OSI Reference Model


Wikipedia says: “The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to their underlying internal structure and technology.” Click on the link below to view my PDF document.

OSIRefModel PDF

The PDF file link above will show you the seven layers of the OSI model.

  1. Application
  2. Presentation
  3. Session
  4. Transport
  5. Network
  6. Data Link
  7. Physical

Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer network. Go down to the physical and data link layer to get to the bits (physical layer) and frames (data link layer). The study of network topology recognizes eight basic topologies: point-to-point, bus, star, ring or circular, mesh, tree, hybrid, or daisy chain. Two basic categories of network topologies exist, physical topologies and logical topologies. The cabling layout used to link devices is the physical topology of the network.

The original twisted pair Ethernet using repeater hubs was a logical bus topology carried on a physical star topology. Ethernet is a widely deployed LAN technology.This technology was invented by Bob Metcalfe and D.R. Boggs in the year 1970. It was standardized in IEEE 802.3 in 1980.

Travelling higher up the seven layers of the OSI model we get into the discussion of having a centralized network, decentralized or distributed one.