What are Different protocol works at each of the Layer in OSI model?

OSI model

What are Different protocol works at each of the Layer in OSI model?

Application layer

• It’s responsible for providing an interface for the user to interact with application services or network services. Ex-Web browser (HTTP), Telnet
• A few examples of application layer protocols are the Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), and Domain Name System (DNS).

Presentation layer

• It’s responsible for defining a standard format to the data.
• The major functions described at this layer are: -
• Encoding-Decoding Ex- AVI-(video), WAV-(voice), JPEG (graphite), ASCII (text)
• Encryption-Decryption
• The presentation layer prepares data for the application layer. It defines how two devices should encode, encrypt, and compress data so it is received correctly on the other end. 
• The presentation layer takes any data transmitted by the application layer and prepares it for transmission over the session layer.

Session layer

• It’s responsible for establishing, maintaining, and terminating the sessions.
• Session ID is used to identify a session or interaction.
• Ex-Remote procedural call, Apple talk session protocol
• The session layer creates communication channels, called sessions, between devices. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends. 
• The session layer can also set checkpoints during a data transfer—if the session is interrupted, devices can resume data transfer from the last checkpoint.

Transport Layer

• It provides data delivery mechanism between applications in the network.
• Transport layer is the major function layerIn OSI layer
• Identifying service
• Multiplexing&De-multiplexing
• Segmentation, Error correction, flow control
• The transport layer takes data transferred in the session layer and breaks it into “segments” on the transmitting end. 
• It is responsible for reassembling the segments on the receiving end, turning it back into data that can be used by the session layer. 
• The transport layer carries out flow control, sending data at a rate that matches the connection speed of the receiving device, and error control, checking if data was received incorrectly and if not, requesting it again.

Transport layer protocols?

The protocols which takes care of data transport at transport layer are TCP/UDP

Different between TCP/UDP

 TCP UDP

Transmission Control Protocol →User datagram protocol

Connection Oriented  →Connection less

Support acknowledgements  →No support for acknowledgements

Reliable communication  →Unreliable communication

Protocol no.6  →Protocol no.17

Ex-HTTP, FTP, SMTP  →DNS, DHCP, TFTP

Network Layer

• It provides logical addressing path determination (routing)
• The protocols that work in this layer are: -Routed Protocol, Routing Protocol
• Routed Protocols→Used to carry user data between data.
• Routing Protocols→used performs path determinisation routing.
• The network layer has two main functions. One is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network. The network layer uses network addresses (typically Internet Protocol addresses) to route packets to a destination node.

Data link layer

• It provides communication with network layer.
• Mac (media access control) it provides reliable transit of data across a physical link.
• The data link layer establishes and terminates a connection between two physically-connected nodes on a network. It breaks up packets into frames and sends them from source to destination. This layer is composed of two parts—Logical Link Control (LLC), which identifies network protocols, performs error checking and synchronizes frames, and Media Access Control (MAC) which uses MAC addresses to connect devices and define permissions to transmit and receive data.

Physical layer

• It defines the electrical, mechanical functional specification for communication between the network devices. 
• The physical layer is responsible for the physical cable or wireless connection between network nodes. It defines the connector, the electrical cable or wireless technology connecting the devices, and is responsible for transmission of the raw data, which is simply a series of 0s and 1s, while taking care of bit rate control.