q

Describe the Star Topology and it’s advantages and disadvantages

A

Star Topology

  • Uses a central node, often a switch, to direct data through the network

Advantages

  • Transmits data faster with no data collisions
  • Not dependent on one cable
  • Easy to add new stations without disrupting network

Disadvantages

  • Expensive due to switch and cabling
  • If the central switch fails, the rest of the network fails
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7
Q

Describe the Mesh Topology and it’s advantages and disadvantages

A

Mesh Topology

  • Every node is connected to every other node

Advantages

  • As the number of nodes increase, the reliability and speed of network becomes better
  • Improved speed as nodes don’t go through a central switch

Disadvantages

  • If using a wireless network, devices with increases cost must be purchased
  • If using a wired network, a large quantity of cable is required compared to other network topologies . This is expensive.
  • Maintaining the network is difficult
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8
Q

What are Protocols

A

Sets of rules defining how two devices communicate with each other

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9
Q

Why are Protocols Standard

A

Allows all devices to communicate by ensuring they all follow the same rules so they communicate in the same way

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10
Q

Describe the Examples of Commonly Used Protocols

A
  • HTTP (Hypertext Transfer Protocol) – Used for web page rendering
  • TCP/IP (Transmission Control Protocol / Internet Protocol) – Used in the routing of packets through networks
  • POP3 (Post Office Protocol) and IMAP (Internet Message Access Protocol) – Mailing protocols, used for email access
  • FTP (File Transfer Protocol) – Used for the transmission of files over networks
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11
Q

Describe the structure of the Internet

A
  • A global network of interconnected networks
  • Allows computers on opposite sides of the globe to communicate with each other
  • Continents are connected to each other using large international backbone cables. Many of these pass underwater
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12
Q

What is the The TCP/IP Stack

A

The Transmission Control Protocal / Internet Protocal is a group of protocols that work together specifiying how packets should be routed across a network

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13
Q

What are the the four layers of the TCP/IP stack

A
  • Application Layer
  • Transport Layer
  • Network Layer
  • Link Layer
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14
Q

What are the Advantages of Layering

A
  • Reducing a complex problem into smaller sub-problems
  • Devices can be manufactured to operate at a particular layer
  • Products from different vendors will work together
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15
Q

What is the function of the application layer during data transmission

A

Specifies what protocol needs to be used in order to relate the application that’s being sent

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16
Q

What is the function of the transport layer during data transmission

A
  • Establish an end-to-end connection between the source and recipient computer
  • Splits up data into packets
  • Adds to each packet: their packet number, total number of packets and port number
    *
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17
Q

What is the function of the network layer during data transmission

A
  • Adds source and destination IP addresses
  • Routers operate on the network layer and the router uses the IP to find out where the packets are heading
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18
Q

What is the function of the link layer during data transmission

A
  • Establishes the connection between the network devices
  • Adds the MAC address identifying the Network Interface Cards of the source and destination computers
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19
Q

What does the application layer do when it recieves data

A

Presents the data in the form it was sent using the protocal to see how the data needs to be presented (web page, image ect.)

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20
Q

What does the transport layer do when it recieves data

A

Reassembles the packets

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21
Q

What does the network layer do when it recieves data

A

Removes the IP addresses

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22
Q

What does the link layer do when it recieves data

A

Removes the MAC addresses

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23
Q

What are the Protocals used on each layer of the TCP / IP Stack

A
  • Application - HTTP, FTP, IMAP, SMTP
  • Transport - TCP, UDP
  • Network - IP
  • Link - Ethernet, 4G, 3G, Wi-Fi
24
Q

What is a Media Access Control (MAC) Address

A

Fixed serial number of a device, unique to a specific Network Interface Card (NIC)

25
Q

Why do we need both a MAC address and an IP address

A
  • Communication between two devices on the same local area network only requires the Link layer so uses the MAC addresses
  • Communications between two devices on differenet networks requires both the network layer (which uses the IP address) and the Link layer which uses the MAC address)
  • In practise communciation on modern LANs makes uses of the IP address as it treats LANs as if they were WANs
26
Q

What is a Local Area Network (LAN)

A

A network spread over a small geographical area, all the equipment is owned by the business / individual

27
Q

What is a Wider Area Network (WAN)

A

A network spread over a large geographical area, that typically requires extra hardware owned by a third party

28
Q

What is DNS (Domain Name System)

A

The domain name system (DNS) is the system used to name and organise internet resources

29
Q

What is the URL

A

Uniform Resource Locator

30
Q

How is a DNS (Domain Name System) organised

A
  • It is a hierarchy, in which each smaller domain is separated from the larger domain by a full stop
  • TLD stands for Top Level Domain, and 2LD stands for 2nd Level Domain
31
Q

Why do we use DNS (Domain Name System)

A
  • Domain names are much easier to remember than IP addresses
  • The role of the domain name system server (DNS server) is to translate these domain names into IP addresses when we wish to access a website
32
Q

