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Basic principles of data transmission may also be covered within the computer science/computer engineering topic of data communications, which also includes computer networking or computer communication applications and networking protocols, for example routing, switching and inter-process communication. This course is all about networking concepts. In this course how data communication takes place is explained and The OSI model,TCP/IP protocol, its various layers functions concepts are included.
LECTURE #3 Communication Tasks There are some key tasks that must be performed in a data communication system Elements can be added, deleted, or merged together Transmission System utilization Interfacing Signal Generation Synchronization Exchange Management Error Detection and Correction Flow Control Addressing Routing Recovery Security Network Management Transmission System Utilization Need to make efficient use of Transmission facilities that are shared among a no. Of communicating devices For Example: Techniques like Multiplexing to allow multiple users to share total capacity of a Transmission Medium Congestion Control: TX. System should not be overwhelmed by traffic Interfacing A device must have an Interface with the Transmission System/Transmission Medium Signal Generation Electromagnetic Signals travel over Transmission Medium. Once an interface is established, Signal generation is required Properties of Signals Capable of being propagated over TX.
Medium Interpretable as data at the Receiver Synchronization The transmission and the reception should be properly synchronized. Synchronization means that the receiver must be able to determine, when to docsity.com. Expect a new transmission and when to send acknowledgements. In other words transmitter and receiver should have an agreement on the nature as well as timing of the signals Exchange Management If the data needs to be exchanged in both directions over a period of time, both parties must cooperate as follows Whether both devices must transmit simultaneously or take turns Amount of Data to be sent at one time Format f the Data What to do when an Error Arises Error Detection and Correction In all comm. Systems, there is a potential risk for errors and impairments. Signals are distorted to some extent before reaching their destination. Error Detection & Correction needs to be employed in Data Processing Systems where a change in say the contents of a file cannot be tolerated Flow Control To make sure that source does not overwhelm destination by sending data faster than it can be handled and processed Addressing & Routing If TX facility is shared by two or more devices, source must specify the identity or the address of the destination system and if Tx.
System is itself a system, a proper route must be allocated that the data will take in order to reach the desired destination Recovery If a data transmission is interrupted due to a fault somewhere in the system, recovery techniques are needed. The objective is either to resume activity at the point of interruption and to restore the state of the system to what it was prior to the interruption Security Security is very important issue in a Data Communication System. The sender needs to be assured that Only the Intended receiver receives the data Data is delivered unaltered Introduction to Protocol In computer Networks, communication occurs between two entities in different systems.
O Entity is anything sending and receiving information o SYSTEM is a physical object containing more than one entities docsity.com. Now, two entities in different systems cannot just send data and expect to be understood. For communication to occur, these entities must agree on a PROTOCOL PROTOCOLS As discussed earlier, “Protocol is a set of rules governing communication” o Two computers cannot just send bit streams to each other and expect to be understood o Entities must agree on a PROTOCOL Same Example French and German Protocol defines: What is Communicated? How it is Communicated?
When it is Communicated? KEY elements of a PROTOCOL Syntax: Represents the Structure or the format of the Data Meaning the order in which data is presented For Example First eight bits to be Sender address Next eight to be Receiver’s Address The Rest to be Data Semantics: Refer to the Meaning of each section of bits How is a particular pattern to be interpreted? What action should be taken based on interpretation?
For Example Does an address identify the route to be taken or the final destination of the message? Timing Refers to 2 characteristics: When data should be sent? How fast it should be sent? For Example If sender produces data at 100 Mbps But Receiver can only process data at 1 Mbps The TX. Will overload receiver and data will be lost docsity.com. Protocol Architecture Instead of having a single Module for performing communication, there is a structured set of modules that implement communications function” This structure is called Protocol Architecture Let’s explain it by an example of File transfer system.