Client                                             Server

      /-------------------------------------------\
     |                                             |
     |             Initial Handshake               |
      \-------------------------------------------/


 [Application Data]         -------->
 (epoch=3)

                            <--------      [Application Data]
                                                    (epoch=3)

      /-------------------------------------------\
     |                                             |
     |              Some time later ...            |
      \-------------------------------------------/


 [Application Data]         -------->
 (epoch=3)


 [KeyUpdate]
 (+ update_requested        -------->
 (epoch 3)


                            <--------      [Application Data]
                                                    (epoch=3)


                                                        [ACK]
                            <--------               (epoch=3)


 [Application Data]
 (epoch=4)                  -------->



                            <--------             [KeyUpdate]
                                                    (epoch=3)


 [ACK]                      -------->
 (epoch=4)


                            <--------      [Application Data]
                                                    (epoch=4)