Application Layer

This graphic is taken from The Abdus Salam International Centre for Theoretical Physics.

Software Programs that tell the hardware of a computer how to perform tasks Programs that tell the hardware of a computer how to perform tasks Software can be divided into two general classes: systems software and applications software. Software can be divided into two general classes: systems software and applications software.

System software Systems software consists of programs that interact with the computer at a very basic level. Systems software consists of programs that interact with the computer at a very basic level. This includes operating systems, compilers, and utilities for managing computer resources. This includes operating systems, compilers, and utilities for managing computer resources.

Applications… Applications software (also called end-user programs) includes database programs, word processors, spreadsheets, games …. Applications software (also called end-user programs) includes database programs, word processors, spreadsheets, games …. Applications software sits on top of systems software because it is unable to run without the operating system and system utilities. Applications software sits on top of systems software because it is unable to run without the operating system and system utilities.

Application Layer The application layer is the seventh level of the seven layer OSI model. The application layer is the seventh level of the seven layer OSI model. It’s the “highest layer” of the OSI model. It’s the “highest layer” of the OSI model.

OSI: Layer 7 – Application Layer This is the layer at which This is the layer at which communication partners are identified communication partners are identified quality of service is identified quality of service is identified user authentication and privacy are considered user authentication and privacy are considered

Application Layer Review Everything at this layer is application- specific. Everything at this layer is application- specific. This layer provides application services for file transfers, , and other network software services. This layer provides application services for file transfers, , and other network software services.

Application Layer Protocols: The Hyper Text Transfer Protocol, or HTTP, is the most widely used Application layer protocol in the world today. The Hyper Text Transfer Protocol, or HTTP, is the most widely used Application layer protocol in the world today. It forms the basis of what most people understand the Internet to be—the World Wide Web. It forms the basis of what most people understand the Internet to be—the World Wide Web. Its purpose is to provide a protocol for the retrieval of Hyper Text Markup Language (HTML) and other documents from Web sites throughout the Internet. Its purpose is to provide a protocol for the retrieval of Hyper Text Markup Language (HTML) and other documents from Web sites throughout the Internet.

Application Layer Protocols HTTP – Hyper Text Transfer Protocol HTTP – Hyper Text Transfer Protocol FTP – File Transfer Protocol FTP – File Transfer Protocol POP – Post Office Protocol POP – Post Office Protocol SMTP – Simple Mail Transfer Protocol SMTP – Simple Mail Transfer Protocol SSL – Secure Socket Layer SSL – Secure Socket Layer Telnet – for remote computer access Telnet – for remote computer access