Linux.com - https://www.linux.com/news/how-monitor-network-protocol-traffic-your-data-center-linux-servers
With Linux in your data centers, you value the ability to monitor different network protocols on your servers. With this gathered information, you can troubleshoot issues or tweak your servers such that they outperform the original specs. Most Linux administrators might recall ntop. It was the de facto standard, text-based tool for monitoring network protocols. That tool has been deprecated, in favor of ntopng (aka The Network Time Protocol Reference Implementation, refactored, the Next Generation).