The Internet Flashcards
1
Q
What is the Internet?
A
- A network of interconnected computer networks which uses an end-to-end communication protocol
- Mostly a wired network, underwater cables connect different continents
2
Q
What are ISPs?
A
- Stands for Internet Service Provider
- Companies that provide customers with access to the Internet
- The largest ISPs / national ISPs provide internet to smaller regional ISPs
- Homes / businesses can buy access to the Internet from these
3
Q
What is a packet?
A
- Containers in which data is transmitted over networks
- Labelled with addresses for their sender and recipient
- Contain information intended for the recipient
4
Q
What are packet switching networks?
A
- Network in which data is sent in packets
5
Q
How do packet switching networks work?
A
- One message is split into multiple packets, each of which is sent to its recipient via the best possible route
- Packets are reassembled with other packets that form part of the same message by their recipient
- These pass through a number of routers before the destination, where the router determines where to send them by using the recipient address
- Every time a packet goes through a router, a hop occurs, only a finite nmber of hops can occur
- When a packet’s TTL expires, the packet is dropped
- The recipient notices a missing packet and requests for a retransmission
6
Q
What is TTL?
A
- Stands for Time to Live
- A packet’s TTL is a number that indicates how many hops the packet can partake in
- Reduced by one with each hop
7
Q
What are the components of a packet?
A
- Primary components of a packet:
- Sender’s address
- Receiver’s address
- Packet contents
- TTL
- Sequence number
8
Q
What is the sequence number of a packet?
A
- Contains the number of packets in a message and identifies a packet’s position in relation to others
9
Q
What are routers?
A
- Routers connect different networks
- They send packets to their recipient via the fastest route
- Hold tables with info relating to the fastest routes to certain devices
10
Q
What is a gateway?
A
- Gateways connect different networks
- Where two networks use different protocols, packets must be modified by a gateway so as to conform to both protocols
- Gateways strip away most of the packets details, leaving just the contents, then gives it a new send and receive address to comply with the new protocol
11
Q
What is a URL?
A
- Stands for Uniform Resource Locator
- Addresses assigned to files on the Internet
12
Q
What is the https:// part of a URL?
A
- The protocol being used to access a file
13
Q
What is the www part of a URL?
A
- Subdomain for the World Wide Web
14
Q
What is the bbc.co.uk part of a URL?
A
- Domain
15
Q
What is the .html part of a URL?
A
- The file’s extension
16
Q
What are the different TLDs available for use?
A
- Stands for Top Level Domain
- .com or .net or .org
17
Q
What is a domain name?
A
- Identifies an organisation or individual on the Internet
- Easy for humans to remember
18
Q
What is a FQDN?
A
- Stands for Fully Qualified Domain Name
- A domain that specifies an exact resource and always includes the server’s host name (e.g. www)
19
Q
What is an IP address?
A
- Stands for Internet Protocol address
- Assigned to every computer on the Internet and every device that communicates on a network
20
Q
What is a domain name server?
A
- Used to translate domain names into their corresponding IP addresses
- Stores a table of domain names and their corresponding IP addresses
- If a DNS doesn’t have a record of a domain, the request will be passed onto another DNS
21
Q
What is an internet registry?
A
- Organisations responsibe for the allocation of IP addresses
- Only 5 in operation, each serving a different geographical area
- When a new IP address is requested, a registry will looked for a previously allocated unused IP address rather than allocated a brand new IP address
22
Q
What is a firewall?
A
- These sit between a device and the Internet
- Regulates the packets that pass through them
- Either software or hardware
23
Q
What is packet filtering?
A
- Firewalls use this to accept or block packets based on their source IP address or the protocol in use
- Network admins can:
- Specify particular IP addresses or protocols
- Use automatic filtering software that can block suspicious packets
24
Q
What is stateful inspection?
A
- Examines the contents of a packet before deciding to allow it through the firewall
25
What is a proxy server?
- Servers that sit between a public and private network
- Manages every packet that passes between the two
- Firewalls can be said to act as proxy servers in this scenario
26
How do firewalls in proxy servers provide anonymity?
- When a device in a private network sends a packet through a firewall and into a public network
- The packets "sender" address is of the firewall, rather than the private IP address
- This provides the anonymity
27
What is symmetric encryption?
- Both the sender and receiver share the same private key
- This key is used to both encrypt and decrypt data sent
28
What is the issue of symmetric encryption?
- Before sending info, the sender and receiver participate in a key exchange
- If this same key is exchanged over a network, it is vulnerable to interception
29
What is asymmetric encryption?
- Each device has a pair of mathematically related keys
- One key is kept secret; the private key
- The other is shared on the Internet; the public key
- When a message is encrypted with the public key, ONLY the corresponding private key can decrypt it
- The recipient is the only one with the private key, the sender has the public key
30
What is a digital signature?
- Can be used alongside asymmetric encryption to:
- Verify the sender of the message
- Verify any message tampering/corruption during transmission
31
Describe the digital signature process in asymmetric encryption
- A digest of the message is created
- This is encrypted with the sender's private key
- The encrypted digest is appended to the message
- The message and appended digest are encrypted with the recipient's public key
- When the message is received, the recipient:
- Decrypts the message using their private key
- Decrypts the digest using the sender's public key
- Carry out the same digest algorithm on the message
- Check whether their result matches the now decrypted digest
32
What is a digital certificate?
