Networking

• Two primary protocols
  • TCP-IP
• Wired and wireless share many similarities
  • Same use of layer 3 network layer
• Network Calculators

Topologies

• Star topology
  • When all devices connect to one central network switch
• Bus topology
  • Multiple switches chained together in a single line

Networks

• 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

Addressing

• Data Link Layer: MAC address
• Network Layer: IP Address
• Transport Layer: Port numbers
• Application Layer:
  • FQDNs
  • Computer names
  • Host names

Network Address Translation (NAT)

• Gateway device substitutes private IP with its own public IP
  • When computers need access to other networks on the internet
• 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

Variations

• 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: 10.43.3.87:23

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