# Q1: Assume the propagation delay in a broadcast network is 5 A????1s and the frame transmission time 1 answer below »

Q1:

Assume the propagation delay in a broadcast network is 5 A????1s and the frame transmission time is 10 A????1s.

How long does it take for the first bit to reach the destination?

How long does it take for the last bit to reach the destination after the first bit has arrived?

How long is the network involved with this frame (vulnerable to collision)?

Q2:

Explain why collision is an issue in random access protocols but not in controlled access protocols.

Q3:

In a bus CSMA/CD network with a data rate of 10 Mbps, a collision occurs 20 A????1s after the first bit of the frame leaves the sending station. What should the length of the frame be so that the sender can detect the collision?

Q4:

To understand why we need to have a minimum frame size Tfr = 2 A????1 Tp in a CDMA/CD network, assume we have a bus network with only two stations, A and B, in which Tfr = 40 A????1s and Tp = 25 A????1s. Station A starts sending a frame at time t = 0.0 A????1s and station B starts sending a frame at t = 23.0 A????1s.

Do frames collide?

If the answer to part a is yes, does station A detect collision?

If the answer to part a is yes, does station B detect collision?

Q5:

In a BSS with no AP (ad hoc network), we have five stations: A, B, C, D, and E. Station A needs to send a message to station B. Answer the following questions for the situation where the network is using the DCF protocol:

What are the values of the To DS and From DS bits in the frames exchanged?

Which station sends the RTS frame and what is (are) the value(s) of the address field(s) in this frame?

Which station sends the CTS frame and what is (are) the value(s) of the address field(s) in this frame?

Which station sends the data frame and what is (are) the value(s) of the address field(s) in this frame?

Which station sends the ACK frame and what is (are) the value(s) of the address field(s) in this frame?

Q 6:

Suppose you are to design a LAN for a company that has 150 employees, each given a desktop computer attached to the LAN. What should be the data rate of the LAN if the typical use of the LAN is shown below?

Each employee needs to retrieve a file of average size of 10 megabytes in a second. An employee may do this on average 10 times during the eight-hour working time.

Each employee needs to access the Internet at 250 Kbps. This can happen for 10 employees simultaneously.

Each employee may receive 10 e-mails per hour with an average size of 100 kilobytes. Half of the employees may receive e-mails simultaneously.

Q7

Why is there no need for CSMA/CD on a full-duplex Ethernet LAN?

Q8:

How can you configure 8 Android devices to construct a Piconet Bluetooth Network?