Consider the time it takes to download a distribution of an

Consider the time it takes to download a distribution of an update to an operating system. The total size of the update is 550 MBytes. The upload bandwidth to the ISP is 10 Mbps. How long will it take to copy this file to 100 hosts using the BitTorrent protocol (calculate the best possible scenario)? Assume that the download bandwidth for each of the hosts is 3 Mbps and upload bandwidth of 500 Kbps.

DIFS Slot Time DIFS STATION A PACKET A ACK SIFS STATION B DIFS DIFS busy medium ACK 4 3 2 1 0 8 7 6 5 Slot Time 5: frozen backoff time Slot Time

Solution

Best possible scenario would be parallel system where all host download the update in parallel.

Total size of the update = 550 MBytes = 550*8 Mbits

Upload bandwidth to the ISP = 10Mbps

So 10Mbits take 1 second to upload

So 550*8 Mbits will take = 550*8/10 = 440 seconds

Download bandwidth for each of the hosts = 3Mbps

So 3Mbits download in 1 second

So 550*8 Mbits will be downloaded in = 550*8/3 = 1466.67seconds

So total time it takes to copy file to 100 hosts using the BitTorrent protocol (best possible scenario)

= 440+1466.67 = 1906.67 seconds