• Star topology
  • Bus topology
    • Multiple switches chained together in a single line


  • PAN (Personal Area Network)
    • A network of personal devices
    • Smallest network
    • Phone --> computer
  • LAN (Local Area Network)
    • Small network (E.g. office, home, or building)
  • MAN (Metropolitan Area Network)
    • Group of LANs in the same geographical area
    • Sometimes called a Campus Area Network (CAN)
  • WAN (Wide Area Network)
    • Group of LANs spread out over a wide geographical area
    • The Internet is the largest WAN
  • WLAN (Wireless LAN)
    • Networks that transmit signals through air
    • Use radio waves


Network Address Translation (NAT)

  • Gateway device substitutes private IP with its own public IP
  • Uses a NAT table to do the translation
    • Different variations handle the translation
  • Translate one IP --> another IP
    • Private --> public
    • Public --> private
  • Designed to conserve public IP addresses needed by a network


  • Static/Source Network Address Translation (SNAT)
    • Gateway assigns same public IP to host each time it makes a request to access the Internet
  • Dynamic Network Address Translation (DNAT)
    • Gateway has pool of public addresses it assigns to local host when it makes a request to access the Internet
  • Port Address Translation (PAT)
    • Most popular form of NAT
    • Process of assigning TCP port number to each ongoing session between local host and Internet host
    • Which device and port should the traffic go to?

Ports and Sockets

  • Port numbers
    • Ensure data is transmitted to correct process among multiple processes running on the computer
    • Divided into three types:
      • Well-known ports --> 0 to 1023
      • Registered ports --> 1024 to 49151
      • Dynamic and private ports --> 49152 to 65535
  • Socket
    • Consists of host's IP and port number of an application running on the host
    • Example:

DMZ (Demilitarized Zone)

  • Physical or logical subnetwork
  • Adds additional layer of security for a LAN
  • Separates public facing resources from the rest of an organization's network
    • The rest of the network is firewalled

Computer Science