An ONU sends an Acknowledge (ACK) message to the OLT to indicate that it successfully received a downstream message from it. An
ONU that doesn’t send back an ACK message can be experiencing problems or might be too busy to immediately respond to the request.
C.2.9 Con
fi
gure_port-ID Message: Downstream
This message assigns a GEM port-ID to the ONU’s OMCC.
C.2.10 Encrypted_port-ID Message: Downstream
This message can be issue at any time. It indicates to ONUs which channels are encrypted or not.
C.2.11 BER Interval Message: Downstream
This message defines the time interval for the ONU(s) to accumulate downstream bit errors. After receiving the message, the ONU starts
a timer and accumulates downstream errors until the interval time is met.
C.2.12 REI (Remote Error Indication) Message: Upstream
The ONU sends an upstream REI message with the number of recorded bit errors after each BER
interval.
C.2.13 Request_key Message (Downstream) and Encryption_key Message (Upstream)
The OLT requests the ONU to generate a new encryption key and send it in an encryption_key message. This encryption_key message
is sent three times.
C.2.14 Key_switching_time Message: Downstream
After requesting a new key from one or all ONUs, the OLT sends the key_switching_time message. This instructs the ONU when to
switch keys. The OLT sends three key requests. For each key switching message received, the ONU responds with an acknowledge
message.
C.2.15 No_message Message: Both Directions
As defined in the G-PON frame structure, the OLT sends a PLOAM message downstream unconditionally in every frame. If the message
queue is empty, the OLT sends a No_message message.
The same is true in the upstream direction. An ONU will send a No_Message message if its message queue is empty and the OLT grants
a PLOAM slot to it.
C.2.16 Popup Messages
A loss of downstream signal or loss of synchronization will cause a G.984 G-PON ONU to enter popup state.
If it recovers the downstream signal before a timer expires (recommended value 100 ms), and if the OLT is quick enough to recognize the
loss and respond to it, the popup message may bring the ONU back into operation state without taking it through the reranging process.
Downstream, Broadcast
The broadcast form of this message causes all ONUs in popup state to move into ranging state. ONUs not in popup state ignore the
message.
C.2.17 Deactivate_ONU-ID Message: Downstream
ONUs that receive this message stop transmitting upstream and move to standby state. In standby state, the ONU responds to serial
number grants, is recognized by the OLT, and is reactivated into the PON.
C.2.18 Disable_serial_number Message: Downstream
An OLT will send this message with the disable option to attempt to deactivate a potential rogue ONU. The disable option moves the ONU
to the Emergency Stop state and turns off its laser. In emergency state, the ONU is banned from sending data upstream. Once the
deactivated ONU’s malfunction is fixed, the OLT may reactivate the ONU, sending a Disable_Serial_Number message with the enable
option. This moves the ONU to Standby state.
C.2.19 Dying_gasp Message: Upstream
MTTplus-420_User_Manual_RevC00
Page 74 of 75
