France Telecom France Telecom This document specifies an extension to minimize the delay induced by the presence of MPTCP-unfriendly nodes in some of the paths selected by a MPTCP endpoint, and which may support the establishment of MPTCP subflows. Concretely, this procedure allows a MPTCP endpoint to assess whether the networks the endpoint connects to are compliant with MPTCP signals or not. The procedure is not enabled for every new MPTCP connection; it is activated upon bootstrap or when a network attachment change occurs (e.g., attach to a new network, discover a new external IP address, etc.).