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Further assume that the sequence number for the very

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Unformatted text preview: ients, each getting 20Mbps. 40% of the client requests are served at 20Mbps and 60% of the requests are delivered at 1Gbps, resulting in an average rate of 608Mbps. Only a reduction by 2Mbps on average despite a 20% reduction in server link bandwidth. This shows how efficient caching can be! Server 80Mbps 50 ms 25 Mbps 200 ms 1 Gbps 0 ms Client Cache 25 Mbps 200 ms 25 Mbps 200 ms 1 Gbps 0 ms Client Cache 25 Mbps 200 ms 1 Gbps 0 ms Client Figure 2 Cache 1 Gbps 0 ms Client Cache ECE374: First Midterm 5 Problem 3: Putting it all together (20 Points, 15 minutes) For this problem you should familiarize yourself with Figure 3 first. Initially, assume that the client wants to retrieve the www.cnn.com home page but has no information about the www.cnn.com web server IP address. www.cnn.com DNS root server Internet DNS .com server local DNS server Client Institutional Cache Figure 3 a. (4 Points) Describe the process of the client obtaining the IP address for the hostname www.cnn.com under the assumption that it is not cached at the local DNS server and that the local DNS server has not cached an entry for the .com DNS server. (Describe this for the recursive case!) Answer: Client contacts local DNS, local DNS contacts root DNS, root DNS contacts TLD DNS, TLD DNS contacts authoritative DNS, IP for www.cnn.com is propagated back on the same rout. b. (4 Points) We know that www.cnn.com is a very p...
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