Short Tutorial on Communication Networks

A wide range of communication network services are needed to support eservices. This step helps you to identify A communication network is a collection of equipment and physical media, viewed as one autonomous whole, that interconnects two or more stations. At the lowest level, a communication network consists of three components (see Figure 1):

• Stations (data sources/sinks). These entities generate and receive the data handled by the communication network. Examples of the data are voice, computer bits, and TV patterns. A station is effectively an end-point (source/sink) in a communication network. Examples of stations are terminals (text and/or graphics), telephones, sensors (temperature, security), TVs, facsimiles, diskless workstations, personal computers, workstations, minicomputers, or mainframes.  

• Data/signal converters. These devices convert the data to signals for transmission on one end and back to data at the other. Data is propagated from one point to another by means of  signals which are electromagnetic representation of data. An example of a converter is a modem which converts data bits to continuous signals which are transmitted across a network. Converters basically translate  different formats of data and signals (modems are digital to analog converters and codec's are analog to digital converters).  In some networks, called baseband networks, the conversions are bypassed by "pressing" the data directly against the communication wire. In these cases, data and signals are the same.   

• Transmitting facilities. These facilities deliver (transport) the signals across a network. This transport involves finding a path for the signals, sending the signals over the path, and dealing with signal attenuation and distortion over long transmission paths.

Figure 1: Conceptual View of Networks

A communication network may use analog (continuous) or digital (discrete) data for its inputs and outputs. In digital communication systems, all data is digital (it either comes from digital data sources or is converted to digital format). These systems are increasingly being used in most of the current and future distributed applications.

The transmission facilities consist of a wide range of hardware components and software modules. Design of transmission facilities raises questions such as what communication medium to use, how to interconnect the various components (network topology), what methods to use for communication between various components, and what techniques to use for data compression and encryption.  .

Network facilities are generally classified into three categories based on the geographical area covered

• Local area networks (LANs) which do not use common carrier facilities over short distances with speeds up to 100 Mbps. LANs are commonly used to interconnect computers within the same building and organization.

• Wide area networks (WANs) which use common carrier facilities over long distances commonly with speeds in the range of 1.5 Mbps. WANs are used to interconnect remotely located sites and equipment.

• Metropolitan area networks (MANs) are essentially large LANs which cover an entire metropolitan area (a city, a suburb, etc.). The evolving metropolitan area networks can be used to interconnect LANs within a metropolitan area.  

Figure 2 displays a sample corporate communication network. Click here for a short tutorial on networks and the Internet. 

Figure 2: A Sample Corporate Network