391DP-2330/3030MAR 2005Ver. 2.1DP-2310/30109 General Network Information9.1. Network Protocol9.1.1. OSI Reference ModeHaving a model in mind helps you understand how the pieces of the network puzzle fit together. The mostcommonly used model is the Open System Interconnection (OSI) reference model. The OSI model, firstreleased in 1984 by the International Standards Organization (ISO), provides a useful structure for definingand describing the various processes underlying networking communications.The OSI model organizes communication protocols into seven layers. Layer 1, the Physical (Hardware)layer, consists of protocols that deal with how data is transferred across the transmission media. At theopposite end, Layer 7, the Application layer, interfaces the network services with the applications (software)in use on the computer. The five layers in between, Data Link, Network, Transport, Session andPresentation - perform intermediate communication tasks. In essence the OSI model is a framework thatdescribes how a function from one computer is transmitted to another computer on the network.7 ApplicationLayer Name Function Protocol6 Presentation5 Session4 Transport3 Network2 Datalink1 PhysicalNetBIOS, Windows, Sockets, etc...SMBSMTPFTPDNSHTTPTelnetetc...TCP/IPIPX/SPXNet BEUIApple Talketc...EthernetToken RingFDDIATMetc...TDITCP, UDPIP, IPX, etc...PPP...IP Address etc...MAC AddressRS-232C, X21...ODI Driver, NDIS DriverRepeaterHubNICSW HubRouterOSI Reference Model and Network Terms
