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Transport aspects                                              2


                          Table 11-25 – ToD frequency synchronization command (sent by the FTU-O)

                                Length
                  Name                         Byte                             Content
                                (bytes)
             ToD phase            5              2         0216 (Note)
             difference
                                              3 and 4      Two bytes representing the superframe count of the t1
                                                           event.
                                              5 and 6      Two bytes representing the ToD phase difference in units of
                                                           2 nanoseconds.
             NOTE – All other values for byte 2 are reserved by ITU-T.
            The FTU-O shall always send the most recent ToD frequency synchronization command and shall discard all
            older ToD frequency synchronization commands.
            NOTE  –  Since  no  response  is  defined,  the  FTU-O  management  entity  will  not  retransmit  the  lost  ToD  frequency
            synchronization command.
            11.2.2.9   Time synchronization command and responses
            The  time  synchronization  commands  and  responses  are  used  to  establish  ToD  phase  synchronization
            between  the  FTU-O  and  the  FTU-R,  as  defined  in  clause  8.5.  The  time  synchronization  command  and
            responses are listed in Table 11-26 (command sent by FTU-O) and Table 11-27 (response sent by FTU-R),
            respectively.  The  command  specified  in  Table  11-26  shall  only  be  sent  by  the  FTU-O.  The  responses
            specified in Table 11-27 shall only be sent by the FTU-R.

            Upon reception of a time synchronization command, the FTU-R may either reject the request to run the
            time synchronization procedure using the reject response defined in Table 11-27 with one of the reason
            codes listed in Table 11-28, or positively acknowledge it by transmitting an ACK response defined in Table
            11-27.
            The first byte of all time synchronization command and responses shall be the command type assigned, as
            shown in Table 11-5 (normal priority commands and responses). The remaining bytes for the commands
            and responses shall be as shown in Table 11-26 and Table 11-27, respectively.


                               Table 11-26 – Time synchronization commands sent by the FTU-O

                               Length
                 Name                         Byte                            Content
                               (bytes)
             ToD(t1)             26            2        0116 (Note 1)
             ToD(t4)                         3 and 4    Two bytes for the superframe count of time stamps ToD(t1) and
             Timestamps                                 ToD(t4).
                                             5 and 6    Two bytes for time synchronization update period expressed in
                                                        superframes.
                                             7 to 12    Six bytes describing the integer portion of the timestamp
                                                        ToD(t1) in units of seconds.
                                            13 to 16    Four bytes describing the fractional portion of the timestamp
                                                        ToD(t1) in units of nanoseconds. (Note 2)


                                            17 to 22    Six bytes describing the integer portion of the timestamp
                                                        ToD(t4) in units of seconds.

                                            23 to 26    Four bytes describing the fractional portion of the timestamp
                                                        ToD(t4) in units of nanoseconds. (Note 2)
             NOTE 1 – All other values for byte 2 are reserved by ITU-T.
                                                      9
             NOTE 2 – The nanosecond portion is always less than 10 .


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