Abstract: This paper describes a new IP transport protocol,the stream control transmission protocol(SCTP),which is at an equivalent layer as UDP(User Datagram Protocol) and TCP(Transmission Control Protocol) and especially fit for signaling messages transmission such as multimedia data over IP networks.The infrastructure of the SCTP which enables a reliable transport service through an connection-oriented mechanism is introduced,and the core features of the SCTP,multi-streaming and multi-homing are discussed.In addition,the SCTP message format,state machine and the three main phases in states transferring,and the specific mechanisms to obtain appropriate congestion avoidance and resistance to flooding and masquerade attacks during these phases are analyzed.Finally,the details of the implementation of SCTP are presented.