Toward a Composable Transport: Separating Loss Detection from Retransmission

Transport protocols are traditionally designed and implemented as a monolithic entity. As a result, it is extremely di cult for researchers to modify a small portion of it and evaluate it independently. This barrier encourages the re-use of existing transport protocols out of convenience even when performance is sub-optimal. In this paper, we explore the challenges of separating di erent transport functions into individual pieces. Speci cally, we investigate the separation of loss detection from automatic retransmission in a transport protocol. We propose an architecture to logically separate loss detection, congestion control, and automatic repeat request(ARQ). We implemented a simple experimental framework to allow researchers to mix and match di erent acknowledgment schemes, congestion control algorithms, and retransmission schemes. The fundamental challenge here is to separate loss detection from loss action. A special ack scheme using ack vector is proposed to detect losses for unreliable ows.