Telltale Twin: Mutual Information in Multipath TCP Subflows

Multipath Transmission Control Protocol (MPTCP) creates multiple subflows using the available network interfaces of the device to provide a single network connection between the two hosts. Each subflow is a TCP connection and MPTCP uses TCP options field to communicate the control signals related to the MPTCP operations. MPTCP exposes single TCP connection to the application and multiplexes traffic to the subflows based on their path characteristics. Therefore, the subflow characteristics are interrelated. We hypothesise that by observing one subflow, the network related information of the unseen subflow can be inferred. A set of experiments were conducted to test this hypothesis on MPTCP connections with two subflows using the Mininet network emulator. We demonstrated that there is a strong correlation between the data flow characteristics of the two subflows. Therefore, it is possible to elicit flow information of a subflow by observing the other subflow.