Channel-based Unidirectional Stream Protocol (CUSP)

This paper presents a novel transport protocol, CUSP, specifically designed with complex and dynamic network applications in mind. Peer-to-peer applications benefit in particular, as their requirements are met by neither UDP nor TCP. While other modern transports like SCTP or SST have also tried to combine the advantages of TCP and UDP, CUSP overcomes their technical and conceptual shortcomings. CUSP makes it possible to directly express application logic in the message flow. Modern applications need a mixture of request-response, request-multiple-response, publish-subscribe, and message-passing. All of these operations can be conveniently implemented using CUSP’s unidirectional streams. We separate low-level packet management from streams into reusable channels. A channel connects two applications providing negotiation, congestion control, and cryptography. Developers operate on the stream level, sending messages as reliable and ordered byte-streams. Although they may share a common channel, a stall or loss in one stream does not block the others.