OSI Models

1. Physical Layer: 

Basically in this layer information gets from your computer is converted to digital signal ; information taken from strings and convert it to binary and transfer it into the lan. Basically you are transmitting 1 bit or multiple bit at a time. that is what physical layer is responsible for .

2.  Data Link Layer : 

• This is where NIC card just switch to NIC card(Just end to end)
• Frame error checking 
• Responsible for Information you are trying to send is going into correct order. 
• Frame acknowledgement 
• Here , CSMA/CD - Carrier Sense Multiple Access / Collision Detection means if it detects collision they basically listen to the line for certain amount of time and when they are free they start transmission again .  

3. Network Layer : - 

• Logical to physical 
• Traffic control 

4.Transport Layer : -

This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.
- Layer 4 Transport examples include SPX, TCP, UDP.

5. Session Layer :- 

This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.

- Layer 5 Session examples include NFS, NetBios names, RPC, SQL.

6. Presentation Layer :- 

This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer.

- Layer 6 Presentation examples include encryption, ASCII, EBCDIC, TIFF, GIF, PICT, JPEG, MPEG, MIDI.

7. Application Layer :- 

This layer supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely in the application level. Tiered application architectures are part of this layer.

- Layer 7 Application examples include WWW browsers, NFS, SNMP, Telnet, HTTP, FTP

Fig:OSI Models