Multi-Path TCP: revolutionizing connectivity, one path at a time

This post explains how Multi-Path TCP (MPTCP) enables multi-interface connectivity via subflows to support bandwidth aggregation and mobility, detailing Linux and Apple implementations, configuration of path managers and endpoints, and the role of schedulers with future BPF extensibility. It highlights practical caveats such as requirements for recent Linux kernels, NetworkManager support, limitations with server-announced addresses, incompatibility with kTLS, IPv6 ADD-ADDR space constraints when TCP timestamps are enabled, and concludes that the most viable current deployment is Linux servers with iOS/macOS clients in interactive mode, with Linux client usability still maturing.