Network Protocols and the 4 Layer Model

• Protocol


  Accepted rules of communication so devices can be compatible and communicate reliably
• Protocols


  • Sets of rules for communication and enabling devices to communicate reliably
  • Standardized playing field where all devices agree to the same rules to communicate with any device worldwide
• Layers


  Levels of abstraction where each layer is responsible for different parts of the communication process
• Layers in TCP/IP protocol suite

  • Application layer
  • Transport layer
  • Network layer
  • Link layer
• Layers


  • Modular and distinct, can operate independently but together complete the communication process
  • Manageable self-contained parts, each with a very specific role
  • Allows for developing new protocols that need to work with the above and below layers
  • Increasing level of abstraction from link layer to application layer
• Decomposition is the general process of breaking down a complex process into manageable self-contained parts, each representing a layer
• Having self-contained layers means changing one layer won't affect the others as long as the input/output format remains the same
• At the application layer are web browsers, email clients etc. which are the furthest abstraction from the actual data transfers happening at the lower layers
• The communication process flows from the application layer down through the transport, network and link layers, and conversely when receiving data it flows up from the link layer to the application layer