OSI or Open Systems Interconnection model consists of 7 Layers that describes how telecommunication or computing systems use to communicate or operate over a network. It was the first standard model for network communications and still widely used for network isolation and troubleshooting.
| Layers | Functions / Applications | Data Types | Examples |
| (7) Application | End User / Desktop -Mail Services -Directory Services -Network Virtual Terminal -File transfer access/management |
Data | HTTP,SMTP,FTP, SSH,DNS,Telnet, IMAP,POP3,LDAP, HTTPs,TFTP |
| (6) Presentation | Syntax/ Data Representation -Translation -Encryption/Decryption (plain to cipher text) -Compression |
Data | ASCII,JPEG,MPEG, GIF,EBDIC |
| (5) Session | Dialog Coordination -Session establishment/maintenance/ termination -Synchronization -Dialog Controllers |
Data | RPC, SQL,NFS, PAP,API,Sockets, Winsock,NetBIOS, SQL |
| (4) Transport | Transfer of Data -Segmentation & Reassembly -Service Point Addressing (port |
Segments | TCP, UDP |
| (3) Network | -Routing (route from source to destination) -Logical Addressing (IP address) |
Packets/ Datagram | Routers, IPv4, IPv6, IPSec,Appletalk, IGMP,ICMP |
| (2) Data Link | Node to Node Data Transfer 2 sub-layers: (a) Logical Link Control (LLC) (b) Media Access Control (MAC) -Framing (attach special bit patterns to start and end of frame – Physical Addressing (MAC) -Error Control -Flow Control -Access Control |
Frames | Switch,Bridge,PPP, SLIP,IEEE 802.3/802.2 ARP,CDP,FDDI,STP |
| (1) Physical | Physical (Electrical and Optical) Connection -Bit rate control (bps) -Bit synchronization -Transmission mode (simplex,half/full duplex) -Physical topologies (star,bus,mesh) |
Bits | Cables,Fiber,Coax,Hubs, Repeaters,Modems, Wireless |
[…] or computing systems use to communicate or operate over a network. For more info, refer to this 7 Layers of OSI Model: Functions and Examples and Layers of OSI Model […]