Communications Network Question 10 users need to download a

Communications Network Question

10 users need to download a file of size 700M bytes from a server with an upload rate of 100 Mbps. 8 of these users have end systems in enterprise networks, each one with a download and upload rate equal to 30Mbps, while two users are connected to an ISP through DSL home access. One of these two users pays more and has a download rate equal to 50Mbps, while the other user has the basic service with a download rate of 5Mbps. Both the DSL users have an upload rate of 1Mbps. With a file distribution application based on the client-server architecture: Compute the minimum time that is needed for one enterprise network user to download the entire file from the server. Compute the minimum time that is needed for the server to distribute the entire file to all the enterprise users and the home user that pays more. With a file distribution application based on the P2P architecture: Compute the minimum time needed by the server to distribute the file to all the 10 users.

Solution

In client server architecture, the minimum time to download the entire file by an enterprise user = 700 / 30 = 23.33 Sec

The minimum time needed is restricted by the slowest speed connection even if the server\'s upload bandwidth is equally shared by the users.

Hence, total time = 700 / 5 = 140 sec.

In P2P network, users can also download the file from each other. Hence,

since the enterprise users have download and upload rate at 30 Mbps,

In optimal case, 3 enterpise users can download simultaneously from the server and provide the data to 3 other users. They can again provide the data to the 2 enterprise users and they in turn can send it to the ISP users.

The 30 Mbps user can get the file from server in 700 / 30 = 23.33

However, the ISP user with 5 Mbps download speed will always need 700 / 5 = 140 sec. to download the file completely.

Hence, in P2P network as well, the time to distribute the file to all the users will be 140s