This paper experimentally identifies usage scenarios that trigger IP performance limitations in two common Internet access technologies: DOCSIS cable networks and 802.11b wireless local area networks. We use commercial, standards-compliant implementations of each link technology and demonstrate that data transfers from a remote server to a wireless- or cable-attached client can create substantial latency spikes (upwards of 100ms) on the shared wireless or cable link segment, despite each technology’s generous downstream link bandwidth. These spikes have a significant impact on delay-sensitive applications (such as voice over IP, online games or interactive streaming video) sharing the link. We also observe the negative impact of 802.11bs CSMA/CA on end-to-end TCP performance in the presence of low bandwidth, non-reactive traffic, and DOCSIS request/grant cycle on maximum DOCSIS upstream and downstream bandwidths. We illustrate the former point by calculating the performance degradation of an 802.11b link shared by online game players. Our results should motivate future work on optimized media access algorithms for 802.11b and DOCSIS.