Final answer:
Measure network operations to establish a network performance baseline during typical usage to capture normal operational characteristics, avoiding peak or maintenance times, and measure over a sustained period for accuracy.
Step-by-step explanation:
The most appropriate time to measure network operations for establishing a network performance baseline is during a period of typical network usage. This should not be during peak usage times nor during maintenance windows when the network might not be fully operational. Instead, the goal is to capture the normal operational characteristics of the network, which means choosing a representative time period when the users are engaged in routine activities. Measurements should be comprehensive and include key performance indicators such as latency, throughput, error rates, and usage patterns. It is also beneficial to measure over a sustained period, like a week, to account for daily and weekly fluctuations, providing a more accurate baseline for future comparisons.