Data Communications Basics

Data communications is as old as the oldest electronic computer. Its nature, however, has changed drastically over the many years of its existence. Because data communications has many facets, it means different things to different people. This article attempts to present the varying aspects of data communications and explore some of the issues to varying degrees. In a fundamental sense, data communications entails the transmission of information from one point to another. This definition is indeed very broad. Traditionally, however, one thinks of data communication as being the exchange of digital information, as opposed to analog information. Here it is assumed that the underlying information is digital and the communicating entities are computers capable of transmitting, receiving, and processing the information. The notion of one point to another is equally vague. Whether in the spatial or the temporal dimension, the transmission of information has certain performance requirements. They are generally very dependent on the nature of the information that underlies the bits to be communicated. The accuracy requirements for data transmission tend to be much higher. Indeed, there exist techniques that provide accuracy that is so high that one often talks of “error-free” communications, even though there still exists a positive probability of bits being received in error. This is further explored in this article, where one can obtain a fuller appreciation of precisely why the term error-free is used and occasionally misused. Besides accuracy, other metrics of performance exist as well. Even though other metrics of performance (such as reliability, operation under faults, recovery time, etc.) are important, the data communications field has evolved with accuracy, delay, and throughput being the prime metrics of performance. The set of rules, procedures, and specifications for accomplishing a particular task of the communications process is generally referred to as a protocol. Protocols cover the entire spectrum of data communications and must be designed well so that under normal conditions they themselves do not become the bottleneck of the communications process. On the other hand, they must be robust enough so that when something goes wrong the protocol is sophisticated enough to either repair it or issue some type of a warning that can be used by a human operator/user to rectify the problem. One of the most widely used set of protocols has been developed under the umbrella of the OSI model. The current technology used for data communications has evolved over several years. It has been applied to a number of different environments, including wide area networks, local area networks, metropolitan area networks, etc. There are at least two trends in the communications environment that are bound to have significant impacts on the data communications field as well. There is one fundamental observation that must be made. The field of data communications is not only within reach and fascinating, but is also challenging and multidimensional. Several technical and nontechnical disciplines must work together in order to improve what we collectively understand as being the field of data communications. Keywords: OSI model; metric; accuracy; protocols; physical layer; network layer; transport layer; session layer; presentation layer; application layer; cellular communication