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OCR A Level Computer Science > 1.3.3 Networks > Flashcards

1.3.3 Networks Flashcards

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1
Q

1.3.3 A)
What is a network

A

two or more computers connected together with the ability to transmit data between each other

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2
Q

1.3.3 A)
types of networks

A

Local area network (LAN) and wide area network (WAN)

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3
Q

1.3.3 A)
What the char of WAN & LAN

A

when defining what either one of them don’t use the word network as its in the world:
for example use - A group of computer connected over a small geographical area

WAN - large geographical area, allow 4 comms between sites
- WAN uses 3rd party connections
- WAN less secure than LAN

LAN - small geographical area or a single site
-Lan uses connection owned by user
- more secure than Wan

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4
Q

1.3.3 A)
What are the two types of network topologys

A

Physical and logical topology

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5
Q

1.3.3 A)
Explain physical and logical topology

A

phy - physical layout of wires and components which form thge netywork (bus, star, mesh)
Logical - layout which shows how the data flow

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6
Q

1.3.3 A)
Explain physical bus topology, adv & disadv

A
  • all devices connected to backbone cable. ends plugged into a terminator ( see notes 4 diagram)
    A) inexpensive, no addition hardware
    D) if backbone cable fails entire network disconnects, more traffic means less performance, all computers see the data transmissions, security risk as all devices receive the data
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7
Q

1.3.3 A)
Explain physical star, adv & disadv

A
  • uses a central node (normally a switch), which directs data through mac address, unique to a device used to indenify each device on the network.
    A) consistent preformance even w/ heavy traffic, if one cable fails rest uneffected faster transmission than bus as no data colisions
    D) enpensive due to switch & cables if switch fails rest of network fails.
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8
Q

1.3.3 A)
Explain physical mesh star, adv & disadv

A
  • every node is connected to every other node, commonly found in wirsless tech
    A) no cable costs (if wireless), more nodes increases reliablity and speed. nodes automatically incorporated, no central switch inc speed
    D) wirless devices normally cost more, if they are wireded they need more wires makes it more expensive and maintaining network is difficult
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9
Q

1.3.3 A)
What is protocols

A

Set of rules that allow data transmission between devices

Protocols are the rules governing communication between hardware devices.

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10
Q

1.3.3 A)
Explaining protocols
HTTP/TCP/IP/IMAP/POP3/FTP

A

-hypertext transfer protocol, webpages rendering, encrypted version is https (s = secure)
-tcp/ip (transmisson control networks / internet protcol) networking protocol routing packets thorugh network
-POP3/IMAP (post office protocol 3/ internet message access protcol) mailing used for emails
-FTP (file transfer protocol ) used to transfer files over network
_

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11
Q

1.3.3 B)
Define internet

A

a network of networks which allows global communicaion between computers

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12
Q

1.3.3 B)
What does tcp and ip stand for

A

transmission control protocol and internet protocol

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13
Q

1.3.3 B)
What is the tcp/ip stack

A

a stack of network protcols that work together passing packets during communicatioms

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14
Q

1.3.3 B)
What are the stages of protcol layering in tcp/ip stack

A

Application layer
Transport layer
Network layer
Link layer

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15
Q

1.3.3 B)
What are the stages of protcol layering in tcp/ip stack
Explain application layer

A

top of the stack that specifies what protocol needs to be used

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16
Q

1.3.3 B)
What are the stages of protcol layering in tcp/ip stack
Explain transport layer

A
  • uses tcp to establish end-end connection, source and computer
  • splits data into packets lables w/ numbers, total number of packets the og data splits into ports and port number used for comm
  • if packet lost, request requests a retransmission of lost packets
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17
Q

1.3.3 B)
What are the stages of protcol layering in tcp/ip stack
Explain network layer

A

-adds sourve & destination ip address ( ip address + port number = socket address)
- routers operate on this layr, use ip address to forward packets
- sockets used to specify which device packets sent too and too the application being used.

