Multipath TCP (MPTCP) is an experimental protocol currently under standardization in the IETF. MPTCP allows to use multiple TCP connections for one data transmission if at least one of the endpoints is multi-homed. For example, this can be a mobile device with a Wifi and a 3G interface. It is assumed that the paths are disjoint or partly disjoint. As such these paths have different transmission characteristics, like speed or delay. With MPTCP the congestion control of each single TCP transmission is coupled in such a way that the transmission data is distributed over all subpaths depending on the load situation on each path. In this paper, we present our implementation of the MPTCP congestion control algorithm in the Linux kernel. We evaluated, based on simulations that use the real Linux kernel implementation, if the intended goals on resource pooling and sharing could be reached.