Editor's Note: This article was updated June 5, 2009.

• What is network monitoring?
• How important is network monitoring?
• What can network monitoring systems monitor?
• What kind of networks can they monitor?
• What strategic tasks can network monitoring systems do?
• What questions can network monitoring answer?
• What can network monitoring do for me?
• What tools will I find in network monitoring systems?
• What kinds of network monitoring systems are available?
• What do they cost?

Network monitoring for a corporate network is a critical IT function that can save money in network performance, employee productivity and infrastructure cost overruns. A network monitoring system monitors an internal network for problems. It can find and help resolve snail-paced webpage downloads, lost-in-space e-mail, questionable user activity and file delivery caused by overloaded, crashed servers, dicey network connections or other devices.

Network monitoring systems (NMSs) are much different from intrusion detection systems (IDSs) or intrusion prevention systems (IPSs). These other systems detect break-ins and prevent scurrilous activity from unauthorized users. An NMS lets you know how well the network is running during the course of ordinary operations; its focus isn't on security per se.

Network monitoring can be achieved using various software or a combination of plug-and-play hardware and software appliance solutions. Virtually any kind of network can be monitored. It doesn't matter whether it's wireless or wired, a corporate LAN, VPN or service provider WAN. You can monitor devices on different operating systems with a multitude of functions, ranging from BlackBerrys and cell phones, to servers, routers and switches. These systems can help you identify specific activities and performance metrics, producing results that enable a business to address various and sundry needs, including meeting compliance requirements, stomping out internal security threats and providing more operational visibility.

Deciding specifically what to monitor on your network is as important as giving network monitoring a general thumbs up. You must be sure that your corporate network topology map is up to date. That map should accurately lay out the different types of networks to be monitored, which servers are running which applications on which operating system, how many desktops need to be counted into the mix and what kind of remote devices have access for each network. A dose of clarity at the outset makes choosing which monitoring tools to purchase down the line somewhat simpler.