H3C Technologies H3C S7500E Series Switches - Manual (Page 37)

2-4
2) An unregistered ONU responds to the discovery GATE message and modifies its local clock to be
consistent with the time stamp contained in the GATE message. When the local clock of the ONU
reaches the start time of the discovery timeslot, the ONU waits a random period of delay before
sending a REGISTER_REQ message, which contains the MAC address of the ONU and the local
time stamp of the ONU when the REGISTER_REQ message is sent.
3) Upon receiving the REGISTER_REQ message from the unregistered ONU, the OLT obtains the
ONU's MAC address and ONU-OLT round trip time (RTT) (For the RTT measurement, see
Configuring the maximum ONU-OLT RTT . The ONU-OLT RTT is mainly used for the time
synchronization between an OLT and ONUs.
4) The OLT parses the received REGISTER_REQ message, and uses the MAC address contained
in the message to unicast a REGISTER message to the unregistered ONU. The REGISTER
message contains a Logical Link ID (LLID) assigned to the ONU as the unique identifier of the
ONU.
5) Right after sending a REGISTER message, the OLT sends a general GATE message to the same
ONU.
6) After receiving the REGISTER message and general GATE message, the ONU sends a
REGISTER_ACK message in the timeslot assigned in the GATE message to notify the OLT that
the REGISTER message is parsed successfully.
7) The ONU registration is complete.
Extended OAM Connection Establishment
The EPON cards of the S7500E series Ethernet switches support the Operation, Administration and
Maintenance (OAM) functions and extended OAM functions. This enables OLTs to remotely operate,
manage, and maintain ONUs.
Extended OAM connection establishment includes OAM capability discovery and exchange of
additional information. It is the capability acknowledgement process required before completing other
extended OAM functions. Data transmission begins only after the extended OAM connection is
established. The process of extended OAM connection establishment is as follows:
1) Standard OAM discovery establishment is complete.
2) The ONU reports the supported Organizationally Unique Identifier (OUI) and extended OAM
version number to the OLT.
3) The OLT checks whether the reported OUI and extended OAM version number are in the list of
OUIs and extended OAM version numbers supported by the OLT:
If yes, the extended OAM connection for the ONU is established successfully;
Otherwise, the extended OAM connection for the ONU cannot be established.
For detailed OAM and extended OAM descriptions, refer to the Ethernet OAM Configuration and
Extended OAM Configuration in the High Availability Configuration Guide.