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                      Routing algorithm Routing  is process of establishing the routes that data packets must follow to reach the destination. In this process, a routing table table is created which contains information regarding routes which data packets follow. Various routing algorithm are used for the purpose of deciding which route an incoming data packet needs to be transmitted on to reach destination efficiently. Classification of Routing Algorithms: The routing algorithms can be classified as follows: 1. Adaptive Algorithms – These are the algorithms which change their routing decisions whenever network topology or traffic load changes. The changes in routing decisions are reflected in the topology as well as traffic of the network. Also known as dynamic routing, these make use of dynamic information such as current topology, load, delay, etc. to select routes. Optimization parameters are distance, number of hops and estimated transit time. Further these are cla

Network Devices (Hub, Repeater, Bridge, Switch, Router, Gateways and Brouter) 1. Repeater  – A repeater operates at the physical layer. Its job is to regenerate the signal over the same network before the signal becomes too weak or corrupted so as to extend the length to which the signal can be transmitted over the same network. An important point to be noted about repeaters is that they do not amplify the signal. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength. It is a 2 port device. 2. Hub  –  A hub is basically a multiport repeater. A hub connects multiple wires coming from different branches, for example, the connector in star topology which connects different stations. Hubs cannot filter data, so data packets are sent to all connected devices.  In other words,  collision domain  of all hosts connected through Hub remains one.  Also, they do not have intelligence to find out best path for data packets which leads t

         DTE- DCE interferences Definition of DTE:- DTE (Data terminating equipment) is a terminal residing at physical layer or can be anything that could be able to generate to consume digital data like computers. In other words, it is an assembly that operates either as a source of or as a destination for  binary digital data. There is no direct mechanism for DTE to communicate, so communication occurs place through some intermediary devices. Let’s take a real life example which will illustrate the working of DTE. Suppose your brain is a DTE device which can generate and consume ideas. If your brain wants to communicate with your friend’s brain to interpret the idea generated by your brain, It would not be practically possible. Consequently, your brain will take help of your vocal chords for the interpretation of the idea. That’s how a DTE works. Customer devices that connect to the telephone company’s (telco’s) equipment are known as  CTE(Customer telephony Equipment

              Switching techniques Switched communication networks  are those in which data transformed from source to destination is routed between various intermediate nodes. In large network , there can be multiple paths from sender to receiver. The switching techniques will decide the best route for data transmission. There are mainly three typical Switching Techniques available for digital traffic: Circuit Switching Message Switching Packet Switching 1) Circuit Switching Circuit Switching is a technique that directly connects the sender and the receiver in an unbroken path. For example take telephone switching equipment establishes a path that connects the caller’s and reciever’s telephone by making a physical connection. Routing decisions in circuit must be made when the circuit is first established, but there are no decisions made after that time. A complete end to end path must exist before communication can take place. Once the connection h

  Public switched telephone network PSTN  is the worldwide collection of interconnected public telephone network that was designed primarily for analog telephone calls. PSTN is also referred to as the landlines / plain old telephone service -- POTS. This is the system that has been is general use since the late 1800's. Properties of PSTN It is also known as Plain Old Telephone Service (POTS) It has evolved from the invention of telephone by Alexander Graham Bell. The individual networks can be owned by national government, regional government or private telephone operators. Its main objective is to transmit human voice in a recognizable form. It is an aggregation of circuit-switched networks of the world. Originally, it was an entirely analog network laid with copper cables and switches. Presently, most part of PSTN networks is digitized and comprises of a wide variety communicating devices. The present PSTNs comprises of copper telephone line

            Shanon capacity  Data rate governs the speed of data transmission. A very important consideration in data communication is how fast we can send data, in bits per second, over a channel. Data rate depends upon 3 factors: The bandwidth available Number of levels in digital signal The quality of the channel – level of noise Two theoretical formulas were developed to calculate the data rate:  one by Nyquist for a noiseless channel, another by Shannon for a noisy channel. Noisy Channel : Shannon Capacity – In reality, we cannot have a noiseless channel; the channel is always noisy.  Shannon capacity is used, to determine the theoretical highest data rate for a noisy channel. Shannon capacity is used, to determine the theoretical highest data rate for a noisy channel: Capacity = bandwidth * log 2 (1 + SNR) In the above equation,  Bandwidth is the bandwidth of the channel SNR is the signal- to- noice ratio Capacity is the capacity of the

Data Communication | Transmission Impairment In communication system, analog signals travel through transmission media, which tends to deteriorate the quality of analog signal. This imperfection causes signal impairment. This means that received signal is not same as the signal that was send. Causes of impairment – Attenuation –  It means loss of energy. The strength of signal decreases with increasing distance which causes loss of energy in overcoming resistance of medium. This is also known as attenuated signal. Amplifiers are used to amplify the attenuated signal which gives the original signal back. Attenuation is measured in  decibels(dB) . It measures the relative strengths of two signals or one signal at two different point. Attenuation(dB) = 10log10(P2/P1) P1 is power at sending end and P2 is power at receiving end.                       Distortion It means change in the shape of signal. This is generally seen in composite signals with different