Round robin, weighted fair queuing, and priority queuing Let us compare three re

Question

Round robin, weighted fair queuing, and priority queuing Let us compare three resource allocation policies. Recall that Round robin simply gives each queue a turn to transmit a packet. Priority queuing allows the queue with the highest priority to be continuously serviced until it is empty. A particular implementation f weighted fair queuing looks at the head of each queue and transmits the packet that would finish transmission quickest under the Generalized Processor Sharing (GPS) scheme. GPS is an ideal fluid flow scheduler, and is defined as: if we have n queues with priority p_1, p_2, ..., pn, then the bandwidth allocated to queue j per time step is p_t/sigma t* pt. Suppose we have queue A and queue B with packets arriving: Queue A has priority 1 and Queue B has priority 3 (higher number indicating higher priority). The outgoing link has bandwidth 1 MBps. Once a packet begins transmitting, it cannot be preempted by other packets. Fill in the following table for round robin scheduling, priority queuing, and weighted fair queuing.

Explanation / Answer

Round robin scheduling -

At t=0, the scheduler will look for packet in queue A, and since the queue is empty, the scheduler will pick the packet from queue B.

At t=1, the scheduler will look for packet in queue B, and pick the packet from queue B.

Priority queuing -

Queue B has the high priority, so the scheduler will pick from queue B till its empty.

Weighted fair queuing -

Queue A has the priority 1 and Queue B has the priority 3.

So, the bandwidth of queue A is 1/(1+3) = 0.25

The bandwidth of queue B is 3/(1+3) = 0.75

If there is no packet in queue, full bandwidth will be allocated to other queue.

Time (s) Queue A arrived packet size (MB) Queue B arrived packet size (MB) Queue A departed packet size (MB) Queue B departed packet size (MB) Remaining packet in Queue A Remaining packet in Queue B t = 0 3 1 0 2 t = 1 1 1 1 1 t = 2 1 1 1 1 t = 3 2 1 1 2 t = 4 1 0 2 t = 5 4 1 0 5

Related Questions

Navigate

• Browse (All)
• Browse R
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.