IEEE has recently standardized the physical layer and the medium access mechanism for wireless local area networks. This paper presents a performance study of the Distributed coordination function, the fundamental contention based access mechanism. Stochastic Petri nets are used as a modeling formalism.A detailed model captures all relevant system aspects in a concise way. The detailed model is evaluated by simulation and also used to derive two more compact models which are analytically tractable. All models are used to investigate different physical layer options and the influence of several system parameters.