In order to increase the performance of TCP ( Transport Control Protocol) in networks with long propagation delay and high link error rates, detection unit scheme, an active and self_ adaptive scheme, has been involved in many implementations for TCP improvement. 为提高TCP协议在长时延、高差错率网络中的性能,探测元机制做为一种主动自适应机制,在TCP的许多改进实现中被涉及。