Transmission Control Protocol (TCP) is a communication protocol that is used to provide reliable data delivery between hosts. As TCP is the most highly used transport-layer protocol, many have worked on addressing the issue of performance. Performance issues have been studied in various environments, especially when using 802.11 Wireless Local Area Networks (WLANs). Wireless networks are prone to a higher number of packets loss and corruption. 802.11 WLANs have an equivalently fast acknowledgement mechanism as TCP to ensure reliability of traffic over it. This duplication of functionality between TCP and 802.11 WLAN creates unexpected behaviors that can result in high costs in terms of overall performance. A significant amount of analytical and simulation work has been done in the past to study the behaviour of TCP over 802.11 WLANs. The main contribution of this work is the analysis of TCP interaction in an 802.11 WLAN topology by using real commercial-grade equipments. A testing methodology is designed to do the quantitative performance evaluation in a network topology consisted of wired as well as a wireless connection. The methodology contains test scenarios with different configurable settings on an Access Point (AP) and various controlled impairments in the network topology such as latency, packet drop, noise interference, etc. The performance of TCP is measured in terms of the throughput. This work provides a comprehensive set of experiments to study the behaviour of TCP over 802.11 WLANs. The results can provide insight into the performance cost associated with TCP traffic on 802.11 WLANs under different network environments and configurations on the AP. The results of this work thus have a value to equipment manufacturers and network operators.