Alternative Handshake Mechanism for the Stream Control Transmission Protocol

The Stream Control Transmission Protocol (SCTP) is a message and connection oriented transport protocol using a cookie based four-way handshake for connection establishment. The intention of the four-way handshake is to provide a robust protection against flooding attacks, like TCP SYN-flooding. Although it protects the memory resources on the server side, current implementations require a quite large amount of CPU resources. For some of SCTP's use-cases, like the underlying transport protocol for Web Real-Time Communication (WebRTC) Data-Channels, SCTP's cookie protection is unnecessary and its four-way handshake delays the connection setup unnecessarily.We have developed an alternative handshake method which offers a more lightweight cookie exchange and a zero round-trip time (RTT) connection setup capability while still being fully backwards compatible with the existing handshake procedure. We describe the alternative handshake procedure and its advantages in common use cases like short living connections and WebRTC Data-Channels. In addition, we evaluate the alternative handshake's benefit to the regular handshake with measurements using our FreeBSD kernel implementation.