CCNA (200-301) Exam Practice Questions

DiffServ QoS model

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Q5. Which of the following is true about DiffServ QoS model?

A. Does not prioritize traffic, but provides best effort delivery.

B. Prearranges a path for priority traffic on end-to-end basis.

C. Handles traffic dynamically, QoS is applied on a per-hop basis.

D. All the above.

Correct Answer: C

Explanation:

Quality of Service: There are 3 basic types of QoS:
1.Best effort delivery
2.Integrated Services Model
3.Differentiated Services Model
1.Best Effort Delivery: The best effort delivery method does not distinguish between a priority traffic and a non-priority traffic. The packets are forwarded in the order that they arrive. However, the routers or switches put their best effort to forward the packets that are received.
2.Integrated Services (IntServ) Model: The protocol that does scheduling and reserving adequate path bandwidth (end-to-end bandwidth) for application is known as Resource Reservation Protocol (RSVP). The source application requests QoS parameters through RSVP from the network devices along the route to destination. The minimum set of commonly agreed parameters is arrived at, and the source is informed of the same. RSVP enables traffic prioritization according to a pre-determined set of rules.
3.Differentiated Services Model (DiffServ): In the DiffServ model, the resources are dynamically arranged. The advantage over IntServ model is that the bandwidth utilization is more efficient in DiffServ. With IntServ, QoS is applied on a per-flow basis, whereas it is applied on a per-hop basis on DiffServ.

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