Question

Consider the pattern of red and green packet arrivals to a router's output port queue, shown below. Suppose each packet takes one time slot to be transmitted, and can only begin transmission at the beginning of a time slot after its arrival. Indicate the sequence of departing packet numbers (at t =1,2,3,4,5,7,8) under round robin scheduling, where red starts a round if there are both red and green packets ready to transmit after an empty slot. Give your answer as 7 ordered digits (each corresponding to the packet number of a departing packet), with a single space between each digit, and no spaces before the first or after the last digit, e.g., in a form like 7654321 ). PNate: You can Fird mare examples of problems similat ta this tate.]

Answer 1

The sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under round-robin scheduling is 1 2 3 4 5 7 8.

Step-by-step explanation:

The sequence of departing packet numbers (at t = 1, 2, 3, 4, 5, 7, 8) under round-robin scheduling can be determined by analyzing the pattern of red and green packet arrivals. Here is the sequence:

1. At t = 1, the red packet departs.
2. At t = 2, the green packet departs.
3. At t = 3, the red packet departs.
4. At t = 4, the green packet departs.
5. At t = 5, the red packet departs.
6. At t = 7, the red packet departs.
7. At t = 8, the green packet departs.

Therefore, the sequence of departing packet numbers is 1 2 3 4 5 7 8.

Answer 2

In the given round-robin scheduling scenario, the departing packet sequence at time slots 1, 2, 3, 4, 5, 7, and 8 is 7421538. This sequence ensures fairness in transmitting both red and green packets in a cyclic order.

Step-by-step explanation:

In round-robin scheduling, each packet is given a turn to be transmitted in a cyclic order. The packets arrive in the order: R1, G2, R3, G4, R5, G7, R8. At each time slot, the scheduler selects the next packet in line, and if the opposite color is also ready, it starts a new round. Let's break down the sequence:

1. t=1: R1 starts the transmission.

2. t=2: G2 is the next packet.

3. t=3: R3 gets its turn.

4. t=4: G4 is transmitted.

5. t=5: R5 follows.

6. t=6: No packet arrives.

7. t=7: G7 starts a new round.

8. t=8: R8 completes the sequence.

The round-robin scheduling alternates between red and green packets until all packets are transmitted. In this case, the sequence 7421538 represents the departing packet numbers at time slots 1, 2, 3, 4, 5, 7, and 8.

In summary, the round-robin scheduling ensures fairness by providing equal opportunities for both red and green packets. The sequence is determined by the order of packet arrivals and the rule of starting a new round when both red and green packets are ready.