Osi

OSI model = Open Systems Interconnection model

The Open Systems Interconnection model (OSI model) is a conceptual model that characterises and standardises the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard communication protocols.

Schema

Layer	Name	Description
7	Application	The top layer (apart from layer 8, the user) is responsible for a wide area. Some examples are resource sharing, remote file access, remote printer access and e-mail amongst other. Protocols using layer 7 includes FTP, DNS, and HTTP.
6	Presentation	This layer is responsible for character code translation such as ASCII, Unicode, and EBCDIC. TLS and SSL protocols operate at this level.
5	Session	Layer 5 is responsible for session establishment, termination and maintenance of sessions. Here we find the NetBIOS protocol and L2TP tunneling protocol.
4	Transport	This layer is responsible for traffic control, session-multiplexing and segmenting messages. Two commonly used protocols are TCP and UDP.
3	Network	The network layer is responsible for routing network packages. The layer provides traffic control, local addressing, and fragmentation. The most used protocol is IP, ICMP, and IGMP
2	Data Link	This layer is responsible for link establishment, acknowledgment, error-checking to name a few. Protocols operating here are the 802.3 (Ethernet), ARP and LLDP (Link Layer Discovery Protocol).
1	Physical	This layer is responsible for transmission and reception of the physical medium. Protocols like DSL and USB use layer 1.