With examples and exercises, this text develops simple models and analyticalmethods from first principles to evaluate performance metrics of various configurations of computer systems and networks. It includes simple, analytically tractable models, such as optimization of saturated CSMA/CD and CSMA/CA LANs; presents models for complex systems as analyzable modifications and/or interconnections of simple models; and contains a wide variety of queuing models, including bursty, MMPP, approximate self-similar traffic, and fluid flow. The author also discusses timing and synchronization in the analysis of discrete time (slotted) networks.