Quite often we are asked to find the source of speed problems on customer's networks. Most are small businesses that do not have any kind of advanced router that gives any kind of detail on what is happening on the network at any given time, nor the ability to monitor anything.
What I am wondering is what people are using that works well to monitor just this sort of network problem? We would like something that is inexpensive and preferably open-source.
I am not opposed to building a dedicated box for something like this. In fact my preference would be to use a Debian based Linux box for something like this. We frequently setup this type of server and are quite familiar with the usage.