Ixchariot - Instant performance assessment of complex networks from pre- to post-deployment.
Uptime Kuma - A fancy self-hosted monitoring tool.
iperf - A TCP, UDP, and SCTP network bandwidth measurement tool
Statsignal - Statsignal is a simple and cost-effective way to monitor your website or server and publish a status page of your system.
Ostinato - Ostinato is a packet crafter and traffic generator for network engineers. Wireshark in Reverse.
UptimeRobot - Free Website Uptime Monitoring