Parts 28, 29, and 30

Consider the figure below, for which there is an institutional network connected to the Internet. Suppose that the average (upload or download) object size is 1 Mbytes. Also suppose that the amount of time it takes from when the router on the Internet stde of the access link forwards an HTTP request until it receives the response is 3 seconds on average. Answer questions (28)-(30) Origin server Origin servers Public Internet Public intenet 15 Mbps access link 15 Mbps access link 100 Mbps LAN 100 Mbps LAN- Institutional cache Institutional network institutional network Figure 2: Bottleneck between an institutional network and the Internet (28) Suppose an object is uploaded/downloaded in one attempt. How much time elapses from the click to the successful file delivery without cache (figure on the left)? LAN delay Access delay: Time (before) to the Internet: Time of ONE successful delivery: (29) Suppose the successful probability to access a link is 0.2. What is the total average time for a successful file delivery? Avg. attempts to ONE successful link access: Avg. time (before) to the Internet Avg. time to ONE successful file delivery: success probability of network access is also increased to 0.5. What is the average response time? Response time with a cache hit: Th Avg. attempts per successful access: N Response time with a cache miss: Tmiss (30) Now suppose a cache is installed in the institutional LAN and the cache miss rate is 0.4. The Avg. response time