Transport
       Client                        Converter          Server

        @:C1,C2                        @:Tc                @:S
           ||                            |                  |
           |src:C1     SYN         dst:Tc|src:C1       dst:S|
           |-------MPC [->S:port]------->|-------SYN------->|
           ||                            |                  |
           ||dst:C1                src:Tc|dst:C1       src:S|
           |<---------SYN/ACK------------|<-----SYN/ACK-----|
           ||                            |                  |
           |src:C1                 dst:Tc|src:C1       dst:S|
           |------------ACK------------->|-------ACK------->|
           |                             |                  |
           |src:C2          ...    dst:Tc|       ...        |
           ||<-----Secondary Subflow---->|src:C1       dst:S|
           ||                            |-------data------>|
           |               ..            |    ...           |

Legend:
  Tc: IP address used by the Transport Converter on the internal
      realm.