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Computer Science > Unit 10 > Flashcards

Unit 10 Flashcards

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1
Q

How is the internet physically structered?

A

There are backbone cables connecting each continent by trans-continental leased lines fed across the sea beds

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2
Q

How is the internet provided to homes?

A

National internet service providers connect directly to the backbone and distributes the internet to smaller providers who provide it to induvidual homes and buisnesses

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3
Q

What is a URL?

A

The full address for an internet resource

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4
Q

What does a URL do?

A

It specifies the location of a resource on the internet including the name and often the file type so that a browser can go and request it from the website server

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5
Q

Why are there internet registrars?

A

They are needed to ensure that a particular domain name is only used by one orginisation and it holds all record of existing website names and the details of the domains which can be purchased

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6
Q

What are internet registries?

A

5 global organisations governed by ICANN (internet corportaion for assigned naems and numbers) which has a worldwide databse that holds all of the domain names currently issued to individuals and companies and their details

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7
Q

What do internet registaries do?

A

Allocate IP addresses and keep track of which addressses a domain name is associated with as part of the domain name system (DNS)

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8
Q

What is a domain name?

A

It identifies the area or domain that an Internet resource resides in, each domain name has at least one equivalent IP address

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9
Q

How are DNS’s structured?

A

As a hireachy or smaller domain sepearted by full stops.

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10
Q

What does the DNS do?

A

Catalogues all domain names and IP addresses in a series of global directories that domain name servers can access in order to find the correct IP address location for a resource

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11
Q

What happens when a webpage is requested?

A

A browser corresponding IP address from a local DNS, if that DNS doesnt have the correct IP address, the search is extended up the hierachy to another larger DNS database

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12
Q

What is a fully qualified domain name?

A

A fully qualified domain name is one that includes the host server

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13
Q

What is an IP address?

A

A unique address that is assigned to a network device

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14
Q

What does an IP address do?

A

It indicates where a packet has been sent from or to.

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15
Q

What are the two standard of IP addresses?

A

IPv4 and IPv6

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16
Q

What is the differece between IPv4 and IPv6?

A

IPv4 uses 32 bits, IPv6 uses 128 providing lots more combinations

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17
Q

How is IPv4 written?

A

4 8 bit numbers in dotted decimal notation.

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18
Q

What is the IP address 127.x.x.x used for?

A

Private non-routable addresses for diagnostics within local networks only

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19
Q

What is IP address of the network identifier?

A

x.x.x.0

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20
Q

What is the IP address of x.x.x.255?

A

Reservered as the broadcast address on that subnet where data is sent simultaneously to all subnetwork hosts

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21
Q

What is conventionally the default router address?

A

x.x.x.1

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22
Q

What is IPv4 made of?

A

It contains 2 parts, the network and host computer within that network

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23
Q

How many bits is the network part of the address?

A

32 bits

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24
Q

What is classful addressing?

A

Where a system of classes are used to define the size or proportion of the network and host identifiers within a 32 bit IP address.

