Unit 10 - The Internet Flashcards
Define Internet
A network of inter-connected networks
Define World Wide Web
The set of resources that are available using the Internet
Define Internet Backbone
The principal data routes between interconnected networks and the internet
Define IP address
A unique identifier for a node connected to a network
Define FQDN
Fully Qualified Domain Name - a domain name that identifies the exact location of a web page in the WWW
Define URL
Uniform Resource Locator - a link that specifies the means of accessing a recourse and its location across a network
Define DNS
Domain Name System Server - dedicate computer (used as servers) with an index of domain names and their corresponding IP address
Define data packet
A block of data
Define circuit switching
Creating a communication connection between two end points for the duration of a phone call or transfer of data
Define latency
The time taken for a piece of data to arrive at the desired location
Define gateway
A networking device that connects two networks which are using different protocols
Define a firewall
Hardware or software that consists of a series of ports that control the traffic that pass through them
Define stateful inspection
Scanning payloads for malicious software before allowing them access to a network or device
Define proxy server
A server that acts on a devices behalf in order to keep the IP address of that client hidden when doing things such as using the internet
Define encryption
The act of encoding a plaintext message so that is cannot be deciphered unless you have a numerical key to decrypt it
Define symmetric encryption
Using the same key to decrypt the message as you used to encrypt the message and sending it across a network to the receiver
Define asymmetric encryption
Using two different keys to encrypt and decrypt a message so that a key does not have to be sent over a network
Define a digital signature
A method of verifying the integrity of a message
Define a worm
An individual program that does not need the user to spread through a computer and exploit vulnerabilities in the system
Define a trojan
A malicious piece of software that masquerades as something useful, it cannot self replicate but it can perform functions such as opening up back doors to your computer so the bandwidth and data can be exploited remotely
Define phishing
A communication that causes the user to visit a website and enter information that can then be exploited .e.g. bank details
Define SQL corruption
Entering commands into an SQL database to change processing or corrupt or access data
Define buffer overflow
When a program attempts to write data to a location that is too small and the data is placed into neighboring instruction space
Define TCP/IP stack
A set of rules used to format messages so that they can be sent across a network
Define MAC
Media Access Control - an address that uniquely identifies a physical device with a Wireless Network Interface Card
Define port
Alerts a device to deal with a piece of data to the computer
Define socket
An endpoint of a communication channel (often comprised of the IP address and the port)
Define SSH
Secure Shell - an encrypted protocol that allows secure communication between nodes across a network
Define unusable IP addresses
An IP address that is not used as they are reserved for specific purposes
Define NAT
Network Address Translation Service - a service provided by routers or other devices that allows devices with unusable IP addresses to communicate with the internet
Define subnet mask
Used on an IP address to identify the network identifier within the address
Define network identifier
The section of the IP address that identifies the network the nodes reside in
Define host identifier
The section of the IP address that identifies the specific nodes within the network
Define DCHP
Dynamic Host Configuration Protocol - a protocol that assigns dynamic IP addresses to devices within a network
Define a static IP address
An IP address that is assigned and does not change every time the same device connects to the network (as opposed to a dynamic IP address)
Define API
Application Programming Interface - a set of functions and protocols that a server provides to a client that details its functionality
Define WebSocket protocol
An API used to establish a persistent TCP socket connection
Define thick client
One that can do much of the processing independently of the server
Define thin client
A client that relies on the server for the majority of the processing a storage capacity
Define zero client
A type of thin client which downloads the latest configuration and OS version from the server each time the user switches on
Describe the internet backbone
A set of dedicated connection that are used to connect key large networks across the globe
Define ISP
Internet Service Provider - a company that provides subscribers with access to the internet
Which two parts make up a fully qualified domain name?
The domain name and the host name
Which three parts make up a URL?
The domain name, the host name and the resource to be accessed
What is the process when a computer wants to access a web page?
A request is made to the DNS server by the computer which provides the DNS server with the domain name. The DNS then returns the IP address the computer will use to access the web page.
How many global internet registries are there?
5
Why is packet switching better than circuit switching?
Packet switching allows communication channels to be shared
What happens during circuit switching?
A dedicated communications channel (route for packets) is made between two points for the duration of a communication, this channel cannot be shared
What are the three parts of a packet?
Header, payload and trailer
What is the size range for a payload?
500 to 1500 bytes
What does the trailer do?
It flags that it is the end of the packet and also includes checksum
What is a gateway?
