A method and apparatus for adjustment of TCP sliding window with information about network conditions is disclosed. The present invention obtains information from the network below TCP about the condition of the network and traffic and uses this information to control the transmission of the TCP source without any modifications to the existing TCP sources. The invention includes the steps of receiving feedback information in an acknowledgment packet, receiving a packet having an advertised window field set to an original advertised window size for a sliding window, and modifying the advertised window field to chose the size of the sliding window in response to feedback information received in the acknowledgment packet. The original advertised window size indicates the original size of a sliding window for determining a number of bytes that can be sent before an acknowledgment packet is received. The feedback information further includes a window advertisement. The size of the sliding window includes the minimum of the window advertisement and a congestion window. The window advertisement specifies an increase to the size of the sliding window. The increase includes an additional number of octets of data a receiver is prepared to accept. The method further includes the steps of calculating a modified advertised window size using the window advertisement, comparing the modified advertised window size to an original advertised window size and transmitting an acknowledgment including the least of the modified advertised window size and the original advertised window size.