An important question for network simulation is what level of detail is required to obtain a desired level of accuracy. While in some networks, the level of detail is an open research issue (for example, radio propagation models in wireless networks), it has long been assumed that wired networks could be accurately modeled by fairly simple queues with a bandwidth limit and propagation delay. To our knowledge this assumption has not been widely tested. In this paper we evaluate different levels of detail for an Ethernet simulation. We consider two models for Ethernet simulation; a detailed, CSMA/CD protocol based model and a more abstract model using a DropTail, shared queue. Using web traffic with two different TCP simulation models, we evaluated the accuracy of these Ethernet models as compared to testbed measurements. We observed the DropTail Ethernet model requires significantly less execution time and can accurately model performance using a bandwidth normalization factor.