- Consider The Scenario In The Figure Below In Which A Server In Lan B Is Connected To A Router By A 1 Gbps Link With A 1 1 (270.02 KiB) Viewed 46 times
Consider the scenario in the figure below in which a server in LAN B is connected to a router by a 1 Gbps link, with a 1 ms propagation delay. That router in turn is connected to a second router over a 1.54 Mbps link with a 200 ms propagation delay. This second router is an access router for LAN A, on which there is a single local web server and N hosts, all connected by 1 Gbps links with negligible propagation delay. All N hosts want to download a file of size F, only one copy of which exists on the origin server on LAN B. file, size F origin server Local Area Network B 11 Gbps LAN public Internet 1.54 Mbps access link Local Area Network A. 1 Gbps LAN local web cache a) If the web-cache server is turned off, what is the total length of time (in terms of N and F) taken to download the file by all N hosts. You can neglect the HTTP request message in your calculation as well as all TCP segments used to establish the connection. b) Repeat this calculation for the case of the web cache being turned on. c) Once again repeat the calculation to find the total length of time (in terms of N and F) taken to download the file by all N hosts, where this time the web cache is turned off, and the N hosts on LAN A and the origin server on LAN B use a peer-to-peer architecture to distribute the file. You can assume that each of the N hosts can use 50% of their 1Gbps links for download and 50% for upload. You can neglect any messages sent to initiate the P2P distribution. d) Taking N = 100, and F = 1 Gigabytes, calculate the total download time for each of the three scenarios above and identify which of the three scenarios takes the shortest time.