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25
What is the different between Class A and Class C addresses?
Class A networks only use 7 bits for the network idetifiers, whereas class C had millions of networks with fewest hosts
26
What is the difference between classless and classful addressing?
Classless addresing means the split between host and network ID can be made anywhere, classful addressing means the split can only happen in a small number of fixed positions
27
What indicates the number of bits used for the network ID?
The number after the"/"
28
What are the pros of classless addressing?
This is more flexible and can help overcome there being a limited number of IP blocks in a classful system
29
What is a subnet mask?
It is used in conjunction with an IP address to identify two unique parts of the address, its number correspons to the number of bits used for the network ID.
30
How can a subnet mask be used with the IP address to identify the network?
The subnet mask can be ANDed with the IP address to seperate the network ID from the full IP address
31
What does a computer use the subnet mask for?
To figure out if the destination address is on the same network as the sender, if it is not the computer will send the data to a router
32
Why are subnetwork segments created?
They are created within larger IP networks so managment is eased and efficiency is improved by routing data through one segement only
33
Why is subnetting good?
Subnetting reduces the size of the broadcast domain which can improve security, speed, and reliabilty
34
How is a subnet ID created?
It is created by using the MSBs from the host ID section of the IP address
35
What must a public IP address be?
Globally unqiue and can be addressed by any computer in the world
36
What are examples of things that require a public IP address?
A web server or home internet router
37
Where can addresses be private?
Within local networks
38
What is a common IP block for class C private networks?
192.168.0.0 -> 192.168.255.255
39
What is a benefit of assigning private addresses?
Conserves the number of unique IPv4 address available
40
What is DCHP used for?
It is used to automatically assign a dynamic IP address from a pool of available address so that a computer can operate on a public network. It also provides the subnet mask and other automatic confiuration details alongside the IP address
41
What does dynamic addresing mean?
That the computer only has the IP address for the duration that it is online, and another computer can use it when its not online
42
Where is DCHP used?
On public and private networks
43
What is NAT (Network Address Translation) used for?
It is used to convert IP addresses as they pass between a public address space using a public IP address and a LAN with a private address spce
44
When is NAT required?
NAT is required to translate private IP addresses since they are not routable
45
How does NAT work?
An outgoing server request is made by a computer on a private address containing its own IP address and port number; the router then logs these as an entry in a translation table and swaps the packet IP with a unique port number; an incoming response is indentified by the port number and then is rebadged with the original workstations internal IP address and port number from the translation table
46
Why is NAT good?
It provides a solution to the lack of IPv4 address, it also security by creating an automatic firewall between internal and external networks
47
What is port forwarding?
Commonly a product of NAT when a public computer is trying to communicate with a server operating within a private network
48
Why is port forwarding needed?
Since there is no connectino to the server, the NAT needs to forward all incoming requests to a particular IP address and port
49
What is the TCP/IP protocol stack?
The transmission control protocol/ internet protocol protocl stack is a set of networking protocol that work together as four connecting layers
50
What are the layers of a TCP/IP stack?
Application layer, transport layer, network layer, and link layer
51
What is the application layer?
The application sits at the top of the stack and uses protocols relating to the application being used to transmit data over a network
52
Examples of protocols used on the application layer:
HTTP, POP3, FTP
53
What is the transport layer?
It uses TCP to establish end to end connection with the recipient computer after which the data is split into packets and labelled with: the total number of packets,the packet number, and port number
54
What does the network layer do?
It adds the source and destination IP addresses
55
What layer do routers use?
The network layer
56
What is a socket?
The IP address and the port which specifies which device the packet must be sent to and the application being used on that device
57
What is the link layer?
It is the physical connection between nodes and adds the MAC addresses identifying the NICs of the source and destination devices
58
Why is the link layer needed?
MAC addresses are needed to to find the correct piece of hardware once the packet finds the correct network
59
How often are MAC addresses changed?
They are chagned at each hop, the destination MAC address is always the next router
60
What happens when a packet is recieved in the TCP/IP protocol?
The MAC address is stripped by the link layer, IP addresses are moved by the network layers, the transport layer uses the port number to determine which application to pass the data to and then removes the port numer and reassebles them into the correct order, then the appliation layer is used to present the data to the user.
61
What is a MAC address?
A media access control address is a unique 12 digit hex code that is hardcoded on every NIC card
62
What does a port do?
It determines which application may deal with a data packet
63
What is the client port that a server request is returned to?
A temporary and arbitrary port number which is a security measure to ensure hackers do not know which ports are open on a client machine
64
What is server port 20?
FTP data
65
What is server port 21?
FTP control instructions
66
What is server port 23?
SSH remote login
67
What is server port 23?
Unecrypted Telnet remote login
68
What is server port 25?
SMTP
69
What is ports 80 and 8080?
HTTP
70
What is server port 110?
POP3
71
What is server port 143?
IMAP (interim mail acess protocol)
72
What is server port 443?
HTTPS
73
Why is FTP good?
It is very effcient at sending data across a network
74
What level does FTP work on?
FTP works as a high level protocol on the application layer
75
What does FTP do?
Using FTP, user actions can generate FTP commands automatically
76
When might FTP be used?
FTP sites may also be used by software companies using large updates of photographers uploading their lastest photos to a remote newspaper
77
What is packet switching?
Packet switching is a method of communicating packets of data across a network on which other similar communcations are happening simulateously
78
What is a packet?
Data that is to be transmitted across a network is broken down in more manageable chunks
79
What do packets contain?
Each packet contains a header and a payload which contains the body of data being sent, and sometimes a trailer
80
What does a trailer contain?
A checksum or cyclical redudancy check to detect transmission errors by creating and attatching a hash total calculated from the data in the packets
81
What does the header of a packet contain?
The senders and the recipeients IP addresses, the protocol being used in this packet and the number of packets in the sequence being sent, they also include the time to live (TTL) after which point data packet expires
82
What does the payload contain?
The payload of the packet contains the actual data being sent, and once received the packets are reassembled in the correct order
83
Why is packet switching so succesful?
Each packet can be sent a different way from one another, they will all go the fastest route
84
What are routers used for?
Routers are used to connect at least to networks, (often LANS and WANs or sometimes a LAN and its ISPs network)
85
What is a routers job?
The job of a router is to read the reciepients IP address in each packet and forward it onto the receipient via the next router, and so on until it reaches its destination
86
What is a routing algorithm?
Decides the best route can cause a bottleneck which becomes complicated
87
What happens when the protocols between the networks differ?
A gateway is used.
88
What does a gateway do?
All of the header data is stripped leaving only raw data and a new header is added in the format of the new network and the packet is fowarded on

Computer Science (8 decks)

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