Think it was the Tannebaum Networking book which has a chapter on queuing theory. Couple of lectures on that, only to find the chapter was concluded with something like: "Empirical evidence has shown that network traffic doesn't follow a possion distribution", so was left with a feeling that the chapter was only relevant for exams.

Models based on Poisson distributions are the simplest type of queue from a mathematical point of view. Introductory courses rarely go beyond that.