This document describes an extension to the Stream Control Transmission Protocol (SCTP) [RFC2960] to provide unreliable data transfer services. The benefits of this extension includes unified congestion control over reliable and unreliable data streams, single association for multi-content data services, link level fault tolerance for unreliable data transfer, unreliable data stream multiplexing, etc. The unreliable data transfer service will also support partial payload checksum in order to facilitate bit-error tolerance media applications.