EE 450 EXAM FOR 15-441 COMPUTER NETWORKS FALL 2020-ALL ANSWERS CORRECT-GRADED A

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15-441: Computer Networks Fall 2020 Midterm Name: Andrew ID: INSTRUCTIONS: There are 16 pages (numbered at the bottom). Make sure you have all of them. Please write your name on this cover and a... t the top of each page in this booklet. If you find a question ambiguous, be sure to write down any assumptions you make. It is better to partially answer a question than to not attempt it at all. Be clear and concise. Limit your answers to the space provided. Q1 Q2 Q3 Q4 Q5 Q6 / ? / ? / ? / ? / ? / ? Q7 Q8 Q9 Q10 Q11 Total / ? / ? / ? / ? / ? / ?? 1Stacks and Stuff 1. (8 points) Please answer each or the following short questions. Briefly explain your answer. (a) Why is changing the IP layer of the Internet protocol stack hard? Solution: It is the narrow waist of the Internet. Changing it requires that all the routers forwarding Internet traffic and all end-hosts implement the change. It is very difficult to get so many independent entities to agree and implement the change. (b) What challenge do NATs introduce to the Internet with respect to overcoming failures? Solution: They violate fate sharing by introducing important state into a non-end point of the Internet. (c) Most wireless access points and devices have the option of encrypting traffic. Which OSI layer is that encryption taking place? Solution: Data link (d) Which principle of Internet design does the encryption in part (c) (appear to) violate? Solution: The end-to-end arg [Show More]

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