Monitor one 

A comprehensive, all-in-one and graphical all-in-one network monitoring software for network uptime and health monitoring. Provides sophisticated features for real-time monitoring and graphing using SNMP, trending, logging and long term analysis.
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MultiPing 

MultiPing is an application built for monitoring graphically one or more TCP/IP hosts, while providing detailed historical information about the collection period to monitor uptime and performance or to just keep track of general connectivity.
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Network Equipment Performance Monitor 

NEPM goes beyond polling-based monitoring to true downtime and event detection, tracking, and correction. Unique links reveal downtime or intrusion causes, while performance graphs highlight networked element throughput and error rate.
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