331: STUDY DATA COMMUNICATIONS AND NETWORKS

 1. Discuss computer networks (5 hrs)  2. Discuss data communications (15 hrs)

 PERFORMANCE STANDARD ◦ Given a network system, identify and illustrate the different data communications components clearly  Objectives: ◦ Define elements of a communication system ◦ Define data communications ◦ Discuss various types of transmission media and their characteristics ◦ Discuss encoding of information for transmission ◦ Discuss types of signal & their characteristics ◦ Relate data capacity of a channel and bandwidth ◦ Classify media based on bandwidth ◦ Discuss channel organization

Discuss channel organization

 Data may be transmitted between two points in two different ways.  Lets consider sending 8 bits of digital data (1 byte).  These bits may be sent all at once (in parallel), or one after the other (serial).

 Each bit uses a separate wire.  If there is eight bits sent at a time, this will require 8 wires, one for each data bit.

 To transfer data on a parallel link, a separate line is used as a clock signal.  This serves to inform the receiver when data is available.  In addition, another line may be used by the receiver to inform the sender that the data has been used, and its ready for the next data.

 Require more wire and more costly.  Faster than serial transmission because the data can be transmitted in less time.

 Each bit is sent over a single wire, one after the after.  No signal lines are used to convey clock (timing information) and handshake signals.  There are two methods that are synchronous and asynchronous.  A common standard for serial communications is RS232  Serial data is slower than parallel, but suited to long distances.

 In synchronous transmission, the bit stream is combined into longer "frames," which may contain multiple bytes.  Each byte, however, is introduced onto the transmission link without a gap between it and the next one.  It is left to the receiver to separate the bit stream into bytes for decoding purposes.  In other words, data are transmitted as an unbroken string of 1 s and 0s, and the receiver separates that string into the bytes, or characters.

 The information is received and translated by agreed upon patterns.  As long as those patterns are followed, the receiving device can retrieve the information without regard to the rhythm in which it is sent.  Patterns are based on grouping the bit stream into bytes. Each group, usually 8 bits, is sent along the link as a unit.  The sending system handles each group independently, relaying it to the link whenever ready, without regard to a timer.

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