- Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards.
- An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. (theoretical model for networks of all kinds)
- OSI reference model, drafted in late 1970s by ISO
- By 1983, the draft became ISO Standard 7498
- Common framework for developers and students of networking to work with and learn from
- Attempt to develop a working set of protocols and technologies based on the OSI model and to put those efforts into common use never materialized
THE OSI MODEL - Model’s foundation
- Networking can be separated into a series of related tasks
- Each task can be conceptualized as a single layer, of the communication process
- Reduces complexity of networked communications into series of interconnected tasks and activities
- “Divide and conquer” approach: relationship among tasks persists, but each can be handled separately, and its issues solved independently
- Reference models and standards enable interoperability among layers
Role of a Reference Model - Computer networking, computer compatibility, and networking features and functions can be daunting concepts to grasp
The interaction between layers in the OSI model - Communication between peer layers is “virtual”
- In reality, communications pass up and down the protocol stacks on both machines
- As data gets passed from layer to layer, it’s divided into data units appropriate for the layer
- Protocol data units (PDUs) are passed as a self-contained data structure from layer to layer
- Encapsulation process adds “headers” to allow successful delivery of each layer’s payload
- No layer can pass information directly to its peer counterpart except for the Physical layer
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