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OSI Reference Model

ISO / OSI / IOS ISO : International Organization for Standardization OSI : Open System Interconnect 　　　（Reference Model） IOS : Internetwork Operating System

The OSI Reference Model The ISO created and released the OSI reference model in 1984 to provide vendors with a set of standards to ensure greater compatibility and interoperability between various types of network technologies. The OSI reference model reduces complexity, standardizes interfaces, facilitates modular engineering, ensures interoperable technology, accelerates evolution, and simplifies teaching and learning.

The OSI Reference Model Application 7 Presentation 6 Reduces complexity Standardizes interfaces Facilitates modular engineering Ensures interoperable technology Accelerates evolution Simplifies teaching and learning Session 5 Transport 4 Lesson Aim <Enter lesson aim here.> Network 3 Data Link 2 Physical 1

The Seven Layers of the OSI Model Network Processes to Applications Provides network services to application processes (such as electronic mail, file transfer, and terminal emulation) Application 7 Presentation 6 Session 5 Transport 4 Lesson Aim <Enter lesson aim here.> Network 3 Data Link 2 Physical 1

The Seven Layers of the OSI Model Network Process to Applications Application 7 Data Representation Ensures data is readable by receiving system Formats data Structures data Negotiates data transfer syntax for application layer Presentation 6 Session 5 Transport 4 Lesson Aim <Enter lesson aim here.> Network 3 Data Link 2 Physical 1

The Seven Layers of the OSI Model Application 7 Network Process to Applications Presentation 6 Data Representation Interhost Communication Establishes, manages, and terminates sessions between applications Session 5 Transport 4 Lesson Aim <Enter lesson aim here.> Network 3 Data Link 2 Physical 1

The Seven Layers of the OSI Model Application 7 Network Process to Applications Presentation 6 Data Representation Session 5 Interhost Communication End-to-End Connections Handles transportation issues between hosts Ensures data transport reliability Establishes, maintains and terminates virtual circuits Provides reliability through fault detection and recovery information flow control Transport 4 Lesson Aim <Enter lesson aim here.> Network 3 Data Link 2 Physical 1

The Seven Layers of the OSI Model Application 7 Network Process to Applications Presentation 6 Data Representation Session 5 Interhost Communication Transport End-to-End Connections 4 Data Delivery Provides connectivity and path selection between two host systems Routes data packets Selects best path to deliver data Lesson Aim <Enter lesson aim here.> Network 3 Data Link 2 Physical 1

The Seven Layers of the OSI Model Application 7 Network Process to Applications Presentation 6 Data Representation Session 5 Interhost Communication Transport End-to-End Connections 4 Lesson Aim <Enter lesson aim here.> Network Data Delivery 3 Access to Media Defines how data is formatted for transmission and how access to the network is controlled Data Link 2 Physical 1

The Seven Layers of the OSI Model Application 7 Network Process to Applications Presentation 6 Data Representation Session 5 Interhost Communication Transport End-to-End Connections 4 Lesson Aim <Enter lesson aim here.> Network Data Delivery 3 Data Link Access to Media 2 Binary Transmission Defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link. Physical 1

Data Encapsulation Sender Application Presentation Session Transport User Data Application L7 HDR 7 User Data Presentation L6 HDR L7 HDR 6 User Data Lesson Aim <Enter lesson aim here.> Session L6 HDR L7 HDR 5 L5 HDR User Data Transport L4 HDR L5 HDR L6 HDR L7 HDR 4 User Data Network L3 HDR L4 HDR L5 HDR L6 HDR L7 HDR 3 User Data Data Link L2 HDR L3 HDR L4 HDR L5 HDR L6 HDR L7 HDR 2 User Data FCS Physical Bits 1 HDR = header

Data De-Encapsulation Receiver User Data Application L7 HDR 7 User Data Presentation L6 HDR L7 HDR 6 User Data Lesson Aim <Enter lesson aim here.> Session L6 HDR L7 HDR 5 L5 HDR User Data Transport L4 HDR L5 HDR L6 HDR L7 HDR 4 User Data Network L3 HDR L4 HDR L5 HDR L6 HDR L7 HDR 3 User Data Data Link L2 HDR L3 HDR L4 HDR L5 HDR L6 HDR L7 HDR 2 User Data FCS Physical Bits 1 HDR = header

Peer-to-Peer Communication Sender Receiver Application Application Presentation Presentation Session Session Lesson Aim <Enter lesson aim here.> Segments Transport Transport Packets Network Network Frames Data Link Data Link Bits Physical Physical Network

TCP/IP Model Application Transport Network Data Link Physical Lesson Aim <Enter lesson aim here.> Data Link Physical

TCP/IP Protocol Stack vs. OSI Model Application Layers Application Application Presentation Session Data Flow Layers Transport Transport Lesson Aim <Enter lesson aim here.> Internet Networks Network Network Access Data Link Physical

Summary The OSI reference model reduces complexity, standardizes interfaces, facilitates modular engineering, ensures interoperable technology, accelerates evolution, and simplifies teaching and learning. Each layer of the OSI model has a set of unique functions. The seven layers of the OSI model are the application, presentation, session, transport, network, data-link, and physical layers. Encapsulation is the process in which data is wrapped in a particular protocol header before network transit.