THE APPLICATION LAYER - LAYER 6
The Application layer provides three basic services to applications:
- It makes sure the resources needed to carry out a session are present.
- It matches the application to the appropriate communication protocol or service.
- It synchronizes the tgransmission of data between the application and its protocol.
The Application layer is used to support the following services:
- File services - store, move control access to, and retrieve files
- Print services - send data to local or network printers
- Message services - transfer text, graphics, audio, and video over a network
- Application services - process applications locally or through distributed processing
- Database services - allow a local computer to access network services
In addition, the Application layer advertises any services that are being offered and determines whether requests made by the client should be processed locally or remotely (through another network resource).
The Application layer services and protocols you should know are:
FTP (File Transfer Protocol)
E-mail clients
Web Browsers
Telnet
SNMP (Simple Network Management Protocol)
BBS (bulletin board system) services
EDI (Electronic Data Interchange) and other transaction services
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