A peertopeer system consists of a server containing a copy o

A peer-to-peer system consists of a server (containing a copy of a file), and 20 peers. The file size is 10,000 bits, the upload rate of the server is 5,000 bits/sec., and the upload rate of each peer is 2, 500 bits/sec. The download rate of each peer is 4,000 bits/sec. What is the minimum time required to distribute the file to all the peers under the peer-to-peer model ?

Solution

Time 0: File is in server. Let us transfer the file to two clients at once each at 2500bits/sec.

Time 4: File is on server and two clients. Let us start transferring it from server to two clients again, but now we have two clients from previous step who have the file, so from these clients let us start transferring to another two new clients.

Time 8: Now file is on 4 new clients. Total there 6 clients with the file and the server. Let us start transferring it from server to two clients again, but now we have 6 clients who have the file, so from these clients let us start transferring to another 6 new clients.

Time 12: Now file is on 8 new clients. Total there 14 clients with the file and the server. Let us start transferring it from server to two clients again, but now we have 14 clients who have the file, but there are 4 other clients who don\'t have the file. so from the old clients let us start transferring to another 4 new clients.

Time 16: All clients have the file.