Data Communications

  As of today our topic is about  Data Communications..so,its a very important subject..each and every software should know about this data communaications...so, let us begin .....
 so our first  we have to know about data, and communication...
 So what is Data?????
 Data is an information stored in digital form..
  So,information is of  two types....

Analog:-  It is a Contineous  form of information..Ex:- ECG, Audio,speech..
Digital:- Binary coded numbers, Alpha numeric  0's  1's  etc.,

Data:-
  
1)raw, unorganisation facts that need to be processed..


Info:-

1)Well organised useful meaning understandable to human..

Communication:-
   Transferring of information from one point to  another point through a communication medium..

                     or 
  
   Establishing a link beween  two points for information exchange..

Data Communication:-

   Transfering of digital information fromone point to the  another point through a communication media..

 Data Communication System:-

     The  information assembled togeather to the a communication medium.

   to develop these there are 5 elements...they are..

   Message:-  An information that can be  communicated.

   EX:- text,speech,audio,

   Sender:- It is a device or human..it may be mobile work station.

  Receiver:- It is also a device which receives.

  Transmission Medium:- It is a physical path through which message travels from sender to  receiver.

  

Protocol:- It defines the rules for sending a data between sender and receiver..

Network:-A set of devices that are interconnected by media to share the information..

                  We  can also  call devices as  nodes,points,stations.

Computer Network:-

     Linking of set of computers that are  interconnected by a medium..

Ex:- Atm to banks, one system connected to  another..

Network Architecture:-

      It defines  the way in which a  Data communication network is arranged.or structured..

 these are classified into 2 types..

   1)point-point 

   2)Broadcast

  In point -to-point  there can be only one point.

  In broadcast no.of subscribers different...

   there are 2 types in broadcasting ..

 1)Broadcasting:-one info is shared by  all systems.

 2)Multicasting:- only one  system some set of subscribers..

Protocol Data Unit..(PDU):-    

    We share information as blocks  of  data or packet..

Ex:- 1000 bytes  we have taken..that is divided into blocks....like 300 b   400 b  300b

 Protocol Stack:-

     List of  protocols is called protocol stack..

  

 Protocols:-

     There are two types of protocols..

1)Connection Oriented.

2)Connection less Protocols.

 1)connection oriented protocols  establishes a logical connections between 2 points prior to the transmission of data..

   In this one system sends  info to recever...and receiver gives info to sender...this is called handshaking..

 

  2)Connection less protocols which uses source & destination addresses without  handshake..

     sender sends request to receiver...but receiver doesnot respond..

      here ther is less reliability..

     This includes syntax and sematics..

     

Syntax mean  some structure..

Sematics:- it describes meaning of each section ..of format...