created in order to connect users and facilitate the performance of tasks. Networks therefore exist for applications. Without applications software, users can do little on a network. Network application software allows users to tap the power of networks in increasingly creative ways.
Currently network applications can be classified into three kinds :
network-ignorant
network-aware
network-intrinsic
Network-ignorant applications are essentially standalone applications that can be hosted on a single file server and be made available to all users on a network. Users can run the application on their desktops and make changes on files available through the application. However, there is no concurrency control, if two users try to use the application simultaneously, data can be lost or corrupted.
Network-aware applications are very similar to network-ignorant applications in that they too offer single copy hosting on a server, and access by multiple users over a network. However, the difference is concurrency control.
Network-aware applications such as Paradox offer the advantages of record- or file-locking, which locks down a record or file in use by any user on a network, thus preventing overwrites by other users. Most client-server applications today are network-aware applications. Their primary value lies in using the network to extend the abilities of a PC and to share network resources.
Network-intrinsic applications include distributed databases, compile servers, compute servers, and multitasking communications servers. Network operating systems today are seeking to provide more multitasking, more memory, faster processors, and programming interfaces in order to make network-intrinsic programs more powerful.
Network applications are selected based on the type of work that needs to be done. A complete set of application-layer programs is available to interface with the Internet. Each application program type is associated with its own application protocol. Some examples include:
1. HTTP is the World-Wide-Web communications protocol used to connect to web servers. Its primary function is to establish a connection with a web server and transmit HTML pages to the client browser.
2. Post Office Protocol 3 (POP3) is an application-layer protocol supported by e-mail programs for the retrieval of electronic mail. POP3 is a standard e-mail server commonly used on the Internet.
3. File Transfer Protocol (FTP) is a simple file utility program for transferring files between remote computers, which also provides for basic user authentication.
4. Telnet is a remote access application and protocol for connecting to remote computer consoles, which also provides for basic user authentication.
5. Simple Network Management Protocol (SNMP) is used by network management programs for monitoring the network device status and activities.
The 7 Layers of the OSI Model
The Open Systems Interconnection model (OSI model) is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers.
The OSI model consists of seven layers:
Application
Presentation
Session
Transport
Network
Data Link
Physical
What do the seven layer OSI?
The TCP/IP model is a description framework for computer network protocols created in the 1970s by DARPA, an agency of the United States Department of Defense. It evolved from ARPANET, which was the world's first wide area network and a predecessor of the Internet. The TCP/IP Model is sometimes called the Internet Model or the DoD Model.
