Consider N Peers （ user ） distribute F=15Gb A file of . The server has us=30Mbps Upload rate of , Download rate per peer di=2Mbps, The upload rate is u. Please target customers separately - Server distribution mode and P2P There are two cases of distribution mode , about N=10,100 and 1000 as well as u=500kbps,1Mbps and 2Mbps Each combination of , Chart minimum distribution time .（ notes ：k=10^3,M=10^6,G=10^9）

answer ： For customers - Server distribution mode （C-S）, Minimum distribution time and upload rate u irrelevant , And N of . The minimum distribution time in each case is shown in the table below , Below , The unit is seconds .

N      C-S                        P2P
500kbps 1Mbps 2Mbps
10 7500 7500 7500 7500
100 50000 18750 11539 7500
1000 500000 28302 14563 7500

It can be seen that , about C-S pattern , Minimum distribution time with N And linear growth .

about P2P pattern , Minimum distribution time with N The growth rate of the two groups has been slowed down , close to log function . And the higher the upload rate of the client , The minimum distribution time is affected by N The smaller the impact , It can transfer files to more users in a short time .

The specific steps are as follows ：

N

NF/us

F/min(di)

F/us

NF/(us+∑ui)

Minimum distribution time /s

10

C-S

5000

7500

7500

P2P

500kbps

7500

500

4286

7500

1Mbps

7500

500

3750

7500

2Mbps

7500

500

3000

7500

100

C-S

50000

7500

50000

P2P

500kbps

7500

500

18750

18750

1Mbps

7500

500

11539

11539

2Mbps

7500

500

6522

7500

1000

C-S

500000

7500

500000

P2P

500kbps

7500

500

28302

28302

1Mbps

7500

500

14563

14563

2Mbps

7500

500

7389

7500

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