ReP2P Matrix: Decentralized Relays to Improve Reliability and Performance of Peer-to-Peer Matrix

Matrix is a decentralized middleware for low-latency group communication, most renowned for its use in the Element instant messenger. Proposals for peer-to-peer (P2P) Matrix architectures aim to decentralize the current architecture further, which is based on federated servers. These proposals require that the receiver and the originator, or another peer that already successfully received the message, are simultaneously online. We introduce relay-enhanced P2P Matrix (ReP2P Matrix) in order to improve message delivery between peers that are online at different times. The design maintains the advantages of P2P Matrix and integrates well into it, e.g., it reuses existing mechanisms for authentication and authorization. Using an extended real-world group messaging traffic dataset, we evaluate ReP2P Matrix by comparing it to P2P Matrix without relays. The results show that relays do not only improve reliability in message delivery, but also increase the share of low delivery latencies by 50 % points in groups with up to 30 members.