Abstract
The multicast features of the Xpress Transport Protocol (XTP) provide a point-to-multipoint service, which can vary from best-effort to completely reliable. Various proposals have been made for operation with multiple senders, but each of these has some shortcomings. Some extensions to XTP are proposed, which transform it into a multipoint-to-multipoint protocol. These extensions fit naturally with the original design of XTP. An enhanced communications support layer is proposed to provide the mechanisms to permit fully-ordered delivery of packets, and widen XTP's range of applicability to include multi-party interactions requiring high reliability.