OSI Reference Model

OSI Reference Model

OSI stands for Open Systems Interconnection. OSI model consist of  seven layers.Each and every layer have equal importance.
Physical Layer : This layer is bottom layer.In this layer data in form of bits.Basic functionality of this layer is to  limit data rate i.e bits per second,synchronisation at bit level with other deice,and also concerns with transmission mode (Simplex,half duplex,full duplex).

Data Link layer : This layer co-ordinate with network layer and physical layer.In this layer data in form of frames.Error controlling and handling easy done by this layer.Data link layer address is also know as MAC address or Physical address works on this layer.

Network Layer : The layer co-ordinate with transport layer and data link layer.Data is in form of packet in this layer.The main purpose of this layer is to deliver packet from source to destination using logical address i.e IP address.

Transport Layer : This layer provide assurance  to deliver message  in order as well as error control and flow control using windowing. TCP and UPD are working in transport layer.Transport layer breaks message in segments and gives sequence number.It provides reliable(TCP) and unreliable(UDP) connections.

Session Layer : This layer is use to maintain session among different application.The basic responsibility of this layer is dialog control and synchronisation.

Presentation Layer :  This layer is taking care of syntax and semantics of information exchanged between the different systems.It just represent information is such a ways that the another system can easily understand.

Application Layer : This layer actually work with application and various type of services like email,File transfer ,Directory services provided by it.