Unit 5 Networks and Web Technologies Flashcards
1
Q
What is the largest Network in the world?
A
The Internet
2
Q
What is the Internet?
A
A network of inter-connected networks
3
Q
What is the World Wide Web?
A
A collection of resources accessed via the Internet
4
Q
What is the main part of the Internet known as?
A
The backbone
5
Q
What is the Backbone of the Internet?
A
A set of dedicated connections that connect several large networks at various points on the globe. Each of these points are then connected to other regional networks, usually controlled by Internet Service Providers
6
Q
What does an ISP do?
A
Internet Service Providers
Provides access to individual end-users
7
Q
What is an Internet Address?
A
Each device on a network needs to be uniquely identified so that data can be sent to the correct destination, much like an address on a letter
8
Q
What is a URL stand for?
A
Uniform Resource Locator
9
Q
What does a URL do?
A
Specifies the means of accessing a resource across a network and its location
The protocol and the domain name of the resource together form the URL
10
Q
What is a DNS?
A
Domain Name System
Servers are dedicated computers with an index of domain names and their corresponding IP addresses
11
Q
How many DNS servers work together to catalogue every domain name
A
13
12
Q
Why do we not use IP addresses directly in a browser?
A
Because URLs are much more user friendly and easier to remember
13
Q
What could happen when the DNS Server does not have a record for a specific domain? (2)
A
- It could recursively handle the request so that it can eventually deliver an IP address or print an error message
- It could refer to a DNS server authoritative
14
Q
Why must Domain Names be unique?
A
Because otherwise the DNS request could be confused
15
Q
What are Internet Registries?
A
Organizations that control the allocation of domain names and IP addresses
16
Q
How many global Internet Registries are there?
A
5
17
Q
Who issues available Domain Names?
A
Internet Registries
18
Q
What is a LAN?
A
Local Area Network
Two or more computers connected together within a small geographical area
19
Q
What is a WAN?
A
Wide Area Network
A large network of information that is not tied to a single location
20
Q
What is a Network Topology?
A
The arrangement of the various computing devices which make up a computer network
21
Q
What is a Bus Topology?
A
An arrangement where nodes are connected in a daisy chain by a single central communications channel
22
Q
What are the advantages of a Bus Topology? (3)
A
- Inexpensive to set up
- Devices can be easily added
- Good for small networks
23
Q
How does a Bus Topology work? (5)
A
- All nodes are connected to a single backbone cable
- Each end of the backbone is connected to either a terminator or a computer which stops signals ‘bouncing back’
- Each node is passive
- Data is sent in one direction at a time only
- Only one computer can transmit successfully at any one time
24
Q
What the disadvantages of a Bus Topology? (4)
A
- Main cable is a point of failure
- Limited cable length
- Performance degrades with heavy use because of data collisions
- Poor security
25
What is a Star Topology?
An arrangement where a central node or hub provides a common connection point for all other nodes
26
What are the advantages of a Star Topology? (3)
- Easy to isolate problems
- Good performance
- More secure if a switch is used because data is only sent to recipient
27
How does a Star Topology work? (2)
- Computers are connected to a central node. This is often a switch
- A switch sends each communication to the specific computer it is intended for
28
What are the disadvantages of a Star Topology? (2)
- Can be expensive to set up because of the length of cable required
- Central device is point of failure
29
What is a Physical Topology?
How the devices are physically connected
30
What is a Logical Topology?
How the devices communicate across the physical topologies
31
What is Wifi?
A wireless networking technology providing high-speed Internet and network connections
32
What does WAP stand for?
Wireless network Access Point
33
What happens in Circuit Switching?
A communication connection is created between 2 endpoints for the duration of a phone call or transfer of data
34
What happens in Packet Switching?
Packets are often sent across networks that have multiple connections with multiple routes through a destination
35
What does a Router do?
Forwards data packets from one network to another
36
How to Routers work? (4)
- Each router stores data about the available routes to the destination node
- Looks up the destination IP address in its routing table to find the best router to forward the packet to
- Each transfer between routers is known as a hop
- Routers continue to forward the packet until it reaches its destination node
37
What is a Packet Split into? (3)
- Trailer
- Payload
- Header
38
What does a Packet Header Contain? (4)
- The recipient's address so that it can be directed appropriately across the network
- Senders address so that replies can be sent appropriately
- The packet number and overall number of packets in the transmission to assist in reassembling the data
- The Time To Live (TTL) or hop limit is also included
39
What does a Packet Trailer Contain?
Error checking components to verify the data received in the payload has not been corrupted on transfer
40
What is a Protocol?
A set of rules, or a formal description, of the format of a digital transmission. It will cover, for example, the size of the packets, the contents and format of the header, the error detection and correction procedure
41
When is a Gateway required?
When data is travelling from one network to another that use different protocols
42
Why are Protocols important?
They make sure that all data being transfered in consistent which is needed for communication to work
43
What is a TCP/IP Stack?
A set of rules used in turn, to format a message so it can be sent over a network. Each layer provides a specific function within the transmission of the message
44
What are the layers of a TCP/IP Stack? (4)
- Application layer
- Transport layer
- Internet layer
- Link layer
45
What is the Application Layer used for?