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

A
  • DNS is used to find IP corresponding to URL
  • Request sent to local DNS
  • 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 next level of the heirarchy
  • The IP address is returned back up to the requesting client
  • Or an error if no IP address can be found.
33
Q

Describe the different sections of the Domain Name http//www.domainname.com/folder/subfolder/webpage.html#element

A
  • http:// - protocol/method
  • www - Host
  • www.domainname.com - Fully Qualified Domain Name
  • Domainname.com - Website Domain Name
  • /folder/subfolder/webpage - Location
  • # element - Resource
34
Q

What are Data Packets

A

Segments of data

35
Q

What information do Data Packets contain

A

Header

  • Sender and the recipient’s IP addresses
  • Protocol being used
  • Order of the packets
  • Time To Live / Hop Limit
  • Payload - The raw data
36
Q

What are the two techniques used when networks exchange data

A
  • Circuit switching
  • Packet switching
37
Q

What is Circuit Switching

A
  • A method of communication where a direct link is created between two devices
  • This direct link is maintained for the duration of the entire conversation between devices
  • Circuit switching requires the two devices to transfer and receive data at the same rate
38
Q

What is Packet Switching

A
  • Data is split into chunks called packets which have labels including address being sent to and order
  • Each packet is sent on the most convenient / avoidable route meaning they may arrive in a different order to which they were sent
  • Once packets arrive at receiver they are reordered
39
Q

What are the Advantages and Disadvantages of Circuit Switching

A

Advantages

  • The data arrives in a logical order (quicker reconstruction)
  • This enables two uses to hold a call without delay in speech

Disadvantages

  • Bandwidth is wasted during periods of time where no data is sent
  • The devices must transfer and receive data at the same rate
40
Q

What are the Advantages and Disadvantages of Packet Switching

A

Advantages

  • There are multiple methods to ensure data arrives (check Checksum and Cyclic Redundancy Check)
  • There is more than one method of getting to the other devices, so if one path breaks you can use another
  • You can transfer packets over very large networks to allow communication globally.

Disadvantages

  • Time is spent deconstructing and reconstructing the data packets.
41
Q

What is the purpose of a Firewall

A

Prevent unauthorised access to a network

42
Q

What is a Firewall made up of

A
  • Two network interface cards (NICs)
  • Firewall software
43
Q

How does a Firewall work

A
  • The two network interface cards (NICs), sit in-between the user and their internet connection.
  • The firewall passes packets between these two NICs and compares them against a set of rules (packet filters) set by the firewall software
  • It then performs packet filtering / static filtering
44
Q

How does packet filtering / static filtering work

A

It looks at the source IP and destination IP and then limits network access in accordance with administrator rules and policies

45
Q

What happens when a Firewall denies access

A
  • The packet is dropped
  • The packet is rejected which sends an alert to the sender to notify them of the error
46
Q

What is a proxy

A

A web server that acts as an intermediary, collecting and sending data on behalf of the user

47
Q

What are the Advantages of a using a Proxy Server

A
  • Allows user to remain anonymous
  • Data can be cached making it faster to load
  • Reduce the web traffic
  • Can be used by administrators to prevent access to sensitive or irrelevant information at work or at school
48
Q

What is Encryption

A

A way of keeping data secure when transmitting over the Internet

49
Q

What is the Function of a Network Interference Card (NICs)

A
  • It is card required to connect a device to a network
  • Assigns a unique Media Access Control (MAC) address to each device
50
Q

What is the Function of a Switch

A
  • Joins devices nodes together on the LAN
  • Inspects packets to find recipient MAC addresses
  • Directs the flow of packets across the network
51
Q

What is the Function of a WAP (Wireless Access Point)

A
  • Allow devices to connect to a network wirelessly
  • More commonly used to connect devices to a router which can allow internet access
52
Q

What is the Function of a Router

A
  • They route packets of data across networks
  • A router uses the destination IP address to find out where the packets are heading
53
Q

What is the Function of a Gateway

A
  • Used when protocols aren’t the same between networks
  • Connnects two networks and translates protocols so that both networks have the same protocols
54
Q

What is Client-Server Networking

A
  • Client-Server networks has clients computers connected to a server
  • The server provides access to all resources
  • The server holds all of the important data and has extra processing power
55
Q

What is Peer-to-Peer Networking

A
  • 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
  • This network is used in piracy, since it’s almost impossible to trace the origin of files
56
Q

What are the Advantages and Disadvantages of Client-Server Networks

A

Advantages

  • More secure as data is stored in one location
  • Central backups are carried out so there is no need for individual backups
  • Easier to manage users

Disadvantages

  • Relatively expensive to set up
  • Trained staff are required
57
Q

What are the Advantages and Disadvantages of Peer-to-Peer Networks

A

Advantages

  • Easy to share resources
  • Easy to maintain
  • Not dependent on a central server and its connection to the Internet
  • Specialist staff and hardware are not required

Disadvantages

  • Impossible to trace the origin of files
  • Backups must be performed separately
  • Poorer security
  • This type of network could contribute towards piracy

Computer Science Paper 1 (16 decks)

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