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# hw5 - duplex transmission which supports multiple...

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Zhou, HuanXian HW5 ID: 0225418 EE136 Instructors: Kang Xi 1. A disadvantage of the CSMA/CD is the capacity wasted due to contention. Suppose that time is divided into discrete slots, with each of N stations attempting to transmit with probability p during each slot. What fractions of slots are wasted due to multiple simultaneous transmission attempts? The fraction of slots wasted due to multiple transmission attempts is equal to the probability of 2 or more transmission attempts in a slot Pr[2 or more attempts] = 1 – Pr[no attempts] – Pr[1 attempt] = 1 – (1 – p) N – Np(1 – p) N–1 2. In today's typical Ethernet, the stations are connected to an Ethernet switch using twisted pairs. In this case, do we still need CSMA/CD to control the medium access? Explain why. No, because the Ethernet switch uses the switching technology, it is a fully
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Unformatted text preview: duplex transmission, which supports multiple simultaneous transmissions; therefore, there is no need of CSMA/CD. 3. Station A, B and C are interconnected through an Ethernet switch. At a certain moment, A and B start sending packets to C simultaneously. Do you think this will cause a transmission collision at station C? Do we need CSMA/CD to handle this? If not, what is the solution? It would not cause a transmission collision at station C, because a switch supports multiple transmissions. Therefore we don’t need CSMA/CD to handle it. The following is the solution for this transmission: Switches have internal memory to buffer incoming packets, When two or more packets contend for the same destination output, only one packet is delivered at a time, other packets are delayed in the memory....
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• Spring '10
• KANG XI
• Ethernet Switch, transmission attempts, simultaneous transmission attempts, multiple transmission attempts

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