what tool is best used to verify a network's transmission speed?

A reliable tool to verify a network's transmission speed is iPerf. It measures the maximum TCP and UDP bandwidth performance between two hosts and provides detailed metrics on throughput, latency, and jitter. Other options include Speedtest.net for a user-friendly interface and practical testing of internet speed from various locations. Additionally, tools like Wireshark can help analyze network traffic but are more complex and focused on packet analysis.