What is OSI Model ?

OSI Model:-Its full form is Open Systems Interconnection model .its detail is given below

Physical Layer:- Physical Layer  provide connection between   devices.Physical layer convert data into signal its depend upon medium also convert data into bit stream.Physical Layer is two way or  one  way  transmission .Devices used in physical layer is Hub & Repeater.  

Data Link Layer :-It is also known as Layer 2.Its working on  physical Address or MAC Address.Its added header & footer with data. header known as Ethernet header and footer known as CRC footer.Ethernet Header contain source Mac address & destination Mac address.CRC footer is used for error checking.data link layer is  also known as frame .Devices used in Data link layer is  Bridge,Switch.Protocol used in this layer is  Ethernet,ARP,RARP&Token Ring.

Network Layer:- Network Layer select best path to deliver data.Network Layer added own header known as IP Header.IP header contain source & destination IP Address.Network layer data is known as Packet.Devices used in Network layer is Router Protocol used IP,IPX,DHCP,ICMP

Transport Layer : Transport Layer divide large amount of data into small unit is known as segmentation process.small amount of data is called segment.Transport layer added its own segment known as TCP Header.TCP header contain sequence port number .device used gateway and firewall.

Port  No: Port no is used to create virtual connection .

Source Port no: Source port no is system generated port address in the   range of  1024                                     to 65535.

Destination port  No:- Destination  port no is predefined .port address range is 0 to 1023

protocol used in  Transport layer is   TCP & UDP.

Session Layer:- It establish a logical connection  between source to destination and also synchronize a  dialog between  presentation layer  between two  host & manage their  exchange data. Protocols used NFS which port no is 973 and ASP

Presentation Layer:- Presentation layer translate data to common format also encrypt & decrypt  data  using MPEG (Motion Picture Expert  Group),JPEG(Joint Photograph Expert Group),MP3,Txt etc 

Application Layer :- When an application program run on application,the request is handover to application layer .Application layer interact with user directly.Protocol used in this layer is HTTP(80),FTP(21),SNMP(161),SMTP(25),POP3(110)TFTP(69),TELNET(23)