Network applications may be defined as software applications used in networks that require or substantially benefit from the presence of networked computers. Networks essentially are 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.
Networked applications came into being with the advent of the client-server model in the 1980s and 1990s, when LANS (Local-Area Networks) and WANs (Wide-Area Networks) proliferated, and corporations increasingly began to rely on centralized computer programs for all business functions. This meant that robust data-handling applications were placed on central network servers, rather than on desktop workstations. Networked users then used thin-client interfaces at their desktops to connect with network applications and perform business tasks such as accounting, querying for data, data analysis, and reporting. This model was found to be cost- and resource-effective. Soon, cost and infrastructure efficiencies dictated the use of sophisticated back-end network applications for all corporate needs including networked e-mail, scheduling, data storage, and data back-ups. This reliance increased as the use of networks expanded and the Internet gained visibility and significance. Locally networked computing began to make the switch to Internet computing, with users now relying for applications on large central servers accessible over the Internet. Currently the drive toward hosted applications has led Internet service providers and web site hosting servers to offer bundled services that include messaging, web e-mail and instant messaging, scheduling, content management, directory services, newsgroups, listservs, authentication, and other services as part of the Internet access and application package.
Telnet, Email, MajorDomo, and FTP are examples of early network applications that have continued to maintain their significance; and other complex and newer applications continue to crowd the market. Telnet is a UNIX program using TCP/IP (Transmission Control Protocol/Internet Protocol) that allows computers to connect remotely to other hosts or from a client to a server on the network as if connected directly. The most common usage of Telnet today is to allow users to log into remote computers on which they have an account and perform various functions such as editing and processing of email. Email or electronic mail programs such as Microsoft Outlook, Netscape Mail, Eudora, or Lotus Notes allow users to send electronic text, image, or multimedia messages to single or group computer-users on a local network or over the Internet. MajorDomo is a list server management program that allows users to automatically set up and manage e-mail discussion lists called listservs.
FTP or File Transfer Protocol is a TCP/IP program that allows users on computers to connect to remote servers or hosts and download or upload files, explore and organize directories, and manage files on the remote host system from a distance. Interestingly FTP was the standard means for transfer of files on the Internet before the advent of the HyperText Transfer Protocol (HTTP) and the World Wide Web. Although many FTP functions have been taken over by HTTP, FTP is still used extensively for file transfer on the Internet, especially by webmasters making updates to Web sites.
Currently network applications can be classified into three kinds— network-ignorant, network-aware, and network-intrinsic. Network applications can also include programs written for network administration and management such as NetWare's SYSCON, as well as printer and disk management utilities. Increasingly utilities are included in network operating systems.
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, which means that if more than one user works on the same file over the network, changes made will always override the existing copy of the file, and will not discretely reflect the input of all users. Also, 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. The specific database record or word-processing file in use is locked down for every other user and becomes available only when the first user relinquishes control by closing the record or file. These programs have been created or modified expressly to allow usage by multiple concurrent users. Database applications, word-processing programs, communications software, and electronic mail are all network-aware applications. 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.
However, network-aware applications do not fully harness the power of networks since they use the network only as a peripheral sharing device. Although the file server hosts the program and data, it does not do any processing. All processing is done by individual users' computers, including all concurrency control. This is being replaced today by network-intrinsic applications, which share or distribute processing power among network computers, and is also known as distributed computing. Application programs of this kind have multiple components. One piece is the server, which does data processing, and the other is the client, which communicates with the user. A database server with front and back ends is a good example. The front end records user requests and displays formatted data to the user. Users can make queries, write reports, and create new databases. The back end manages data, concurrency control, and security. Basically, when a user submits a query for data, all search and sorting through the database is done by the server rather than the user's computer. The back-end returns the specific record requested rather than the entire file, as in the case of network-aware applications, which expect the user's computer to then do the processing. With a database server, the question of multiple user traffic is addressed by concurrency control at the server back-end. The two programs, front- and back-end, work together to create one application. 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.
Cross-platform connectivity has become an increasingly important issue as dissimilar hardware and software platforms are distributed across networks. In the past organizations sought to standardize on one platform or another, an approach no longer followed, as platform innovation continues. Interoperability across diverse platforms is a vital goal for any architecture that claims to be suitable for network applications. On the Internet, TCP/IP offers a means to ensure cross-platform connectivity across Windows, Macintosh, and UNIX platforms.
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