4: Networks and network security

• What are the types of networks?

  • LAN (local area network): covers a small geographical area, wired with fibre optic or wireless using wifi
  • WAN (wide area network): covers a large geographical area and can connect LANs, connected with telephone lines or optic cables or satellite links
• What are 3 advantages of networking?

  • users can share files
  • users can access their files from any computer on the network
  • communicate with other people
• What are 3 disadvantages of networking?

  • increased security risks to data
  • malware and viruses spread very easily between computers
  • computer may run slowly if there is a lot of data travelling on the network
• What is the internet?

  A global collection of interconnected networks- largest WAN
• What does the Domain name server do?

  • takes web addresses, which are easier for humans to remember, and convert them to IP addresses for routers
• What is an IP address?

  • unique address that identifies a device on the internet or local network - it allows a system to be recognised by other systems connected by the internet protocol
• What is a router and what does it do?

  • an essential hardware component of the internet
  • its main purpose is to connect multiple networks
  • it forwards info destined for either its own network or other networks
• Explain how data sent across networks is split up for transmission

  • the header of each packet contains various info including a source and a destination IP address
  • It also contains a sequence ID, which means packets that arrive out of order can be reassembled into the correct order once they arrive at the destination
• What is range and does wireless or wired connections have a longer range?

  • the maximum distance a transmission can travel before becoming degraded
  • wireless connections have a far shorter range than wired
  • bluetooth has a shorter range than wifi
  • copper cable has a shorter range than fibre optic
• What is speed in wired and wireless networks?

  • the transfer rate of data from source to destinations and is measured in bites per second
• What is latency and which is better wired or wireless?

  • the length of time it takes between a transmission being sent and received
  • latency is worse with wireless connections compared to wired
  • latency is worse with copper cable compared to fibre optic
• What is bandwidth in wired and wireless connections?

  • the maximum amount of data that can be transferred per second
  • the combination of network speed and bandwidth gives us network throughput
• Wired network performance advantages?

  • faster transfer speeds
  • easier to secure
  • connections and connection speeds tend to be more reliable
• Wired network performance disadvantages?

  • The need for a cable connection limits user location
  • lots of cables, connections, ports and other hardware needed
  • less convenient for sharing files as a physical connection is required
• Wireless network performance advantages?

  • users can access the network from anywhere within range
  • less complicated and disruptive to set up
  • easier to share files
• Wireless network performance disadvantages?

  • Transfer speeds tend to be slower
  • more complex to secure
  • less reliable and easily blocked by walls and other physical infrastructure
• network speeds are measured in bites per second - what are the conversions?

  • 1 Kbps = 1000 bits/sec
  • 1Mbps = 1000 Kbps = 1,000,000 bites/sec
  • 1 Gbps = 1000 Mbps = 1000 Kbps = 1,000,000,000 bites/sec
• what is data storage measured in?

  • bytes
  • 1 byte = 8 bites and 1KiB = 1024 bytes
• Formula to calculate the time to transmit a file?

  time = size of file (in bits)/network speed (in bits)
• what is a protocol?

  • set of rules that allows two devices to communicate
• What is Ethernet in terms of protocols?

  • family of related protocols providing the basics of communication over a LAN
• What is wifi in terms of protocols?

  • family of related protocols provided the basics of wireless communication
• What are the protocols for communication over LANs and WANs:

  • TCP (transmission control protocol)
  • provides an error free transmission between routers
  • IP (internet protocol)
  • routes packets across a wide area network
  • along with TCP it makes up the TCP/IP protocol stack
• What are the protocols for handling webpage requests?

  • HTTP (hypertext transfer protocol)
  • a client-server method of requesting and delivering HTML web pages
  • HTTPS (hypertext transfer protocol secure)
  • encryption and authentication for requesting and delivering HTML web pages
  • used when sensitive information needs to be transferred
• What is the protocol for file transfer?

  • FTP (file transfer protocol)
  • used for sending files between computers, usually on wide area network
• What are the email protocols?

  • SMTP (simple mail transfer protocol)
  • sends email to an email server
  • POP3 (post office protocol v3)
  • retrieves emails from a mail server. Removes it from server and transfers to your device
  • IMAP (internet message access protocol)
  • used by mail clients to manage remote mail boxes and retrieve email from a mail server
• What are the four layers of the TCP/IP model?

  • Application
  • Transport
  • Internet
  • Link
• What does the application layer in the TCP/IP model do?

  • encodes/decodes the message that can be understood by the sender and the recipient devices using protocols like HTTP, FTP and SMTP
• What does the transport layer in the TCP/IP model do?

  • breaks down the message into small pieces called packets
  • each packet is given a number, and the total number of packets
  • The recipient uses this information to assemble the packets in the correct order
  • also allows the recipient to see if there are any missing packets
• What does the internet layer in the TCP/IP model do?

  • adds the sender's IP address and that of the recipient
  • the network then knows where to send the message and where it has come from
• What does the link layer in the TCP/IP model do?

  • enables the physical transfer of packets between nodes on a network
• What are network topologies?

  • a networks topology is the arrangement in which all nodes on a network are connected together
• What is a bus topology?


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• What are the advantages of using a bus topology?

  • easy to install extra network devices
  • cheap to install as it doesn't require much cable
• What are the disadvantages of a bus topology?

  • if main cable fails then the whole network will fail
  • as more nodes are connected the performance of the network will become slower because of the data collisions
  • every node on the network receives all of the data sent on the network - security risk
• What is star topology?


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• What are the advantages of using a star topology?

  • each node is separately connected so the failure of one node doesn't affect any other nodes
  • new nodes can be added by connecting them to the switch
  • higher performance since a message is passed only to its intended recipient
• What are the disadvantages of using a star topology?

  • the whole network fails if the hub fails, since no node can communicate
  • requires alot of cable - in a large network this can be expensive
• What is a mesh topology?


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• What are the advantages of using a mesh topology?

  • messages can be received more quickly if the route to the intended recipient is short
  • messages should always get through as they have many possible routes they can travel along
  • multiple connections mean that each node can transmit to and receive from more than one node at the same time
  • new nodes can be added without interruption or interfering with other nodes