Early Management systems were nothing more than a process of pinging an IP address, when you missed a ping there could be something wrong!
Now we want to know what is wrong and preferable be warned before something goes wrong. And wouldn't it be nice or even required to see who or what is eating up our bandwidth or to have proof that we get the bandwidth we pay for?
All these requirements have led to many protocols and standards over the years. Here is a book that organizes all this, brilliantly.
You can read our extensive review here.