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Digital Communication

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Digital Communication:
ØDigital Communication is the one which uses digital signals for transmitting information between source and destination. Digital signal consists of discrete values rather than continuous values. ØPower requirement in case of digital communication is less a compared to Analog communication. Since the bandwidthrequirement in digital systems is more thus, they consume less power.  ØDigital communication equipment’s are costly and digital signal require more bandwidth for transmission. ØDigital signal is represented by square wave. ØDigital signals are used in computers.

Analog Communication

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Analog Communication:ØThe term analog refers to any physical device or signal that can continuously vary in strength or quantity. for example, voltage in a circuit. ØThe term analog communication refers to any method of communication based on analogue principles. ØTypically, this term is associated with voice transmission because voice transmission facilities such as telephone were initially. ØAnalog communication is used in phones (Both landline and cellular), modems, fax machines, cable television. ØIn analog communication, the data is transferred from transmitter to receiver with the help of analog signal. Analog signal possesses continuous varying amplitude with time. Any type of data such as voice, sound etc. can be transferred through an analog signal.

ØFirstly, the data needs to be converted into electrical form. As voice, sound is non-electric in nature, it can be converted into electric form with the help of transducer. Then this signal is passed through the communication channel. …

Parallel Communication

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Parallel communication: ØIn telecommunication and data transmission, parallel communication is the process of sending multiplebits simultaneously over a communication channel or computer bus. ØIn Parallel Transmission multiple bits are sent together.
ØParallel Transmission is faster than serial transmission to transmit the bits. ØParallel transmission is used for short distance i.e. computer to printer. ØIn Parallel Transmission, eight bits are transferred at one clock pulse. It is a fast way to transmit as it uses many input/output lines for transferring the data. ØParallel Transmission is half-duplex since the data is either sent or received.

Communication Service Methods

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Communication Service Methods:ØThere are several methods in which data can be transmitted between sender and receivers ·Serial communication ·Parallel communication A)Serial communication: ØIn telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. ØIn serial communication, data is in the form of binary pulses. In other words, we can say Binary One represents logic HIGH or 5 Volts, and zero represents a logic LOW or 0 Volts. ØSerial communication can take many forms depending on the type of transmission mode and data transfer. ØGenerally, Serial Transmission is used for long distance I.e. computer to computer ØSerial Transmission is full-duplex as the sender can send as well as receive the data. ØSerial Transmission is simple and reliable

Peer-to-peer Model

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Peer-to-peer ModelØThe peer to peer systems contains nodes that are equal participants in data sharing. ØAll the tasks are equally divided between all the nodes. ØThe nodes interact with each other as required as share resources. This is done with the help of a network.
ØSince nodes in peer to peer networks act as both clients and servers, it is difficult to provide adequate security for the nodes. This can lead to denial of service attacks. ØMost modern operating systems such as Windows and Mac OS contain software to implement peer to peer networks. ØAdvantages of Peer to Peer Computing ·Each computer in the peer to peer network manages itself. So, the network is quite easy to set up and maintain.

Client/Server Model

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Client/Server ModelØIn client server systems, the client requests a resource and the server provides that resource. ØA server may serve multiple clients at the same time while a client is in contact with only one server. Both the client and server usually communicate via a computer network and so they are a part of distributed systems.

ØThe client server computing works with a system of request and response. The client sends a request to the server and the server responds with the desired information. ØThe client and server should follow a common communication protocol so they can easily interact with each other. All the communication protocols are available at the application layer. ØA server can only accommodate a limited number of client requests at a time. So it uses a system based to priority to respondto the requests. ØAn example of a client server computing system is a web server. It returns the web pages to the clients that requested them. ØAdvantages of Client Server Computing ·

Distributed Systems

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Distributed Systems ØIn this type of processing different CPU are connected to the network and are controlled by single CPU. ØFor example, in air reservation system there exists different terminals and processing is done from many locations and all the computers are controlled by the single main processor. ØThis type of network is called distributed network. ØA distributed system contains multiple nodes that are physically separate but linked together using the network. All the nodes in this system communicate with each other. ØEach of these nodes contains a small part of the distributed operating system software. ØA diagram to better explain the distributed system is:

ØTypes of Distributed Systems