Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Low-voltage differential signaling wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
Asynchronous Transfer Mode wikipedia , lookup
Computer network wikipedia , lookup
Deep packet inspection wikipedia , lookup
Network tap wikipedia , lookup
Airborne Networking wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Semester 1 Chapter 2 The O S I Model (Open System Interconnection) The OSI Model • The OSI model describes how information or data moves from one computer or end system through a network to another computer or end system. • The different layers refer to information flow. Why a Layered Network Model ? Application Reduces Complexity Presentation Standardizes Interfaces Session Facilitates Modular Engineering Transport Ensures Interoperable Technology Network Data Link Physical Accelerates Evolution Simplifies Teaching & Learning The purpose of the OSI model is to: • provide a standard way to describe how data travels on a network. • replace a number of competing standards with a single standard. • divide networks into seven layers and thus simplify the process. The OSI Model 7 Application Network processes to applications 6 Presentation Data Representation 5 Session 4 Transport End-to-end connections 3 Network Addresses and best path 2 Data Link Access to media 1 Physical Binary Transmission Interhost Communication The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical The application layer provides network services to user applications. For example, a word processing application is serviced by file transfer services at this layer. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer provides data representation and code formatting. It ensures that the data that arrives from the network can be used by the application, and it ensures that information sent by the application can be transmitted on the network. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical The Presentation layer is also said to be concerned with data structures and negotiation of data transfer syntax. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer establishes, maintains, and manages sessions between applications. It manages data exchange between presentation layer entities. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer segments and reassembles data into a data stream. This layer uses the TCP protocol. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer determines the best way to move data from one place to another. The router operates at this layer. This layer uses the Internet Protocol addressing scheme. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer provides physical transmission across the medium. It handles error notification, physical addressing, network topology, and flow control. This layer uses the Media Access Control (MAC) address. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer provides the electrical and functional specifications for activating and maintaining the physical link between systems. This layer uses the physical media like twisted pair, coaxial, and fiber-optic cable. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical This layer is also said to provide Data transmission across the network media. This is accomplished through the use of wires, connectors, and voltages. The OSI Model 7 Application 6 Presentation 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Host Layers Media Layers The OSI Model - Remembering order of the Layers: Application 7 • All Presentation 6 • People Session 5 • Seem Transport 4 • To Network 3 • Need Data Link 2 • Dr. Physical 1 • Pepper OSI model - Remembering order of the Layers (Bottom to top): • • • • • • • Please Do Not Tell Sales People Anything • • • • • • • 1 - Physical 2 - Data Link 3 - Network 4 - Transport 5 - Session 6 - Presentation 7 - Application Comparing the OSI & TCP/IP models • Similarities: • Both have layers • both have application layers, though they include very different services • both have comparable transport and network layers • packet-switched (not circuitswitched) technology is assumed Comparing the OSI & TCP/IP models • Differences - TCP/IP: • Combines the presentation and session layer issues into its application layer • Combines the OSI data link and physical layers into one layer (a.k.a. Network Interface) • Appears simpler because it has fewer layers • In the TCP/IP model, the Transport Layer is responsible for reliability, flow control, and error correction. Encapsulation • Encapsulation is the wrapping of data in a particular protocol header.