An example system for Transmission Control Protocol (TCP) window sizing is disclosed. The example disclosed herein comprises a data flow detection engine, a TCP connection engine, a feedback engine, and a TCP window sizing engine. The data flow detection engine is to detect the number of data flows received by a buffer from a network component. The TCP connection engine is to determine a number of TCP connections within the network component from the number of data flows. The feedback engine is to send a feedback signal to a source of at least one of the number of TCP connections based on a state of the buffer and the number of TCP connections. The TCP window sizing engine is to adjust a TCP window size based on the feedback signal.