Providing services for applications that want to communicate across a network, often the Internet
46
Does the Application Layer determine how data is transmitted?
No, it only specifies the rules of what should be sent
47
How does the Transport Layer work? (4)
- Uses the Transmission Control Protocol (TCP) to establish an end‐to‐end connection with the recipient computer
- Splits data into packets and numbers them sequentially
- Adds port number to be used based on HTTP protocol
- At the receiving end this layer confirms that packets have been received and requests any missing packets be resent
48
How does the Internet Layer work? (3)
- Uses the Internet Protocol (IP) to address packets with the source and destination IP addresses
- A router forwards each packet towards an endpoint called a socket, defined by the combination of IP address and port number
- Each router uses a routing table to instruct the next hop
49
How does the Link Layer work?
- Operates across a physical connection
- Adds the MAC address of the physical NIC that packets should be sent to based on the destination IP address
- MAC addresses change with each hop
50
Using the TCP/IP Stack Levels, how is data received? (4)
- The Link Layer removes the MAC address from each packet and passes it to the Internet Layer
- The Internet Layer removes the IP address from each packet and passes it to the Transport Layer
- The Transport Layer removes the port number f from each packet, reassembles the packets in the correct order and passes them to the Application Layer
- The Application Layer presents the image data for the user in a browser
51
What does TCP/IP stand for?
Transmission Control Protocol/Internet Protocol
52
What does a MAC address do?
Media Access Control addresses
Uniquely identifies a physical device with a NIC
53
What does NIC stand for?
Network Interface Card
54
What is a Port used for?
Alerting a specific application to deal with data sent to a computer. They are used by protocols to specify what data is being sent
55
What is Port 20 typically used for?
File Transfer Protocol (FTP) DATA
56
What is Port 21 typically used for?
File Transfer Protocol (FTP) CONTROL
57
What is Port 22 typically used for?
Secure Shell (SSH) Remote login
58
What is Port 23 typically used for?
Telnet (unencrypted) Remote login
59
What is Port 25 typically used for?
Simple Mail Transfer Protocol (SMTP)
60
What is Port 80 and 8080 typically used for?
HyperText Transfer Protocol (HTTP)
61
What is Port 110 typically used for?
Post Office Protocol v3 (POP3)
62
What is Port 143 typically used for?
Interim Mail Access Protocol (IMAP)
63
What is Port 443 typically used for?
HyperText Transfer Protocol Secure (HTTPS)
64
What does FTP stand for?
File Transfer Protocol
65
What is File Transfer Protocol?
An application level protocol used to move files across a network. FTP uses the client-server model with separate data and control channels operating on ports 20 and 21
66
What are Mail Servers?
Dedicated computers that are responsible for storing email, providing access to clients and providing services to send emails
67
What are the protocols of Mail Servers? (3)
- SMTP
- POP3
- IMAP
68
What does the SMTP protocol of Mail Servers do?
Used to send emails and forward them between mail servers to their destination
69
What does the POP3 protocol of Mail Servers do?
Downloads email stored on a remote server to a local client (removed after download)
70
What does the IMAP protocol of Mail Servers do?
Manages emails on a sever so multiple clients can access the same email account in synchronicity
71
What is a Firewalll?
Software or hardware that controls access to and from a network
72
What happens in Packet Filtering?
Packets of data are inspected by the firewall to check which port they are attempting to access. If this traffic is to be allowed through, the port must be opened for the duration of the connection, otherwise the firewall will automatically reject it
73
What does a Proxy Server do?
Makes a web request on behalf of your own computer, hiding the true request IP addresses from the recipient
74
What are the purposes of a Proxy Server?
- Enables anonymous surfing
- Can be used to filter undesirable online content
- Logs user data with their requests
- Provides a cache of previously visited sites to speed access
75
What is Encryption?
The act of encoding a plaintext message so that it cannot be deciphered unless you have a numerical key to decrypt it
76
What is Malware?
Malicious software that annoys users or damages their data
77
What is a Worm?
A standalone program that does not require a user to run it in order for it to spread.
Worms exploit vulnerabilities in the destination system and spread automatically
78
What is a Trojan?
A programs that masquerades as innocuous or useful application. It cannot self-replicate and they often serve to open up back doors in your computer to the internet so that the processing power, internet bandwidth and data can be exploited remotely
79
What is Phishing?
Using an email to manipulate a victim into visiting a fake website and giving away personal information
80
When does Buffer Overflow Occur?
When a program accidentally writes data to a location too small to handle it
81
What is an SQL Injection?
When a malicious user enters SQL commands via online database forms to change the processing
82
What does HTML stand for?
Hyper Text Mark-up Language
83
What is HTML?
The language of the World Wide Web
HTML describes the content of Web Pages
84
What is the difference between HTML and CSS?
HTML is used to define the page content and structure
CSS are used to define page styles and appearance
85
What does CSS stand for?
Cascade Style Sheets
86
What can CSS be used to change? (4)
- The style of an entire website
- A single web page
- A section of a webpage define by a
tag or
- A single occurrence of an element, for example:
87
What are the ways that Styles can be applied to HTML content? (3)
- Inline styling to apply a unique style within an HTML element
- Internal, embedded styles defined within