HTML clipboardIntroduction and Basics of Data Communication Model
Data Communications is the transfer of data or information between a source and
a receiver. The source transmits the data and the receiver receives it. Data
communication involved the following like communication networks, different
communication services required, the kind of networks available, protocol
architectures, OSI models, TCP/IP protocol models etc. Data Communication is
interested in the transfer of data, the method of transfer and the preservation
of the data during the transfer process.
In Local Area Networks, we are interested in "connectivity", connecting
computers together to share resources. Even though the computers can have
different disk operating systems, languages, cabling and locations, they still
can communicate to one another and share resources.
The purpose of Data Communications is to provide the rules and regulations that
allow computers with different disk operating systems, languages, cabling and
locations to share resources. The rules and regulations are called protocols and
standards in Data Communications.
Source
It is the generator of data that will pass on the destination using networks.
Without any request source never passes the data to destination. So, if source
is passing the data means any of the destinations is requesting for data using
some query languages.
Transmitter
It is simply a device used to convert the data as per the destination
requirement. For example a modem, converts the analog (telephonic signals)
signal to digital (computer signals) signals and alternatively digital to analog
also.
Transmission System
To transmit the data on different connected systems we use different
transmission systems. Data transmission using transmission system means the
physical transfer of data over point-to-point or point-to-multipoint
communication channels. Example of such channels are copper wires, optical
fibers even wireless communication channels etc.
Receiver
This receives the signals from the transmission system and converts it into a
form that is suitable to the destination device. For example, a modem accepts
analog signal from a transmission channel and transforms it into digital bit
stream which is acceptable by computer system.
Destination
It is simply a device for which source device sends the data.
Data Communication System Tasks
There are some tasks performed by the communication systems are
Signal Generation
To transmit the data over the transmission system, communicating device must be
able to generate and receive these signals. The generation of the signals should
be in such a way that the resultant signal can be acceptable by the transmission
mediums.
Interface
Device must interface with the transmission system to communicate or transfer
the data over network.
Data Synchronization
It is the process of establishing consistency among data from a source to
destination devices and vice versa and continuous harmonization of the data over
time.
Exchange Management
For meaningful data transaction there should be some management of data being
exchanged. Both the transmitter and receiver should adhere to some common
convention about the format of data, amount of data, time required, data format
etc.
Transmission System Utilization
Due to the importance of Data transmissions without interruptions or failures
the transmission systems is usually well dimensioned and are being operated with
margins that minimize the possibility of outages. Various techniques are
available to allocate the total capacity of a transmission channel among
connected devices like Digital, Analog, Multiplex, Simplex, Duplex, Half-Duplex
etc.
Error Detection and Correction
In any communication system transmitted data is prone to error. Either it is
because of transmitted signal getting distorted in the transmission medium
leading to misinterpretation of signal or errors introduced by the intermediate
devices. Error detection and correction is required in cases where there is no
scope for error in the data transaction. We can think of file transfer between
two computers or even on remote network computers where there is a need for
this. But in some cases it may not be very important as in the case of
telephonic conversation.
Flow Control
At the time of transmission of data, source computer is generating data faster
than receiver device capable to receive it. To handle such problem, there is
some kind of flow control mechanism used. Before getting started the
transmission of data they have to agree upon between two communication devices.
Addressing
When more than two devices share a transmission facility, a source system must
somehow indicate the identity or address of the destination. Addresses are in
form of IP or we can say ftp address and there are used lots of credentials.
Routing
Routing means to send data to appropriate destinations. In this process the
evolved computer ensures that the data is being sent on destination system only
or any other hacking happening. To eliminate such problem developers uses SSL
level security.
Communication Network and Services
Communication Network is set of equipment or say facilities that provide a
communication services like to transfer of data between two or more nodes
located in any of its geographical point. Example of such networks includes
computer networks (LAN/WAN), intranet networks, telephone networks, television
broadcasting networks, cellular networks etc.
Radio and Television Networks
These networks are very common network usage various stations to transmit an
ensemble of signals simultaneously over network of cables. Aside from selecting
the station of interest, the role of the user in these services is passive.
Relatively high audio and video quality is expected here but a significant
amount of delay (fraction of second) can be tolerated even in live broadcasting.
Telephone Networks
This service is real-time service provided by a network. Two persons are able to
communicate by transmitting their voice across the network. These services is
called connection-oriented service because to establish such communication users
must first interact with the network.
Cellular Networks
These networks extends the normal telephone service to mobile users who are free
to move within a regional area covered by an interconnected array of smaller
geographical areas called cells. Each cell has a radio transmission system that
allows it to communicate with users in its area. Cellular provides also support
a roaming service where a subscriber is able to place calls while visiting
regional area other than the home.
There are many other network services like Video on Demand, Streaming
Audiovisual, and Audio-Video Conferencing etc available.