Packet loss is a major problem for real-time Internet applications. Markov models of packet loss are often used to develop and evaluate the performance of these applications. Despite their wide use, these models have not been validated in terms of how well they capture the loss conditions experienced by residential Internet users. We evaluate the accuracy of common packet loss models using traces of IPTV-like traffic measured on residential ADSL and Cable links, and find that these models are insufficient to capture the observed packet loss patterns. We introduce a new type of model, incorporating packet delay information, and show improved accuracy over previous models.