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18
Q

1.3.3 B)
What are the stages of protcol layering in tcp/ip stack
Explain link layer

A

-connection between the network devices adds MAC address indentifying the network interface cards of sourve and reviceing computer
- on same network mac is address of recipent computer or router

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19
Q

1.3.3 B)
Why is the ip/tcp stack a stack ?

A

on the recipents computer these layers are looked from bottom to top. Once the destination has been reached mac address is removed by link layer. Ip address removed by network layer. transport layer removed port and reassembles the packets. finally app layer presents data to recipent in form it was requested in.

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20
Q

1.3.3 B)
The ip/tcp stack in order at the souce and at the recipents

A

Source :
file > app layer > transport layer > network layer > link layer
recipients :
link layer > network layer > transport layer > application layer > file

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21
Q

1.3.3 B)
Char of WAN

A

large geographical area, allow 4 comms between sites + normally needs extra tel communications hardward. Infustructure of wan owneed by third party

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22
Q

1.3.3 B)
Whats A DNS

A

Domin name system used to name and organise internet resourves. Its a hierarchy in which each smaller domina is seperatewd from the layer domin by a full stop. (leed.gov.uk)

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23
Q

1.3.3 B)
What does TLD and 2LD stand for in terms of dns

A

top level domain and 2nd level domain

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24
Q

1.3.3 B)
why is DNS used

A

Domina names easier to rememeber then ip address, role of dns is too translate these domains names into ip address

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25
Q

1.3.3 B)
What are data packets and what do they contain

A

are segments of data
containing - header, payload and trailer

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26
Q

1.3.3 B)
What are the properties of header in terms of data packets

A
  • sender/recipitant ip address - allows packets too be deliveed enabling recpent device to trace where packet came from
  • protcol being used - allows recipent computer to understand how it interprets the packet
  • order of packets
  • time to live/ hop limit - tells packet when to expire so doesnt travel forever
27
Q

1.3.3 B)
What are the properties of payload in terms of data packets

A

-raw data to be transmitted

28
Q

1.3.3 B)
What are the properties of trailer in terms of data packets

A

Checksum, or cyclic redundancy check - contains code to detect weather any error occured furing transmission

29
Q

1.3.3 B)
What are the two methods which networks exchange data:

A

Packet switching and circuit switching

30
Q

1.3.3 B)
What is packet switching

A

method of communication using packets across a network packets are spent across the most efficient route

Data is split into packets which have labels including address its being sent too and the order. Each packet is sent using the most coinvent route. This means they wont be sent in order. Once packets arrive can be re-ordered

At each node network destination is read and best route found

31
Q

1.3.3 B)
adv/ dadv of packet switching

A

A) multiple methodsm multiple routes if one breaks, allows for global communication, cannot be intercepted all at one location, eff use of bandwidth, if there is an error that part is identifed and retransmitted.
D) time spent re/decontructing packets, must wait for all packets to arrive

32
Q

1.3.3 B)
What is cirtuit switching

A

method of communication where a direct link created between two devices, direct link is maintained for the duration of entire convo requres two devices to transfer and revice datas at same rate

33
Q

1.3.3 B)
adv/dadv of circuit switching

A

A) data arrives in logical order = quick reconstruction, call w/o delay
D) Bandwidth waste when no data sent must be transfer / revieve @ = rate, switch may cause eletrical interferance and corrupt data, sections of network cantt be used used by other data till transmisson complete

34
Q

1.3.3 C)
What is a firewall

A

device designed to prevent unauthorised accress to a network consisting of two NIC between user and internet

35
Q

What’s a firewall

A

A software program or hardware device that restricts communication between a private network or device and an outside network

36
Q

1.3.3 C)
How does a firewall work

A

passes the packets through these two NIC comparing these against set of rules set by the firewall software.
The preconfigured rules are called packet filters.

37
Q

How does a firewall restrict communications

A

By using two NIC, data enters the first NIC and compares it too the rules of the network, traffic that matches rules passed out of the other NIC

38
Q

1.3.3 C)
How does packet filters / static filtering work

A

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

39
Q

1.3.3 C)
What happenes when packet doesnt follow the rules

A

packets can either be droppped or rejected.
rejectet packets sends an error elelert to sender. dropped packets dont.

