OSI Refrence Models

OSI Refrence Models

-Open System Interconnection
-Released In 1984
-IOS -Internetworking Operating System

1) Phsical Layer
2) Data Link Layer
3) Network Layer
4) Transport Layer- TCP/UDP
5) Session Layer- Mode Of Communication
6) Presentation Layer
7) Application Layer

Top 3
1)Appplication Layer
2)Presentation Layer
3)Session Layer

                      Top 3 layer defines how application within the end station will communicate each other and the bottom 4 layer defines how data is transmitted from end to end.Each of the layers have a protocol data unit (PDU)

• Application Layer deal with networking applications
• presentation layer responsible for presenting the data in the required format which may include

1. Code Formatting 2. Encryption 3. Compression

• Session layer deals with how communication will be done
• Transport layer are using two types of protocol TCP/UDP 
• TCP-Transmission Control Protocol, UDP- User Datagram Protocol       

                                        TCP is a connection oriented protocol and is reliable because we get acknowledgment when the data is reached the destination and if we don't get acknowledgment,the data will be retransmitted.

                  UDP is a connection less protocol and it is unreliable because we don't get acknowledgment                             

• Network Layer - packet filtering
• Data Link Layer - performs physical addressing
• Physical layer - The physical layer defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes