21. Consider the scenario introduced in the previous problem. Now suppose that the link is shared by Bob with four other users. Bob uses parallel instances of non-persistent HTTP, and the other four users use non-persistent HTTP without parallel downloads. (a) Do Bob's parallel connections help him get Web pages more quickly? Why or why not? (b) If all five users open five parallel instances of non-persistent HTTP, then would Bob's paralle' connections still be beneficial? Why or why not? 22. How does SMTP mark the end of a message body? How about HTTP? Can HTTP use the same method as SMTP to mark the end of a message body? Explain 23. Consider distributing a file of F=20 Gbits to N peers. The server has tan upload rate of us=30Mbps, and each peer has a download rate of di=2Mbps and an upload rate of u. For N=10,100, and 1,000 and u=300Kbps,700Kbps, and 2Mbps, prepare a chart giving the minimum distribution time for each of the combinations of N and u for both clientserver distribution and P2P distribution