A gateway occurs when a packet needs to be transferred between two networks with different protocols. The header is removed and then reapplied with the new protocols and correct format for the new network.
What device is a gateway often integrated with?
A router
What 4 things are included in the packet’s header?
Sender’s IP address, receiver’s IP address, protocol and packet number
What information do routers store?
Information about available routes to the destination node
Why is packet switching used?
Efficiency and reliability
How does a firewall work?
A firewall operates a series of ports which only lets certain types of data through
How does stateful inspection work?
Information is scanned for malicious software before it is let into the device
What programming concept does stateful inspection rely on and why?
Machine learning as the software will remember and record its decisions relating to certain pieces of infomation
What are the 4 main functions of a proxy server?
- Enables anonymous surfing
- Filters undesirable online content
- Logs user data and their requests
- Provides a cache of previously visited sites to speed up access
How does symmetric encryption work?
The sender encrypts the message with a key which it then sends to the receiver along with the message. The receiver uses the key to decrypt the message
What type of attack is symmetric encryption useless against?
‘Man in the middle’ attack
What does hybrid encryption involve?
The user sending a key to be used in symmetric encryption over a network using asymmetric encryption and then using symmetric encryption for the rest of the communications
How does asymmetric encryption work?
The sender encrypts the message uses a public key and the public key can only be decrypted with the private key.
How is a digital signature made?
- Irreversibly reducing the unencrypted message to produce a hash encrypting the hash using their private key
- The send bundles the digital signature with the message and encrypts the bundle using the recipient’s public key
- The recipient of the message uses their private key to decrypt the bundle
Describe the function of the application layer
Sending: ensures the data being sent is in the right format and employs the correct protocol .e.g. SMTP, FTP or HTTP
Receiving: presents the data for the user
Describe the function of the transport layer
Sending: splits the data into packets, numbers each packet and adds a port number
Receiving: confirms that packets have been received and requests any missing packet
What protocol does the transport layer use?
TCP (Transmission Control Protocol)
Describe the function of the network layer
Sending: uses IP (internet protocol) to address the packets and router will ensure the package gets to the socket (the end point)
Receiving: removes the IP address
What are routing tables?
Information stored in routers that allows the router to figure out the best route for information to take to reach the socket
Describe the function of the link layer
Sending: concerning itself with the physical connection, it adds the MAC address of the next WNIC to the packets (this changes after every hop)
Receiving: passes the MAC address to the network layer
What does FTP stand for and what ports does it use?
File Transfer Protocol, ports 20 and 21
What is SSH used for?
It is used to manage remote servers and other computers
Why is SSH good for managing remote servers?
It uses public key encryption which means that the data in the communication channel is protected
What is SSH tunnelling?
Become some functions (ports) may be blocked by firewalls .e.g. port 25 may be blocked to prevent someone from sending emails, the SSH uses a different port and this port can be used to pass other information through and overcome this problem
What is SMTP used for?
Sending or forwarding mail between mail servers and the destination
What is POP3 used for?
Downloading emails stored on a remote server to a local client which are then removed after download
What is IMAP used for?
Managing emails on a server so multiple clients can access the same email account at the same time
What 3 languages are web pages written in?
HTML, CSS or JavaScript
How are web pages broken down to be transferred?
HTML, CSS or JavaScript is broken down into their parts .e.g. headers and body and then they are broken down further and transferred according to TCP/IP protocols
Why are private, non-routable addresses used on LANs or private WANs?
It reduces the need for each device to have a unique IP address as two devices in different private networks can have the same IP address
Why can devices with private, non-routable addresses not access the internet directly?
Because there may be another device in a different network with the same IP address, if they both try to access the internet, it becomes confusing and the system will crash
Which piece of hardware do devices with private, non-routable IP addresses use to access the internet?
A device that can provide Network Address Translation (NAT) service/ gateway
What does NAT do?
When a device with a private, non-routable IP address send packets outside of the network, they will first send it to a server or gateway that provides NAT, there the server will remove the original IP address and port and replace it with its external IP address and port, it then stores the original IP address and the new one it generated in a table so when the packets return it can swap them again and route the packet to the correct device within the subnetwork
What is port forwarding?
Where publicly accessible servers are given a private, non-routable IP address to associate with a port. The public requests reach the external router of the private network using a the assigned port and data packets are automatically forwarded within the network to the correct device based on the non-routable IP address assigned to that port.
What are the two parts of an IPv4 address?
The network identifier and the host identifier
How can a network identifier be found within an IP address?
