Discuss OSI Reference model.
Answer:
The OSI Reference Model consists of seven layers as indicated below:
The main objectives of the OSI Reference Model are to:
* Allow manufacturers of different systems to interconnect equipment through a standard interfaces.
* Allow software and hardware to integrate well and be portable on different systems.
* Allow manufacturers of different systems to interconnect equipment through a standard interfaces.
* Allow software and hardware to integrate well and be portable on different systems.
The principles that were applied to arrive at the seven layers are as follows:
* Each layer should perform a well-defined function.
* The function of each layer should be chosen with an eye toward defining internationally standardized protocols.
* The layer boundaries should be chosen to minimize the information flow across the interfaces.
* The set of rules for communication between entities in a layer is called protocol for that layer.
The Physical Layer
* The Physical layer coordinates the function required to carry a bit (0s and 1s) stream over a physical medium.
* It defines electrical and mechanical specifications of cables, connectors and signaling options that physically link two nodes on a network.
The Data Link Layer
* The main task of the data link layer is to provide error free transmission.
* The data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer.
The Network Layer
* The network layer ensures that each packet travels from its sources and destination successfully and efficiently.
* The Network Layer deals with packets of data.
The Transport Layer
* The basic function of the transport layer is to accept data from the session layer, split it up into smaller units if need be, pass these to the network layer, and ensure that the pieces all arrive correctly at other end.
* Furthermore, all this must be done efficiently, and in a way that isolates the upper layers from the inevitable changes in the hardware technology. Transport layer provides location and media independent end-to-end data transfer service to session and upper layers.
The Session Layer
* The session layer allows users on different machines to establish sessions between them.
* A session allows ordinary data transport, as does the transport layer, but it also provides enhanced services useful in some applications.
* A session might be used to allow a user to log into a remote timesharing systems or to transfer a file between two machines.
The Presentation Layer
* The presentation layer is concerned with the syntax and semantics of the information transmitted.
* In order to make it possible for computers with different representations to communicate, the data structure to be exchanged can be defined in an abstract way, along with a standard encoding to be used “on the wire”. The presentation layer manages these abstract data structures and converts from the representation used inside the computer to the network standard representation and back.
The Application Layer
* The application layer is the OSI layer closest to the end user. It means that both the OSI application layer and the user interact directly with the software application.
* Application layer supports functions that control and supervise OSI application processes such as start/maintain/stop application, allocate/deallocate OSI resources, accounting, and check point and recovering.
* The function of each layer should be chosen with an eye toward defining internationally standardized protocols.
* The layer boundaries should be chosen to minimize the information flow across the interfaces.
* The set of rules for communication between entities in a layer is called protocol for that layer.
The Physical Layer
* The Physical layer coordinates the function required to carry a bit (0s and 1s) stream over a physical medium.
* It defines electrical and mechanical specifications of cables, connectors and signaling options that physically link two nodes on a network.
The Data Link Layer
* The main task of the data link layer is to provide error free transmission.
* The data link layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer.
The Network Layer
* The network layer ensures that each packet travels from its sources and destination successfully and efficiently.
* The Network Layer deals with packets of data.
The Transport Layer
* The basic function of the transport layer is to accept data from the session layer, split it up into smaller units if need be, pass these to the network layer, and ensure that the pieces all arrive correctly at other end.
* Furthermore, all this must be done efficiently, and in a way that isolates the upper layers from the inevitable changes in the hardware technology. Transport layer provides location and media independent end-to-end data transfer service to session and upper layers.
The Session Layer
* The session layer allows users on different machines to establish sessions between them.
* A session allows ordinary data transport, as does the transport layer, but it also provides enhanced services useful in some applications.
* A session might be used to allow a user to log into a remote timesharing systems or to transfer a file between two machines.
The Presentation Layer
* The presentation layer is concerned with the syntax and semantics of the information transmitted.
* In order to make it possible for computers with different representations to communicate, the data structure to be exchanged can be defined in an abstract way, along with a standard encoding to be used “on the wire”. The presentation layer manages these abstract data structures and converts from the representation used inside the computer to the network standard representation and back.
The Application Layer
* The application layer is the OSI layer closest to the end user. It means that both the OSI application layer and the user interact directly with the software application.
* Application layer supports functions that control and supervise OSI application processes such as start/maintain/stop application, allocate/deallocate OSI resources, accounting, and check point and recovering.
No comments:
Post a Comment