300-420 · Question #388
A customer requested that a guaranteed service line be enabled for a manufacturing business in different countries. On the customer side, the QoS-aware application is used to process large data chunks
The correct answer is D. Configure a domain-based QoS strategy with PHB behavior.. The key constraint is 'minimum required resources on ISP network nodes.' DiffServ (Differentiated Services) is a domain-based, class-based QoS model: packets are marked with a DSCP value at the network edge, and each ISP core node makes a forwarding decision based solely on that
Question
A customer requested that a guaranteed service line be enabled for a manufacturing business in different countries. On the customer side, the QoS-aware application is used to process large data chunks. The application cannot tolerate drops and latency should be as low as possible. Which QoS model must an engineer employ to use the minimum required resources on the ISP network nodes?
Options
- AEnable a flow-based QoS strategy with queuing elements.
- BImplement an end-to-end QoS strategy with SLA.
- CImplement a group-based QoS strategy with FECs enabled.
- DConfigure a domain-based QoS strategy with PHB behavior.
How the community answered
(23 responses)- A4% (1)
- B4% (1)
- C9% (2)
- D83% (19)
Explanation
The key constraint is 'minimum required resources on ISP network nodes.' DiffServ (Differentiated Services) is a domain-based, class-based QoS model: packets are marked with a DSCP value at the network edge, and each ISP core node makes a forwarding decision based solely on that marking using a Per-Hop Behavior (PHB) - such as Expedited Forwarding (EF) for low-latency, guaranteed bandwidth. Because core nodes are stateless (no per-flow reservations), DiffServ requires minimal memory and processing resources while still guaranteeing low latency and no drops for the marked class. IntServ/RSVP (flow-based, option A) requires per-flow state on every node - expensive and unscalable across ISPs. Option B describes an SLA commitment but not a specific QoS model. Option C (group-based with FECs) is not a standard QoS architecture for this use case.
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