OSI Model

• OSI - Open System Interconnection.
• OSI model created in 1984 by ISO.
• ISO - International Organization for Standardization.
• It is 7 layer architecture.

1. Physical Layer.
2. Data Link Layer.
3. Network Layer.
4. Transport Layer.
5. Session Layer.
6. Presentation Layer.
7. Application Layer.

Layer 1 – Physical Layer

• Physical layer is lowest layer of OSI model.
• It is responsible for actual physical connection between the devices.
• It converts the digital bits into electrical , radio ,or optical signal.
• It is responsible for transmitting individual bits from one node to the next.
• It establish, maintains and deactivates the physical layer
• Hub , Repeater, Modem and Cables are physical layer devices.

Layer 2 – Data Link Layer

• The Data Link layer responsible for node-to-node delivery of message.
• Directly connected two nodes.
• Data Link Layer transmit to MAC address.
• Data link layer is handled by the NIC.
• Switch and Bridge are data link layer devices.

Layer 3 – Network Layer

• The network layer works for the transmission of the data from one host to the other host.
• The sender and receiver IP addresses are placed in the header.
• Segment in the network layer is referred to as Packet.
• Network layer is implemented by networking devices such as router.

Layer 4 – Transport Layer

• Transport layer provides services to the application layer and take services from the network layer.
• End to end delivery of the complete message.
• This layer commonly used protocol included the Transmission Control Protocol and User Digram Protocol
• The main responsibility of the transport layer is to transfer data completely

Layer 5 – Session Layer

• This layer responsible for the establishment of connection , Maintenance of sessions and authentication.
• It is layer 3 in OSI model

Layer 6 – Presentation Layer

• The presentation layer mainly concerned with the syntax with the syntax and semantic of the information exchanged between to the system
• It is a data translator for a network
• The presentation layer also known as syntax layer

Layer 7 – Application Layer

• Application layer is connected with the specific type of application
• This layer allows users to interact with other software applications.
• Application Layer is basically not a function, but it performs application layer functions.