A method and apparatus controls network bandwidth between a first node and a second node on a network. A data element transmitted from the first node to the second node is intercepted. The data element comprises a data portion and a header portion including an original window size. The original window size in the header portion of the data element is replaced with a replacement window size, the data portion of the data element remaining unmodified. The data element is then routed to the second node, the header portion of the data element being coupled to the replacement window size.