40
Q

1.3.3 C)
What is encryption

A

a way to keep data secure when tranfering data makes data unreadable. en/dycrypting with a key (actual info on 1.3.1 A)

41
Q

1.3.3 C)
What is a proxie

A

acts as a intermedian collecting / sending data on behave of user

42
Q

1.3.3 C)
What are the benifits of using a proxie

A

-priveacy protected remain annonymus
-can cache frequently used things making websites load faster
- can reduce web traffic
- can be used by admins to prevent access to sensive or irreleveant info at skl or work

43
Q

1.3.3 D)
Whats a NIC

A

Network interface card, is a card required to connect a device too a network. assigns a unquie media access control accress (MAC ) to each device, MAC address is 48 bit coded into a device written as 12 digit hexadeciaml

44
Q

1.3.3 D)
Whats a switch

A

used to direct the flow of data across a network common in star topology

45
Q

1.3.3 D)
Whats a WAP

A

wirseless access point, allows device to connect to a network combinded with a router to enable internet access common in mesh

46
Q

1.3.3 D)
Whats a router

A

used to connect two + networks together allows for private home networks to connect too the internet

47
Q

1.3.3 D)
Whats a gateway

A

used when protcol are not the same between networks. IT translates procol so networks can communicate with eachother work by removing the header frokm packets b4 adding the data to packets using new packets

48
Q

1.3.3 E)
What are the two network architectures or models

A

Peer to peer & client sever

49
Q

1.3.3 E)
What is client-sever architecture

A

a network consiting of terminals known as client connected to a sever. A sever is a powerful central computer, holds all important recoures clients can request to use sever.

50
Q

1.3.3 E)
What is the adv / davs of client-sever architecture

A

A) more secure as stored in one place, central backups, data & resources shared between clients
D) relativly expensive, dependant on svr, trained staff needed for maintance

51
Q

1.3.3 E)
What is peer to peer archirecture

A

a network in which computers are connected to eachother. share files each device works as a client and a server. Requesting & providing data & rescources. used in piracy as impossible to track origin of file.

All computers have equal level of authority

52
Q

1.3.3 E)
What is the adv / davs of peer to peer architecture

A

A) cheaper, users can share resouces, ez to maintain, not dependant on central svr, no specialised staff needed
D) impossible to trace origin of file, seperate backups, poor security, may be difficult to locate resouces.

53
Q

Define backbone

A

Dedicated high transmission rate network connection between geographical locations

54
Q

Name the parts of the URL
http://www.mck.edu.au/subjects/IPT

A

http = protocol
www = resource is a webpage
mck = domain name
.edu top level domain
.au geographical domain
/ipt directory / file path / resource

55
Q

Switch vs hub

A

Hub sends data to all devices and switch sends depending on MAC address preventing collions

56
Q

Whats a switch

A

Switch connects computers together on a LAN it recieves and sends data depending on the MAC address

57
Q

Whats a hub

A

Hubs send data too all connected devices

58
Q

What is a bridge

A

provides a link between two LAN’s for example allowing for a student network to interact with an admin network.

59
Q

What is a standard

A

Standards are agreaments to enture hardware and software can work together.

60
Q

How does DNS work too translate an domain name into an IP

A

1) The user enters a web address or domain name into a browser
2)Browser sends message to network to find out which IP or network address the domain corresponds too
3) This is usually managed by the IPS
4) if the local ISP doesn’t have an answer it will then ask root name servers then top level domain server
5) A record of the domain is stored in cache so that next time it will be quicker

(Customers enter) domain name and this is sent to DNS servers.
• DNS servers map this domain to an IP address
• If the DNS server can’t resolve, it passes the request (recursively) to another DNS server.
• DNS Server sends the IP address to browser…
… so it can retrieve the website from server on which it is hosted.

61
Q

Why is having logical layer and physical layert separated good

A

Physical layer can be changed without having to rewrite logical layer

62
Q

What is a server

A

a device which provides a central point of control / access

63
Q

Why is server side checking importing

A

Prevent malicious code (SQL injection)
prevent non valid data input
client side processing can be modified and not shown on client side

64
Q
A

OCR A Level Computer Science (24 decks)

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