ISO OSI.Layers1

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The Application layer of the OSI model is where users communicate to the computer. The Application layer is responsible for identifying and establishing the availability of the intended communication partner and determining if sufficient resources for the intended communication exist.

Although computer applications sometimes require only desktopresources, applications may unite communicating components from morethan one network application; for example, file transfers, e-mail, remoteaccess, network management activities, client/server processes, and infor-mation location. Many network applications provide services for communication over enterprise networks, but for present and future internetworking, the need is fast developing to reach beyond their limits. Today, transactions and information exchanges between organizations are broadening to require internetworking applications like the following:

World Wide Web (WWW) Connects countless servers (the numberseems to grow with each passing day) presenting diverse formats. Mostare multimedia and include some or all of the following: graphics, text,video, and even sound. Netscape Navigator, Internet Explorer, and otherbrowsers like Mosaic simplify both accessing and viewing Web sites.

E-mail gateways Are versatile and can use Simple Mail Transfer Proto-col (SMTP) or the X.400 standard to deliver messages between differente-mail applications.

Electronic Data Interchange (EDI) Is a composite of specialized stan-dards and processes that facilitates the flow of tasks such as accounting,shipping/receiving, and order and inventory tracking between businesses.

Special interest bulletin boards Include the many Internet chat roomswhere people can connect and communicate with each other either byposting messages or by typing a live conversation. They can also sharepublic domain software.

Internet navigation utilities Include applications like Gopher and WAIS, as well as search engines like Yahoo!, Excite, and Alta Vista, which help users locate the resources and information they need on the Internet.

Financial transaction services Target the financial community. Theygather and sell information pertaining to investments, market trading,commodities, currency exchange rates, and credit data to their subscribers.