OSI MODEL

Open System Interconnection Model(OSM) developed by the International Standards Organization(ISO) which describes the flow of information from one computer to another.OSI model is also called ISO OSI reference model.

1. Physical Layer

• Physical layer is the first layer of the OSI model.
• In physical layer all the physical connectivity of a network,such as connectivity of devices using wires takes place.
• It converts data into bits and forward it to a data link layer.
• Devices work under this layer are : Hub,repeaters,cables etc.
• Datagrams at physical layer called bits.

2. Data Link Layer

• It is the second layer of the OSI model. It provides connection between hosts on same network.
• It converts bits into frames and forward it to the network layer.
• This layer is responsible for framing, physical addressing,flow control, error control and access control.
• Devices work under this layer are: Switch and Bridge and NIC.
• Protocols used under this layer are: PPP,PPTP etc.
• Datagram at data link layer called frames.

3. Network Layer

• It is the third layer of the OSI model.It provides connection between hosts on different network.

• It converts the frames into packets and forward it to the Transport layer.

• This layer is responsible for logical addressing, routing, etc.

• Devices works under this layer are router and brouter.

• Protocols used under this layer are: IPv4, IPv6 and ICMP.

• Datagram at Network Layer called packets.

4.TRANSPORT LAYER

• Transport layer is the forth layer of OSI model.

• It converts packets into segments and forward it to the session layer.

• This layer is responsible for segmentation, connection control, flow control and error control.

• Protocols works under this layer are: TCP and UDP.

• Datagram at Transport Layer called segments.

5.SESSION LAYER

• Session layer is the fifth layer of OSI model.

• It is responsible for dialog control and synchronization.

• This layer also controls duplexing, termination and restart.

• Protocols works under this layer are: TCP and RTP.

6.PRESENTATION LAYER

• Presentation layer is the sixth layer of OSI model.

• This layer is responsible for translation, encryption and compression.

• Protocol works under this layer is SSL.

7.APPLICATION LAYER

• Application layer is the last layer of OSI model.

• This is the only layer where user can directly interact with the data.

• This layer provides user interface, and supports services such as mail access, file transfer, browsing internet, remote desktop connection, etc.

• Protocol works under this layer are: FTP, TELNET, DHCP, HTTP, DNS, POP3, SMTP.