A

Applicalign

Pres antat i an

Sessiun

Transport

Network

Data link

Physical

Application

Prestation

Session

Transpon

NelworiĆ­

Data lin-k

Physical

OSI Layer Se rvi ce s

One OSI layer communicates with another layer to make use of the; services provided by the second I ayer. Thie sepvices prov^ed tuyv ad;acent layers pelp a gi ven OSI layer communicate with its pner layer in other computer systems. Three basic elements are involved in layer services: the service user, the service providen, and thm service access point (SAP).

In this context, the sesvice user is the OSI layer th at requests s ehvi ces fro m an adjesent OS I nayer. Tlhe s prvice pnovider is ahe OSI la yer ehat provides services to service users. OSI layers can provide services to multiple service users. The SAP is a conceptual location at which one OSI layer can request the services of another OSI layer.

a I sure 1 -a illhstfaVes how theee tha^e elements interact at the netwosk and data link layees.

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