There are squillions of tools out there, both paid-for and freeware, that enable you to monitor the traffic that's flying down your network. Network Probe, from Norwegian company ObjectPlanet, is what we'd call a traffic level monitor. Rather than storing the detailed contents of every packet it sees, it builds a repository of statistical information about the nature of those packets. It can then give a visual representation of the loading of the network and the types of data travelling across it. Installation of the product is a simple case of running the installer and letting it do its stuff. As with most tools of this type there's some low-level packet driver software required to allow the network card to absorb all packets, not just those addressed to it. But on our Windows XP machine the process was automatic and needed no interference from us. When it's running, the product sits in a Web browser window and gives an overview of the traffic on the network. This is useful, because it means you could sit a monitoring agent on each segment of the network and connect to each from your desktop PC's browser. There's a textual representation in the top half of the window and a graphical image in the bottom. The eight tabs at the top of the main page allow you to list traffic in a number of different ways – by protocol, by host, by network card, by host-to-host conversation, and so on. You can jump between the various lists, either by clicking the tab or by right-clicking an item in the list (either in the text pane or the graph pane) and picking something from the resulting pop-up. So if, for instance, you're looking at the "conversations" overview tab, which shows all the pairs of machines between which there have been transmissions, you can right-click on a line and ask to see all the protocols used by that conversation, the protocols used by one or other of the hosts, or the other conversations in which either of the hosts has been involved. Where screens contain graphs that you'd like to drill into, you're often presented with popup data when you hover over things – particularly the pie charts that show packet size distributions in the Network tab. Someone's clearly thought about how you would want to navigate around the various information items, as it's very well done. Configuration options
The configuration options for the product are basic, but that's all you need. You can tell it how much data to capture (so you can trade off detail versus storage requirements). You can also configure different user IDs into the system (so that the system admin can change settings but the junior network guy can only look at data). The Filter Setup item lets you force the inclusion or exclusion of traffic to and from specified ports and IP addresses. The data log lets you handle historical information that's been recorded in previous sessions and an Upgrade feature will automatically check for new versions of the software. Finally, the Help tab is there to provide context-sensitive assistance should you need it (we found that the only help we really needed was to understand the meaning of the occasional column heading in the data screens – the actual operation of the package is easy to grasp). The final clever thing worth mentioning is that although the interface is implemented as a browser window, you can click on any tab in the display screen to have the system break that tab's information out into a separate window. You can aslo have several of these on the screen at once. It's a neat touch and really enhances the system as it means that as long as you've got the screen space you can have three or four windows open at once and see an overview of the network at a glance. With all the freeware network monitoring packages available, we embarked on this review wondering how anyone could justify charging for what appeared to be a simple network traffic collator. After all, we have an armoury of tools such as OpenNMS and Ethereal, all of which are free and work just great. But then we realised: it's not all that long ago that you'd pay thousands of pounds for a network analyser that doesn't do all that much more than this package does. So $300 is a small price to pay for something so blatantly useful and superbly implemented.


Packages of this type will always form part of a suite of tools for any network manager - you'd use this alongside packet sniffers, application monitoring tools and the like. So don't worry if a particular package doesn't do everything you could possibly want – it's perfectly acceptable to have a collection made up of a modest number of packages that deal with their own task well, and to jump from package to package depending on your requirements.