- Verifies ownership of a key pair used in asymmetric encryption
- Can be used to check that a fake key pair isn't being used by an imposter
- Issued by certificate authorities, with the files containing the owners details, public key, and the digital signature of the CA
33
What is a worm?
- Piece of malicious software that can self-replicate between computers
- Either within a network or by users downloading and running malicious files
34
What is a trojan?
- A type of malware that is disguised as a benign file
- Users can be tricking into opening it
- Spread as email attachments or downloaded from malicious websites
35
What is a virus?
- Requires a host file in which to reside
- Files are usually executable files
- Can lie dormant until their host file is opened
- Spread between computers over private networks or the Internet
36
What precautions can be taken to avoid malware?
- Good code quality, as malware exploits bugs in code
- Antivirus software
- Train employees the risks of opening suspicious files/attachments
37
What is TCP/IP?
- Stands for Transmission Control Protocol / Internet Protocol
- Used in all parts of the Internet to enable communication between devices
- Formed from four distinct layers that form the TCP/IP stack:
- Application
- Transport
- Network
- Link
38
What is the role of the application layer of the TCP/IP stack?
- Selects and uses the correct protocol to transmit data
- Interacts with the user with application software
39
What is the role of the transport layer of the TCP/IP stack?
- Establishes a virtual path between the sender and receiver
- Splits the transmission into packets
- Each packet has a sequence number
- Also contains a port number which identifies the protocol
40
What is the role of the network layer of the TCP/IP stack?
- Provides the correct IP addresses for each packet's source and destination
- Routers work within the network layer, using the IP addresses on a packet to send it to its destination
41
What is the role of the link layer of the TCP/IP stack?
- Controls physical connections between pieces of hardware in a network
- Adds MAC addresses to packets that are received from the network layer
- These identify the hardware to where a packet should be sent
- These change with every hop through a network
42
What happens when a packet has been received?
- It is stripped of extra info by reversing the stack
- The link layer removes MAC addresses
- The network layer removes IP addresses
- The transport layer uses the packet's port number to determine the correct application to send the packet, but also uses the sequence number
- The application layer receives the packets and displays the info to the user
43
What two parts are IP addresses split into?
- A network identifier (computers in the same network share these)
- A host identifier
44
What is a subnet?
- When networks are divided into smaller networks, subnets
- These have different network identifiers
45
How is a network identifier found?
- It can be determined with a subnet mask
- To find it:
- Convert its IP address and subnet mask into binary
- Perform an AND on both numbers
- Convert to decimal
46
What are the two types of IP address?
- Version four; IPv4
- Version six; IPv6
47
What are IPv4 addresses?
- Dotted quad numbers
- Consists of 4 parts that are separated by dots, each of which is assigned one byte
- Over 4 billion unique addresses, but are in short supply
48
Why were IPv6 addresses created?
- IPv4 were in short supply, and the number of devices on the Internet that require a routable IP address is increasing rapidly
49
What are IPv6 addresses?
- Formed of eight blocks separated by colons, each of which contains four hex characters
50
What is a routable and non-routable IP address?
- Routable is a public
- Non-routable is a private
-
51
Why do most homes share the same IP address?
- If every device that is connected to a network had its own IP address, there wouldn't be enough IP addresses to go around
52
What is DHCP?
- Stands for Dynamic Host Configuration Protocol
- The number of available private IPs within a private network is limited, DHCP assigns IPs to devices when they join a network, by using a pool of available IPs
- These are allocated for the duration, once a device leaves, the IP returns to the reallocation pool
53
What is NAT?
- Stands for Network Address Translation
- When a computer on a private network communicates with a device online, the device cant respond directly to the computer as the computers IP isn't globally unique
- NAT sends packets through the router which:
- Makes a record of the packet
- Replaces the private IP with its own routable IP
54
What is port forwarding?
- Used when a client communicates with a server that is connected to a private network
- The client sends packets to the public IP of the router belonging to the server's private network which contains the port number of the app on the server
- The packets are forwarded by the private router to the server using NAT
55
What are the steps for a client to connect to a database?
- Client-sever request made by client to web browser
- Web browser responds with the requested web page
- The file contains JavaScript which loads an API, which uses REST to enable the database server to be queried by the client using HTTP
- The database server responds by using JSON or XML
- The clients browser processes the JSON or XML and displays the response
56
What is XML?
- Stands for Extensible Markup Language
57
What is JSON?
- Stands for JavaScript Object Notation
58
Compare JSON with XML
- JSON is more compact, easier to read, easier to create and faster for computers to process
- XML is more flexible
59
What is a thin-client network?
- The majority of network's processing power belongs to servers
- These provide services and resources
60
What are the advantages of thin-client networking?
- Easy to add new clients
- Clients are cheap machines
- Software updates and security are managed from the server, allowing for greater control
61
What are the disadvantages of thin-client networking?
- Requires a powerful server which is expensive and requires expertise to set up and maintain
62
What is a thick-client network?
- The clients are powerful enough to provide their own processing power and services
- This removes the requirement for a server, although servers can still exist
63
What are the advantages of thick-client networking?
- No high costs and expertise needed as there is no server to set up and maintain
- Much quieter communication channels which reduces the likelihood of collisions compared to thin-client
64
What are the disadvantages of thick-client networking?
- Require more powerful clients than thin-client networks, so there is some cost in setting up
- Harder to maintain, no facility to issue updates and manage security from a central server
