300-420 Exam Dumps : Designing Cisco Enterprise Networks (ENSLD) v1.1

Forward error correction and quality of service are the two listed techniques that directly improve application experience in a Cisco SD-WAN design. Forward error correction protects selected application traffic by sending recovery information so packet loss can be corrected without waiting for retransmission. That is especially useful for real-time voice and video traffic, where retransmission delay can degrade quality. QoS improves application treatment by classifying, marking, queuing, shaping, and prioritizing traffic according to business intent and application sensitivity. Cisco SD-WAN designs commonly combine application-aware routing, QoS, and loss-mitigation features to keep critical traffic on the best path and preserve service quality during congestion or impairment. A stateful firewall, AMP, and Cisco Umbrella improve security posture, but they do not primarily improve application experience in the forwarding-quality sense asked by the question. They may protect applications, but they do not directly address loss, delay, jitter, and congestion treatment. Therefore, FEC and QoS are the best answers. Reference topics: Cisco SD-WAN application experience, FEC, QoS, loss mitigation, real-time traffic handling.

NETCONF: SSH-based; built to support candidate configuration. RESTCONF: HTTPS-based; lacks support for two-phase commit transactions.

NETCONF and RESTCONF both use YANG data models, but they use different transport and transaction behaviors. NETCONF is traditionally SSH-based and was designed as a network configuration protocol with datastore concepts such as running, startup, and candidate configuration where supported. The candidate datastore enables staged configuration changes and a commit workflow, which is useful for transactional network changes. RESTCONF exposes YANG-modeled resources through an HTTP-based REST interface, typically protected with HTTPS. It is simpler for web-style application integration because it uses familiar HTTP methods, URIs, and payload encodings such as XML or JSON. However, RESTCONF does not provide the same full two-phase commit transaction model associated with NETCONF candidate configuration workflows. Therefore, the correct mapping is that NETCONF is SSH-based and built to support candidate configuration, while RESTCONF is HTTPS-based and lacks support for two-phase commit transactions. In Cisco programmability design, NETCONF is often selected for robust configuration transactions, whereas RESTCONF is often selected for simpler API-driven integration.

Traffic shaping is required in the parent policy when hierarchical QoS uses CBWFQ in the child policy for low-bandwidth remote sites. In Cisco hierarchical QoS, the parent policy commonly shapes outbound traffic to the real available rate of the WAN service, especially when the physical interface speed is higher than the provider committed rate. The child policy then applies class-based queuing, such as CBWFQ and LLQ, inside the shaped rate. This structure creates an artificial congestion point on the router so the child queues can schedule packets predictably instead of allowing the provider to drop traffic after it exceeds the service rate. Policing in the child policy would drop excess packets and is not the normal prerequisite for nested CBWFQ. CBWFQ is supported in child policies within hierarchical designs, and parent shaping is the mechanism that makes the hierarchy effective. This is especially important on low-bandwidth WAN links where voice, video, and business-critical applications require deterministic treatment. Reference topics: hierarchical QoS, CBWFQ, parent shaping, child queuing, WAN QoS design.