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Boston University CS 625 _Assignment2_GRADED

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There are three parts to this assignment. Please make sure to complete all parts. Part 1: Data Rate Calculations In the last module, you learned a formula for calculating the bit rate, R = b/t, that is, the number of bits divided by the time. This formula expresses the number of bits that are transmitted over a circuit in a given period of time. In practice, however, we are not only concerned with the number bits transmitted, but also with the number of data bits transmitted over a circuit. The data bits are those that the sender decides to send to the receiver, and do not include the overhead bits used by the networking protocols involved. Recall that the protocols that send messages on a circuit use some of the available bits to store metadata (overhead) for protocol communication. From a data perspective, the bit rate on a circuit can be termed the maximum data rate because it calculates the theoretical maximum number of data bits that can be sent over a network circuit if the protocols were to use no overhead bits. Effective data rate is a rate that takes into account the overhead of the protocols involved. In this part, you will perform effective data rate calculations with two scenarios. Each scenario gives you the maximum data rate of the circuit, along with details of the protocol(s) involved and asks you to calculate the transmission efficiency and effective data rate. For full credit, the calculations you use to derive the answers must be shown. Scenario 1: 19,500 ASCII characters are transmitted over a 3 Mbps circuit. The protocol uses 8-bits to encode each ASCII character, and adds an additional parity bit to help detect errors. a. Calculate the transmission efficiency of this protocol. Application bits = 8 bits, Overhead bits = 1 bit (1 parity), ASCII Characters = 19,500 Size of 19,500 character = 19,500*8 = 156,000 Total bits to be transferred = 19,500*9 = 175,500 Transmission Efficiency = number of application bits / number of total bits transmitted = 156,000/175,500 = 88.89% b. Determine the effective data rate of sending these characters over the circuit using the abovedefined protocol. Effective Data Rate = Transmission Efficiency * Maximum Data Rate = 0.89 * 3Mbps = 2.67Mbps Scenario 2: A person types a plaintext email consisting of 350 characters into their email client, and the characters are encoded with 16-bit Unicode. When the person hits the Send button, the email client uses the SMTP protocol to transmit the message, with an SMTP header of 100 bytes. SMTP is running over TCP over IP over Ethernet, and the Ethernet link is running at 1Gbps.

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