Computer networks play a dominant role in transmitting information within CPA firms and other companies. A network is simply a set of computers (or terminals) interconnected by transmission paths. These paths usually take the form of telephone lines; however, other media, such as wireless and infrared transmission, radio waves, and satellite are possible. The network serves one purpose: exchange of data between computers and terminals.
Advantages of Networks
Computer networks provide several advantages. Organizations may be geographically dispersed, with offices located all over the world. Computers at each site need to transfer and exchange data, frequently on a daily basis and sometimes even in real-time. A network provides the means to exchange such data.
Even if the organization is not geographically dispersed and only has one office, networks can serve useful functions. Networks permit efficient sharing of resources. For example, if there is too much work at one site, the network allows the work to be transferred to another computer in the network. Such load sharing enhances productivity by allowing a more even and better utilization of an organization's resources.
Backup capability is an especially important feature of networks. For instance, if one computer fails, another computer in the network can take over the load. This might be critical in certain industries such as financial institutions.
Networks can be used to provide a very flexible work environment. An organization can allow its employees to connect to the network and work from home or "telecommute." A network makes it easier for employees to travel to remote locations and still have access to critical data such as sales for last week or research data from a project.
Data flows between computers in a network using one of three methods. Simplex transmission is in one direction only. An example of simplex transmission is radio or television transmission. Simplex transmission is rare in computer networks due to the one-way nature of data transmission. Half-duplex transmission-information can flow in both directions-is found in many systems. However, it is not possible for the information to flow in both directions simultaneously. In other words, once a query is transmitted from one device, it must wait for a response to come back. A full-duplex system can transmit information in both directions simultaneously; it does not have the intervening stop-and-wait aspect of half-duplex systems. For high throughput and fast response time, full-duplex transmission is essential.
Data switching equipment is used to route data through the network to its final destinations. For instance, data switching equipment is used to route data around failed or busy devices or channels.
In designing the network, three factors must be considered. First, the user should get the best response time and throughput. This is especially important for interactive sessions between user applications. Throughput involves transmitting the maximum amount of data per unit of time.
Second, the data should be transmitted along the least-cost path within the network, as long as other factors, such as reliability, are not compromised. The leastcost path is generally the shortest channel between devices and involves the use of the fewest number of intermediate components. Furthermore, low priority data can be transmitted over relatively inexpensive telephone lines, while high priority data can be transmitted over expensive high speed satellite channels.
Third, maximum reliability should be provided to assure proper receipt of all data traffic. Network reliability includes not only the ability to deliver error-free data but also the ability to recover from errors or lost data in the network. The network's diagnostic system should be capable of locating problems with components and perhaps even isolating the component from the network. …