The application layer is the seventh layer (layer 7) of the seven-layer OSI model. The application layer is the OSI layer closest
to the end user. This layer interacts with software applications that implement a communication component. Application layer
functions typically include the following:
- Identifying communication partners
- Determining resource availability
- Synchronizing communication
It is important to understand that user applications do not reside in the application layer. It is those protocols that interact
with the end-user application that reside in this layer. The application layer provides services for user applications to employ.
For example, when you use your web browser, that actual software is an application running on the computer system. The web browser
application will interact with services and protocols provided by the application layer, such as the HTTP protocol.
Application Layer Protocols
Here are examples of some of the protocols that function within the application layer of the OSI model:
- BOOTP - IP configuration
- DHCP - IP configuration
- DNS - Name resolution
- FTP - File Transfer
- HTTP - File Transfer
- IMAP4 - Messaging
- POP3 - Messaging
- Telnet - Remote Data Transmission
- TFTP - File Transfer
- SMTP - Messaging
- SNMP - Network Management
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