Question 1:

Consider an 4 x 4 Banyan network. The incoming traffic is i.i.d. (independent and identically distributed). Each input of a switching element has an input buffer which may in maximum hold one packet. If a collision occurs, a winner will be randomly chosen.

Throughput is referring to the per output port throughput. Develop a mathematical model to derive the throughput for this switching network.

Question 2:

One Forward Error Correction (FEC) scheme is to send/piggyback a lower-resolution audio stream as the redundant information together with the original audio stream, as shown in the following diagram.

Please extend this model to cope with up to two consecutive packet losses. You are suggested to use a similar diagram as the one above to illustrate your approach.

Question 3:

Consider the procedure for determining the playout delay for a VoIP connection. Suppose that u=0.2 and K=4. Let the following packets generated: packet 1 generated at time 0, packet 2 at time 20ms, packet 3 at time 40ms, packet 4 at time 60ms, and packet 5 at time 200ms, packet 6 at time 220ms, and packet 7 at time 240ms.

And the receiving time for packet i is ri. And r1= 210ms, r2=270ms, r3=250ms, r4=380ms, r5=450ms, r6=510ms, r7=470ms. Packet 1 is the first packet generated by this VoIP connection.

Please specify the payout time for packet 6 and packet 7, respectively. Justify your answer.

Question 4:

Consider an RTP session consisting of five users, all of which are sending and receiving RTP packets into the same multicast address. Each user sends video at 200kbps.

a) What rate RTCP will limit its traffic to?

b) How much RTCP bandwidth a particular sender will be allocated?

c) How much RTCP bandwidth a particular receiver will be allocated?