The 7 layers at a glance Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer
Application LayerThe layer that lets you view the applications and dothings.Eg: Web Browser, Email browser
Presentation LayerPresents the data in the standard format.Eg: Things likely to be seen on a website- • Formats • Written Text HTML • Pictures JPEG • Video Clip MPEG • Sound Clip MP3This layer presents the data in its appropriate format.
Session LayerCreates a new session for each application and keeps each separate.Stuff being done at an instance:- • Checking emails. • Playing an online game. • Listening to an online radio. • Chatting on IM.For each of these activities a session is created, and maintained so that youremails do not come on the gaming screen and the radio start playing in theIM screen.
Transport LayerDetermines whether to send the data “RELIABLY”or “UNRELIABLY”.• Reliable means used when data integrity is of prime importance. Eg: Emails• Unreliable means used for real time applications when a small corruption in the data can be ignored rather than redelivery of the data packets.Defines the port numbers for each session.
Network LayerAssigns IP address of the source and destination PC.Searches and finds the best route to take the data from thesource to the destination.
DataLink LayerChecks for the MAC address of the PCs trying tocommunicate.Checks that the data being sent is error free.
Physical Layer Generates electrical pulses (0 and 1) of all the data to be sent through the cable.
Conclusion The source PC goes through these 7 layers to reach the destination PC. The destination PC receives the data via the same 7 layers beginning from Physical layer. Source PC Destination PC Application Layer Application Layer Presentation Layer Presentation Layer Session Layer Session Layer Transport Layer Transport Layer Network Layer Network Layer Data Link Layer Data Link Layer Physical Layer Physical Layer