200-901 Network Fundamentals Practice Question
A network engineer is analyzing a packet capture and notices that a TCP session between a client and server is experiencing performance issues. The capture shows that the client sends a segment with the Push (PSH) flag set, but the server's acknowledgment does not immediately follow; instead, the server waits and sends a single acknowledgment for multiple segments. Which TCP mechanism is the server using to optimize network efficiency?
⚠ Common exam trap
Watch out — candidates often confuse delayed acknowledgment with congestion control algorithms like slow start, which also affect TCP performance but in a different way.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
TCP delayed acknowledgment
The server is using delayed acknowledgment, a TCP feature where the receiver delays sending an ACK to potentially combine acknowledgments for multiple segments, reducing overhead. This is distinct from congestion control or window management mechanisms. The behavior described—waiting and then sending a single ACK for multiple segments—is characteristic of delayed ACK, which is commonly enabled by default in many TCP stacks.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
TCP delayed acknowledgment
Why this is correct
Delayed acknowledgment is a TCP optimization where the receiver waits for a short period or until it has received multiple segments before sending an ACK. This reduces the number of ACK packets and improves network efficiency. The scenario describes the server waiting and then sending a single acknowledgment for multiple segments, which is exactly how delayed ACK works. It is commonly used to reduce overhead, especially for interactive traffic.
- ✗
TCP slow start
Why it's wrong here
TCP slow start is a congestion control algorithm that gradually increases the congestion window size after a connection is established or after a timeout. It does not describe the behavior of delaying acknowledgments. Slow start affects the sender's transmission rate, not the receiver's acknowledgment timing. The scenario describes the receiver intentionally delaying ACKs, which is a different optimization mechanism.
- ✗
TCP selective acknowledgment (SACK)
Why it's wrong here
Selective acknowledgment allows the receiver to acknowledge non-contiguous blocks of data, which helps the sender retransmit only missing segments. It is used to improve performance in the presence of packet loss. The scenario describes the receiver waiting to send a single ACK for multiple segments, which is not related to SACK. SACK would be seen as additional ACK blocks, not delayed ACKs.
- ✗
TCP window scaling
Why it's wrong here
TCP window scaling is an option that allows the receive window to be larger than 65,535 bytes by using a scaling factor. It is used to improve throughput on high-bandwidth, high-latency networks. It does not involve delaying acknowledgments; rather, it increases the amount of data that can be in flight. The scenario does not mention large windows or high latency, so window scaling is not the mechanism at play.
Go deeper
Related to this question
About these practice questions
One of 975 original 200-901 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 200-901 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-901 exam.