Zabbix - Track, record, alert and visualize performance and availability of IT resources

SevOne - SevOne provides network managers with monitoring, troubleshooting, and performance reporting capabilities.

Abusix - Abusix is a network security company that offers email threat protection and network abuse handling solutions to ISPs, Telcos, and Cloud/Hosting Providers to stop the rapidly growing problem of email-borne threats and other kinds of network abuse.

Flowmon - Clever Network Monitoring and Security Solution based on NetFlow, IPFIX and Network Behavior Analysis

FastNetMon - FastNetMon is a very fast DDoS analyzer with sflow/netflow/mirror support.

Obkio - Simple Network Monitoring and Network Troubleshooting software to empower users to identify and troubleshoot network & application slowdown from the end-user perspective.