OSI Refresh

9/25/20231 min read

Review of Major Concepts:

  • OSI model - Used to standardize different internet protocols and allow communication over networks

    • The OSI model has 7 level which i like to memorize by the mnemonic -- Please Do Not Touch Steve's Pet Alligator

      • 7. Application -- This is how you access an application (HTTP)

      • 6. Presentation -- How data is presented graphically (JPG)

      • 5. Session -- Establishing a connection (PPTP)

      • 4. Transport -- Actual transport of data from one computer to another (TCP, UDP)

      • 3. Network - Decides how send data over networks (Routers)

      • 2. Data Link -- Ensure data transfer to devices on your local network (Switches, Bridges)

      • 1. Physical -- Device that transports bits (NIC)

  • TCP/IP Model - Instructions on sending data over the internet

    • LITA (LLITAAA -- in respecto to OSI model layers)

      • Application

      • Transport

      • Internet

      • Link

  • Mac Address vs IP address

    • Mac address is given to a NIC (Layer 1 OSI) -- It is a physical address, can not be changed

      • Used in Layer 2 to communicate with other devices in a local network

    • IP address allow devices to communicate over a network (can be local or over the internet)

  • TCP vs UDP -- Both TCP and UDP are part of the Transport Layer and decided how data will be transported

    • TCP is connection oriented - Must establish a three way handshake

      • SYN, SYN-ACK, ACK

    • UDP is connectionless -- meaning that data packets can be lost, this is used when data needs to be transmitted quickly and can afford the data loss, used in gaming voice chat