Apple Inc. Google Switzerland GmbH Karlstad University University of Aberdeen University of Glasgow This document describes an architecture for exposing transport protocol features to applications for network communication. This system exposes transport protocol features to applications for network communication. The Transport Services Application Programming Interface (API) is based on an asynchronous, event-driven interaction pattern. This API uses messages for representing data transfer to applications, and describes how a Transport Services Implementation can use multiple IP addresses, multiple protocols, and multiple paths, and provide multiple application streams. This document provides the architecture and requirements. It defines common terminology and concepts to be used in definitions of a Transport Service API and a Transport Services Implementation.