DCNUNIT-V

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Transport Layer Protocol


            Cryptography, Network Security - Download

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CSMA,MAC

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Carrier Sense Multiple Access To minimize the chance of collision and, therefore, increase the performance, the CSMA method was developed. The chance of collision can be reduced if a station senses the medium before trying to use it. Carrier sense multiple access (CSMA) requires that each station first listen to the medium before sending. CSMA is based on the principle “sense before transmit” or “listen before talk.” CSMA can reduce the possibility of collision, but it cannot eliminate it. The reason for a space and time model of a CSMA network. Stations are connected to a shared channel (usually a dedicated medium). At time t1, station B senses the medium and finds it idle, so it sends a frame. At time t2 (t2 > t1), station C senses the medium and finds it idle because, at this time, the first bits from station B have not reached station C. Station C also sends a frame. The two signals collide and both frames are destroyed. Vulnerable Time The vulnerable t...
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Line Coding

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Line Coding Line coding is the process of converting digital data to digital signals. We assume that data, in the form of text, numbers, graphical images, audio, or video, are stored in computer memory as sequences of bits. Line coding converts a sequence of bits to a digital signal. At the sender, digital data are encoded into a digital signal; at the receiver, the digital data are recreated by decoding the digital signal. Below figure shows the process.     Common Characteristics Signal Element versus Data Element Let us distinguish between a data element and a signal element. In data communications, our goal is to send data elements. A data element is the smallest entity that can represent a piece of information: this is the bit. In digital data communications, a signal element carries data elements. A signal element is the shortest unit (timewise) of a digital signal. We define a ratio r which is the number of data elements ...
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Virtual LAN(VLAN)

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Virtual LAN(VLAN) The Formal definition of a virtual local area network (VLAN) as a local area network configured by software, not by physical wiring or connectivity. Above Figure shows the same switched LAN divided into VLANs. The whole idea of VLAN technology is to divide a LAN into logical, instead of physical, segments. A LAN can be divided into several logical LANs, called VLANs. Each VLAN is a work group in the organization. VLANs create broadcast domains. Here two switches are connected. This is a good configuration for a company with two separate buildings. Each building can have its own switched LAN connected by a backbone. People in the first building and people in the second building can be in the same work group even though they are connected to different physical LANs.
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