Finally, a Use for Componentized Transport Protocols

This paper argues a new relevance for an old idea: decomposing transport protocols into a set of resuable building blocks that can be recomposed in different ways depending on application requirements. We conjecture that point-to-point applications may well be adequately served by the existing suite of monolithic protocol implementations, but widely-distributed peer-to-peer systems such as overlays are not: the design space of transport protocols between nodes in a large, highly coordinated system is much larger. We provide several examples of existing systems that have implemented a diverse range of transport protocols, and show how a building-block approach covers these systems well, enabling simple specification of hybrids and variants of the protocols. In particular, we show how all of our examples can be implemented in the networking stack of P2, a multipurpose system for building overlay networks from declarative specifications.