2013_Midterm_1_Exam_Solution

Initially assume that the client wants to retrieve

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Unformatted text preview: data to a single client if we assume no other clients are making requests? Answer: Server can send at the max of the bottleneck link: 50Mbps. c. (4 Points) Again we assume only one active client but in this case the caches are on and behave like HTTP caches. A client’s HTTP GET is always first directed to its local cache. 65% of the requests can be satisfied by the local cache. What is the average rate at which the client can receive data in this case? Answer: We assume that requests are serially satisfied. 35% of the requests can be delivered at 50Mbps and 65% at 1Gbps. So the average rate is 667.5Mbps. d. (4 Points) Now clients in both LANs are active and the both caches are on (similar to c). 65% of the requests can be satisfied by the local caches. What is the average rate at which each client can receive data? Answer: 50Mbps link remains bottleneck link, which is not shared between LANs. Answer is same as in c. Note that we assume that the 100Mbps link is shared at fine granularity, so that each client gets up to 50Mbps over that link. e. (8 Points) Now consider Figure 2 where the network has been extended by two additional LANs, and all LANs are connected via 25Mbps links and the throughput of the server link is only 80Mbps. In all four LANs 60% of the requests can be satisfied by the local caches. What is the average rate at which each client can receive data? Answer: Now the server link is the bottleneck link an equally shared by all cl...
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