OSI Reference model-functions of each layer

This article tells about the particular network functions performed by each layer of OSI seven layer reference model in data transmission starting from physical to application layer.

Physical Layer-This layer directly deals with physical media, transmits bits over a medium and is concerned with the electrical and mechanical specification of transmission media such as voltage level. Hubs and repeater work on physical layer.

Data Link Layer-This layer provides node to node delivery of data frames. Converts the message from upper layer into data frames and add a header containing the source and destination MAC addresses. It provides node to node error control and flow control. Switches and bridges work on this layer.

Network Layer-Routes data packets from one node to another using IP address. Layer 3 switches and routers work on this layer. IP (Internet Protocol) works on this layer.

Transport Layer-Provides reliable and transparent data transfer between end points. This layer provides end to end error control and flow control. Hides detailed network info from the upper layers in stack. TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) are protocols which are used on this layer.

Session Layer-Deals with connection establishment, data transfer and connection release or we can say maintains session. Provides communication through Simplex, Half and full duplex modes of data transfer.

Presentation Layer-deals with data representation and provides necessary conversion from one data format to another data format for example EBCDIC to ASCII. Also manages data compression, decompression, encryption and decryption.

Application Layer- Provides program to program communication. Application layer protocols include  HTTP, SMTP, Telnet,FTP.