Network Monitoring Solutions

The term network monitoring describes the use of a system that constantly monitors a computer network for slow or failing
systems and that notifies the network administrator in case of outages via email, pager or other alarms. It is a subset of
the functions involved in network management.
While an intrusion detection system monitors a network for threats from the outside, a network monitoring system monitors the
network for problems due to overloaded and/or crashed servers, network connections or other devices.
For example, to determine the status of a webserver, monitoring software may periodically send an HTTP request to fetch a
page; for email servers, a test message might be sent through SMTP and retrieved by IMAP or POP3.
Commonly measured metrics are response time and availability (or uptime), although both consistency and reliability metrics
are starting to gain popularity. The widespread addition of wan optimization devices is having an adverse effect on most
network monitoring tools -- especially when it comes to measuring accurate end to end response time because they limit round
trip visibility.
Status request failures, such as when a connection cannot be established, it times-out, or the document or message cannot be
retrieved, usually produce an action from the monitoring system. These actions vary: an alarm may be sent out to the resident
(SMS, email,...) sysadmin, automatic failover systems may be activated to remove the troubled server from duty until it can
be repaired, etcetera.
Monitoring the performance of a network uplink is also known as network traffic measurement, and more software is listed
there.
Website monitoring services usually have a number of servers around the globe - in America, Europe, Asia, Australia and other
locations. By having multiple servers in different geographic locations, a monitoring service can determine if a Web server
is available across different Networks worldwide. The more locations used, the better the picture on your website
availability.