Open System Interconnection (OSI) Essay Example | Topics and Well Written Essays - 1250 words

Open System Interconnection (OSI) - Essay Example The data transport or 'lower layers' of the OSI model handle data transport issues and are implemented in hardware and software. The lowest layer, the physical layer, is responsible for actually placing information on the medium. As a side note, most systems today use a modified version of this model; for example TCP/IP uses a 6-layer model. The OSI model is generic and is not a communication model -it makes no assumptions about programming language bindings, operating system bindings or application and user interface issues. Communications are implemented through protocols which are a formal set of rules and conventions that govern how computers exchange information over a network medium. A protocol implements the functions of one or more of the OSI layers. The table below describes the role of each of the 7 layers in greater detail: Responsible for activating, maintaining and deactivating the physical link between network objects. Network interface cards and interfaces on routers run at this level. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. When an application on Computer 1 sends dat... Provides error checking, error recovery and flow control. The transport protocols used on the Internet are TCP and UDP. 3 Network Layer Makes the upper layers independent of the data transmission, switching technologies, and topology of the network. Determines which path(s) in the network that data will be routed. This layer is very important to the design and configuration for internetworking. IP and routing protocols operate here. 2 Data Link Layer Provides reliable transfer across the physical links. Establishes the beginning and end of blocks of data (with synchronization when necessary) Reorder frames which are out of sequence [framing]; error detection and correction rate of data transmission [flow control]. It is subdivided into the logical Link Control (LLC) and Media Access Control (MAC) sub layers. Bridges and switches interface here. 1 Physical Layer Responsible for activating, maintaining and deactivating the physical link between network objects. Network interface cards and interfaces on routers run at this level. Physical layer specifications define characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. Physical layer implementations can be categorized as either LAN or WAN specifications. electrical optical mechanical When an application on Computer 1 sends data to Computer 2 that data passes through each layer of the OSI model on Computer 1 until it gets to the Physical layer. At that point it is transmitted on the physical medium (e.g. cabling) across to the Physical layer on Computer 2. The data then passes up through the Physical, Data, Network, Transport, Session, Presentation and