Networking: 7 layers

• The OSI Reference Model is the international standard for networked communications.
• The application layer is large and sometimes broken down into sub-layers. It handles authoring systems, mail, and user interfaces.
• The presentation layer is important for multimedia and hypermedia.
• Layers 2-5 are covered by protocol suites like TCP/IP or ATM.
• The physical layer makes use of copper wire, coax, or fiber.