The end-to-end nature of today’s transport protocols is increasingly being questioned by the growing heterogeneity of networks and devices, and the need to support in-network services. To address these challenges, we present Tapa, a transport architecture that systematically combines two concepts. First, it unbundles today’s transport such that network speciﬁc functions (e.g., congestion control) are implemented on a per-segment basis, where a segment spans a part of the end-to-end path that is homogeneous (e.g., wired Internet or an access network) while functions that relate to application semantics (e.g., data ordering) are still implemented end-to-end. Second, it has an explicit notion of in-network services (e.g., caching, opportunistic content retrieval, etc) that can be supported while maintaining precise end-to-end application semantics. In this paper, we present the basic design, implementation and evaluation of Tapa. We also present diverse case studies that show how Tapa can easily support opportunistic content retrieval in online social networks, various mobile and wireless optimizations, and an in-network energy saving service that improves battery life of mobile devices.