1-03-OSI.ppt
- 1. © 2003, Cisco Systems, Inc. All rights reserved.
- 2. © 2003, Cisco Systems, Inc. All rights reserved. 2 OSI Reference Model
- 3. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-3 ISO / OSI / IOS ISO : International Organization for Standardization OSI : Open System Interconnect （Reference Model） IOS : Internetwork Operating System
- 4. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-4 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.
- 5. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-5 The OSI Reference Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 • Reduces complexity • Standardizes interfaces • Facilitates modular engineering • Ensures interoperable technology • Accelerates evolution • Simplifies teaching and learning
- 6. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-6 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 Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1
- 7. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-7 The Seven Layers of the OSI Model Data Representation • Ensures data is readable by receiving system • Formats data • Structures data • Negotiates data transfer syntax for application layer Network Process to Applications Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1
- 8. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-8 The Seven Layers of the OSI Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 Interhost Communication • Establishes, manages, and terminates sessions between applications Network Process to Applications Data Representation
- 9. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-9 The Seven Layers of the OSI Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 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 Interhost Communication Network Process to Applications Data Representation
- 10. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-10 The Seven Layers of the OSI Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 Data Delivery • Provides connectivity and path selection between two host systems • Routes data packets • Selects best path to deliver data Network Process to Applications Data Representation End-to-End Connections Interhost Communication
- 11. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-11 The Seven Layers of the OSI Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 Access to Media • Defines how data is formatted for transmission and how access to the network is controlled Network Process to Applications Data Representation End-to-End Connections Data Delivery Interhost Communication
- 12. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-12 The Seven Layers of the OSI Model Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1 Binary Transmission • Defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link. Network Process to Applications Data Representation End-to-End Connections Data Delivery Access to Media Interhost Communication
- 13. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-13 Data Encapsulation HDR = header Sender Bits User Data User Data User Data User Data User Data User Data User Data L2 HDR L3 HDR L4 HDR L5 HDR L6 HDR L7 HDR FCS L7 HDR L7 HDR L7 HDR L7 HDR L7 HDR L6 HDR L6 HDR L6 HDR L6 HDR L5 HDR L5 HDR L5 HDR L4 HDR L4 HDR L3 HDR Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1
- 14. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-14 Data De-Encapsulation HDR = header Receiver Bits User Data User Data User Data User Data User Data User Data User Data L2 HDR L3 HDR L4 HDR L5 HDR L6 HDR L7 HDR FCS L7 HDR L7 HDR L7 HDR L7 HDR L7 HDR L6 HDR L6 HDR L6 HDR L6 HDR L5 HDR L5 HDR L5 HDR L4 HDR L4 HDR L3 HDR Application Presentation Session Transport Network Data Link Physical 7 6 5 4 3 2 1
- 15. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-15 Peer-to-Peer Communication Receiver Sender Network Bits Frames Packets Segments Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical
- 16. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-16 Application Transport Network Data Link TCP/IP Model Physical
- 17. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-17 TCP/IP Protocol Stack vs. OSI Model Application Presentation Session Transport Network Data Link Physical Application Transport Internet Network Access TCP/IP Protocol Stack OSI Model Networks Protocols Data Flow Layers Application Layers
- 18. © 2003, Cisco Systems, Inc. All rights reserved. INTRO v1.0a—1-18 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.