Question

The nearest Facebook server from UNT DP is in Fort Worth, TX. The copper cable connection between UNT DP and the Facebook server is 60 km long and the propagation speed through the copper cable is 2.5 x 108 m/s. The transmit rate and receive rate is 500 Mbps. Now consider the HTTP protocol and suppose that initial downloaded page from Facebook server is 5,000 bits in size, and that the initial downloaded page contains 6 referenced objects from the Facebook server. Each referenced object is 20,000 bits long. Assume packets containing only control signals (ACK or handshaking) are 200 bits long. Answer the below questions. Assume that N parallel connections each get 1/N of the link bandwidth.

a. What would be the total time required to download the complete page using non-persistent HTTP? (7 Points)

b. What would be the total time required to download the complete page using 2 parallel instances of non-persistent HTTP? (7 Points)

c. What would be the total time required to download the complete page using persistent HTTP? (7 Points)

d. Which is better non-persistent HTTP, parallel instances of non-persistent HTTP, or persistent HTTP? (1 Point)

Answer 1

a)

(200/524,288,000+200/524,288,000+200/524,288,000+5000/524,288,000)+(200/524,288,000+200/524,288,000+200/524,288,000+5000/524,288,000)

= (0.0000011444 + 0.0000095367) + (0.0000011444 + 0.0000095367)

= 0.0000106811 + 0.0000106811

= 0.0000213622(seconds)

b)

Let Tp be the one way propagation delay between client and server for non-persistant parallel instances.

(200/524,288,000+Tp+200/524,288,000+Tp+200/524,288,000+Tp+5000/524,288,000+Tp)+

(200/(524,288,000/2)+Tp+200/(524,288,000/2)+Tp+200/(524,288,000/2)+Tp+5000/(524,288,000/2)+Tp)

= ( 0.0000106811 + 4Tp ) + ( 0.0000152588 + 4Tp )

= 0.0000259399 + 8Tp (seconds)

The propagation speed for copper cable is 2.5*108 m/s Tp=10/(2.5*108)=4*108(The propagation

speed copper cable is more the optic fiber cable.)

c)

(200/524,288,000+200/524,288,000+200/524,288,000+5000/524,288,000)+(200/524,288,000+5000/524,288,000)

= 0.0000106811 + 0.0000038147 + 0.0000095367

= 0.0000106811 + 0.0000133514

=  0.0000240325

d)

The non persistent HTTP is better than persistant because it contains less transmission speed.