A subnet mask is used. It has all of the network identifier bits set to 1 and all the host identifier bits set to 0. By performing an AND operation between the subnet mask and the IP address it can isolate the network identifier.
Why are subnetworks created?
They are created by companies to split the number of available host IDs
What are the benefits of subnetworks?
- The broadcast domain is reduced which increases security
- The number of data collisions are reduced
- The number of available host IDs is increased so more devices can be connected to the network
Why can the host identifier and the network identifier be combined into one IP address?
Because they occupy complementary bits
Why is IPv6 favoured over IPv4?
IPv4 cannot provide enough IP addresses for all the devices in the world anymore
Why are static IP addresses uncommon?
Static IP addresses are easier to track and it means that fewer devices can connect to the network because the DHCP server cannot reclaim the IP address when the device disconnects
What does DHCP stand for?
Dynamic Host Configuration Protocol
What does DHCP do?
It assigns IP addresses and any other network configuration information to devices joining the network
Why is DHCP beneficial?
It means that not all addresses are being used at once and that, if a device leaves the network, its IP address can be assigned to a different one joining
What does CRUD stand for?
Create
Retrieve
Update
Delete
Define each element of CRUD
C: write a record to a database
R: retrieve a record from the database
U: amend a record
D: remove a record from a database
What is the flaw in the client having to request data from the server?
If too much time passes between the request being made and data being returned, the request will time out and the user will receive an error
What type of connection is a WebSocket connection?
Bidirectional and simultaneous
Why are WebSocket connections faster than others?
Packet sizes are reduced as they do not require headers
What is the dynamic between the devices in a client-server model?
The client requests services from the server which then returns data and information in response to the request
Which protocol is used for communication between servers and clients?
HTTP
What does HTTP stand for?
Hypertext Transfer Protocol
What are the four HTTP equivalents to CRUD that map to SQL commands?
Get
Post
Put
Delete
What are the advantages of WebSocket connections?
- Superfast and interactive connection
- Packet sizes reduced
- Usable for websites that require real time updates
- Server load reduce
- Saves bandwidth
- Lower running costs
- Few web servers required
What is REST and what does is stand for?
REpresentational State Transfer - an architectural style that determines how systems communicate with one another
What are JSON and XML used for?
They are formats for standardised data objects that the server and client can process
What are the advantages of JSON?
- Easier for humans to read, write and maintain
- More compact (less storage and quicker to transmit)
- Can be directly manipulated by JavaScript
What are the advantages of XML?
- Any data type is allowed
What are the disadvantages of JSON?
- Doesn’t work with all data type
What are the disadvantages of XML?
- Expansive use of tags which make it difficult to follow
List 6 different types of server
- File server
- Proxy server
- Print server
- Web server
- Application server
- Database server
What is the function of a file server?
Stores files externally to a device (these can be any type of computer file)
What is the function of a web server?
Provides access to web pages
How does a proxy server work?
It provides a gateway to each client to enable access to the Internet
What is the function of a print server?
Manages the printing of documents
What is the function of a database server?
Stores the content of databases and provides access to individual clients
What is the function of an application server?
Executes all of the procedures needed to run applications
Define a router
A networking device that forwards data packets between networks
Define an edge router
A router which links two networks
What are the two types of edge routers?
Subscriber routers and enterprise routers
Define enterprise router
A more powerful and expensive router
Define subscriber router
A smaller scale and lower cost router
Define a core router
A router which makes up part of the internet backbone
How do gateways work?
Removal of the packet header and reapplying it in a different format and protocols to allow the packet to travel between networks with different protocols
What is a hop limit?
The maximum number of hops a packet can make before it’s decided that it’s lost and is deleted
Why is a hop limit necessary?
It ensures that packets don’t just travel never-endingly between routers
Which section of a URL is not included in the FQDN?
The protocol .e.g. HTTP or HTTPS
Define TLD as part of a FQDN
Top level domain -
Define a non-routable IP address
An IP address that is used to identify devices on a private network
Define routable IP addresses
An IP address that is used to identify devices on a public network
If a subnet mask is not represented as a series of 1’s and 0’s what is the alternative format for its notation?
<IP> / <Number>
.e.g. 192.168.43.35 / 12
</Number></IP>
What can you use a subnet mask for?
To determine whether your device is on the same network as the one you are transmitting to
Why are dynamic IP addresses more beneficial than static IP addresses?
Dynamic IP addresses allow the DHCP server to reclaim the IP address each time the device disconnects meaning it can be assigned to a new device so more devices can connect to the network over time
