Networks Flashcards
1.3.3
What is a network?
Name given to two or more computers connected with the ability to transmit data between each other
What is a LAN?
Local Area Network is a network that spreads over a small geographical area
What is a WAN?
Wide Area Network is a network that spreads over a large geographical area
What is a protocol?
Set of rules defining how two computers should communicate with each other ensuring secure data transmission and making sure they interpret data the same way
What is HTTP?
HyperText Transfer Protocol which is used for web page rendering
What is TCP/IP?
Transmission Control Protocol/ Internet Protocol used for routing packets through networks
What is POP3?
Post Office Protocol are mailing protocols used for email access
What is FTP?
File Transfer Protocol used for the transmission of files over networks
What is the internet?
A network of networks which allows computers on opposite sides of the globe to communicate with each other
What does the Application Layer do?
Interacts directly with software applications
Prepares data for transmission over the network by converting it into a format that can be sent and received over the network (known as encapsulation)
What does the Transport Layer do?
-Uses TCP to establish an end to end connection between the source and recipient computer
-Splits data up into packets and labels packets with packet number, total number the original packet was split up into and port number for communication
-If any packet gets lost, transport layer request retransmission of lost packets
What does the Internet Layer do?
-Receives packets from the transport layer
-It adds a header to each packet, including the sender’s IP address and the receiver’s IP address
-Responsible for routing each packet across the network using the IP addresses in the headers
What does the Link Layer do?
-Receives packets from the Internet layer
-Adds the MAC address of the sender and receiver to the data before transmission
-Translates the digital packets into an electrical, optical, or wireless signal that can be sent over the network
-Once the signal reaches the receiving end then translates it back into digital packets
For devices on the same network what is the destination MAC?
The MAC address of the first router that the packet will be sent to
What does each packet contain ?
-Payload(data)
-A header(With metadata and destination IP addresses)
-A footer(to signify end of packet)
What is the DNS?
Domain Name System is a directory of domain names and is used to translate human-readable domain names to numeric IP addresses that computers use
What are the benefits of DNS?
-Allows us to use easily remembered domain names instead if hard to remember IP addresses
-Handles mapping between domain names and IP addresses, relieving end users and system administrators from the task
What happens when you type a URL into a web browser?
(LONNNNGGGGG ASFFFF)
1️⃣User enters URL in a web browser
2️⃣ Computer checks cache for the IP address
3️⃣ Browser queries DNS resolver if IP is not cached
4️⃣ Resolver contacts DNS servers (Root → TLD → Authoritative)
5️⃣ Authoritative DNS server returns IP address
6️⃣ Browser sends request to web server at that IP
7️⃣ Web server responds with webpage data
8️⃣ Browser renders the webpage for the user
What are the advantages of LAN?
Centralised management
Security-Can secure devices with use of firewall, antivirus software
File Sharing-Allows users to share resources, files, and folders
What are the disadvantages of LAN?
If hardware fails network may not function properly
May be more prone to attacks
Accessing data and peripherals may be slow
Needs regular maintenance to ensure software up to date
Why are protocols divided into layers?
-Modular design meaning breaking complex process of networking into more manageable layers
-Interoperability-meaning that protocols that operate at network layer can be altered independently of application layer protocols
-Ease of updates-Changes can be made to one layer without affecting another making updates and improvements easier to implement
-Specialisation-Each layer can be specialised to preform its functions without worrying about specifics of other layers. Allows for more effective and efficient design
What information do headers contain?
Source IP address: identifies the sender of the packet
Destination IP address: identifies recipient
Sequence number: helps in reordering packets into original message
Protocol: identifies transport protocol
Packet Length: Indicates size of packet
Checksum: a value used for error checking
What is packet switching?
Network communication method that breaks down data into smaller packets and sends them separately along different routes and reassembles them at the destination
What are benefits of packet switching?
Efficient as packets can follow different paths using more of available bandwidth
More reliable as if a single packet fails only that packet needs to be sent not the whole stream
Lower cost due to shared network resources