It is designed to aggressively adjust the sender's congestion window to optimise TCP for connections with large bandwidth-delay products while trying not to harm fairness (as can occur with HSTCP).
In particular, when queuing is detected, the delay-based window is reduced by the estimated queue size to avoid the problem of "persistent congestion" reported for FAST and Vegas.
[citation needed] Descriptions of Compound TCP can be found in a conference paper,[2] an Internet-Draft,[3] and a US patent.
[1] The following registry key can be set to 1 to enable, or 0 to disable: CTCP is enabled by default in computers running beta versions of Windows Server 2008 and disabled by default in computers running Windows Vista and 7.
A patch derived from this was developed at Caltech, which included CTCP's TUning By Emulation (TUBE, and only released to researchers due to software patents.