Data Communications Introduction
Defined data communications Introduced data communications needs Communications model Overview of networks Introduce Internet
Data, Data Communication
Data is an entity that convey some meaning based on some mutually agreed upon rules/conventions between a sender and a receiver. Data Communication deals with the transmission of signals in a reliable and efficient manner
Topics covered include:
Signal Transmission Transmission Media Signal Encoding Interfacing Data link control Multiplexing
Computer Science and Data Communications Merger
In 1970s and 1980s The computer communications ...view middle of the document...
Intelligent PSTN Network Voice mail, remote data access, pagers, fax, e-mail, cordless phones, cell phones and cellular networks and internet portals
A Communication Model
The fundamental purpose of communications system is the exchange of data between two parties. The key elements of this model are:
Source: The device generates the data to be transmitted
Examples: Telephones and personal computers.
Transmitter: The transmitter transforms and encodes the information in such a way as to produce some transmittable form that can be transmitted across some sort of transmission system.
E.g. a Modem takes a digital bit stream from personal computer and transform that bit stream into an analog signal that is transmitted to the telephone network.
Transmission System: It carries data from source to destination. This can be single transmission line or a complex network connecting source and destination. Receiver: It accepts the signal from the transmission system and converts it into a form that can be handled by the destination device.
E.g. A modem accepts and analog signal coming form a network or transmission line and converts it into a digital bit stream.
Destination: Takes the incoming data from the receiver.
A Communications Model
The key tasks that must be performed in a data communications system are:
Transmission system utilization: need to make efficient use of transmission facilities typically shared among a number of communicating devices.
Multiplexing is used to allocate the total capacity of the transmission medium among a number of users. Congestion control is used to manage the demand of transmission services
To communicate, a device must interface with the transmission system. once an interface is established, signal generation is required for communication
There must be synchronization between transmitter and receiver, to determine when a signal begins to arrive and when it ends Exchange Management: If data are to be exchanged in both directions over a period of time, the two parties must cooperate.
E.g. Telephone conversation, (Simplex/duplex), data communication. Following two items are under exchange management.
Error detection and correction are required in circumstances where errors cannot be tolerated Flow control is required to assure that the source does not overwhelm the destination by sending data faster than they can be processed and absorbed
Addressing and Routing, A source system can indicate the identity of the intended destination, and can choose a specific route through this network Recovery allows an interrupted transaction to resume activity at the point of interruption or to condition prior to the beginning of the exchange e.g. Database transactions and file transfer Message formatting has to do with an agreement between two parties as to the form of the data to be exchanged or transmitted Frequently need to provide some measure of security in a data communications...