Cisco SD-WAN TCP Optimization Functions
What two functions describe the TCP optimization tool used in the Cisco SD-WAN? (Choose two.)
Community Votes
80% of anonymous learners picked answer BC. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
The question tests knowledge of TCP optimization components: SACK for efficient retransmission and local termination to bypass WAN congestion.
This question examines the specific mechanisms of Cisco SD-WAN TCP optimization, focusing on its use of Selective Acknowledgment (SACK) and local connection termination at the WAN edge. The correct options highlight how these features improve throughput by managing window sizes and reducing latency.
Many candidates choose option D (remote termination), incorrectly assuming a dual-ended proxy is required or that termination happens at both ends, whereas the feature primarily terminates locally to optimize the path.
Community Discussion (7 comments)
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Expert Analysis
Why the Answer Is Correct
Cisco SD-WAN TCP optimization works by terminating the TCP connection locally at the WAN edge router (Option C). This creates a proxy-like effect where the SD-WAN device handles the retransmissions over the WAN link instead of the end hosts. Additionally, it utilizes TCP Selective Acknowledgment (SACK) (Option B) to inform the sender about which segments have arrived successfully, allowing for more efficient retransmission of only lost packets rather than entire windows.Why the Other Options Are Wrong
Option A is too generic; standard TCP uses ACKs, but SACK is the specific optimization feature. Option D is incorrect because while dual-ended proxies are possible, the core function described in the context of 'local' optimization usually refers to the single-ended or primary termination point at the edge closest to the client or as configured, and specifically, the documentation highlights local termination as the key mechanism for the optimization engine itself. Option E is incorrect because TCP optimization is primarily for data traffic throughput, not specifically for control traffic packet loss handling.Community Comment Notes
Community consensus strongly supports BC, with users noting that the feature terminates connections locally and uses SACK to maximize throughput. One user referenced official Cisco documentation confirming that TCP optimization fine-tunes TCP parameters and uses SACK. Another comment mentioned that while dual-ended proxies exist, the fundamental description aligns with local termination and SACK usage.Official Reference
Exam Strategy
When studying SD-WAN features, focus on the specific protocols and mechanisms used for optimization, such as SACK and NPTv6. Understand whether a feature operates at the control plane or data plane, and whether it modifies traffic flow directly.
Frequently Asked Questions
Why does TCP optimization terminate connections locally?
Local termination allows the SD-WAN device to handle retransmissions over the WAN link, preventing end-host timeouts due to high latency or packet loss.
What is the role of SACK in this optimization?
SACK allows the receiver to acknowledge non-contiguous blocks of received data, enabling faster and more efficient retransmission of only lost packets.
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