1.3.3: Networks

• Describe the bus topology

  • all terminals connected to a single cable
• advantages of bus topology

  • inexpensive
  • no need for additional hardware
• disadvantages of bus topology

  • entire network goes down in central cable fails
  • performance decreases with increased traffic
  • all computers can see data transmissions
• describe star topology

  • central node directs data flow
  • uses MAC address to identify devices
• advantages of star topology

  • consistent performance
  • only individual terminal affected if cable fails
  • fast data transmission
  • easy addition of new stations
  • no data collision
• disadvantages of star topology

  • expensive due to switch and cabling
  • entire network fails if central switch fails
• describe mesh topology

  • every node connected to every other node
  • commonly used in wireless networks
• advantages of mesh topology

  • no cabling costs for wireless networks
  • reliability and speed improve with more nodes
  • nodes automatically incorporated
  • no central switch, enhancing speed
• disadvantages of mesh topology

  • costly if wireless devices required
  • large number of cables required
  • challenging to maintain
• describe HTTP protocol

  • used for web page rendering
• describe TCP/IP protocol

  • networking protocol for routing packets through networks
• describe POP3

  • allows for email access to only that one computer
• describe IMAP protocol

  • email access from any device, anywhere
• describe FTP protocol

  • used for file transmission over networks
• what are the layers to the TCP/IP stack

  • application
  • transport
  • network
  • link
• describe the application layer

  • determines the protocol needed for the application being sent
• describe the transport layer

  • splits data into packets and labels them with packet numbers/ total packet count and port number
  • requests retransmission of lost packets
• describe the network layer

  • adds source and destination IP addresses
  • routers operate at this layer - forwarding packets based on IP addresses
  • specifies whihc device and application packets are sent to
• describe the link layer

  • connects network devices
  • adds MAC addresses, identifying network interface cards
  • uses recipient's MAC address if in same network
  • otherwise uses router's MAC address
• describe a LAN

  • local area network
  • limited geographical scope
  • typically used within a single building/campus
  • managed and owned by a single organisation
  • uses technologies such as ethernet
• describe a WAN

  • wide area network
  • connects LANs across cities/countries/continents
  • relies on telecommunication infrastructure
  • often involves leased lines, satellites...
• who typically owns WANs vs LANs

  WANs:

  • often owned by 3rd party company

  LANs:

  • usually owned and managed by organisation it serves
• describe a DNS

  • domain name server
  • used to name and organise internet resources
  • operates as a hierarchical structure
  • each domain separated by a full stop
  • serve as user-friendly alternative to IP addresses
  • easier for humans to remember/use
  • used to link to servers and resources across the internet
  • translates domain names into corresponding IP addresses
  • facilitates communication between client devices and internet servers
• Process of communicating with a DNS:

  1. User enters the URL of the website/web-page in a web browser.

  2. Browser checks computer’s DNS cache for a matching IP address.

  3. If not found, a request is sent to the ISP’s DNS resolver server.

  4. DNS resolver searches for the IP address; if found, it returns it to the originator.

  5. If not found, the request is passed to a higher level DNS.

  6. Once the IP address is found, the original DNS caches it for future use and returns it to the user.

  7. Browser uses the IP address to send the web page request to the web server.

  8. Web server retrieves the page and sends it to the originator for loading
• describe a data packet and the data attached to it

  • a segment of data transmitted over a network

  contains:

  • header
  • payload
  • trailer
• describe the header of a packet

  • contains sender and recipient IP addresses
  • specifies protocol being used
  • indicates order of packets
  • includes packet expiration to prevent infinite looping
• describe the payload on a data packet

  • contains raw data to be transmitted
• describe the trailer of a data packet

  • contains checksum
  • used to detect errors during transmission
• describe packet switch

  • method of communication in which data is transmitted in packets across a network
  • packets follow the most efficient route, potentially differing for each packet
• advantages to packet switching

  • checksums ensure data integrity
  • multiple routes between devices enabling redundancy in case of path failure
  • facilitates global communication over large networks
• disadvantages of packet switching

  • time spent on deconstructing and reconstructing data packets
  • reception of data requires waiting for all packets to arrive before processing
• describe circuit switching

  • communication method where a direct link is established between two devices for the entire duration of the conversation
  • require both devices to transfer and receive data at the same rate
• advantages of circuit switching

  • data arrives in a logical order = quicker data reconstruction
  • allows users to hold conversation without speech delay
• disadvantages of packet switching

  • bandwidth wasted during idle periods with no data transmission
  • requires synchronous data transfer between devices
  • use of switched can introduce electrical interference - potentially corrupting/destroying data
  • network sections are tied up during transmission - unavailable for other data until completion
• what are some common network security methods

  • firewalls
  • proxies
  • encryption
• describe a firewall

  • used to prevent unauthorised access to a network/ either within or outside of an organisation
  • consist of 2 NICs between user and internet
  • passes packets through NICs and compares to rules of firewall software
  • alerts sender if a packet is rejected
• describe a proxy server

  • acts as an intermediary (collecting and sending data on behalf of the user)

  benefits:

  • privacy protection
  • data caching
  • traffic reduction
  • access control
• describe encryption

  • used to keep data secure during transmission over the internet
  • It ensures that intercepted data remains unreadable to unauthorized parties.
  • Encryption involves both encrypting and decrypting data using specific keys.
• describe a NIC

  • A network interface card is necessary for connecting a device to a network.
  • Typically integrated into devices, it assigns a unique Media Access Control (MAC) address to each device.
  • The MAC address, a 48-bit value, is encoded into the device and represented as a twelve-digit hexadecimal number.
• describe a switch

  • used to direct flow of data across a network
  • only shares data with intended device in a network