6
when the settings for loopback, link detecting, and link event of both sides match. After an Ethernet OAM
connection is established, Ethernet OAM takes effect on both sides.
For Ethernet OAM connection establishment, a device can operate in active Ethernet OAM mode or
passive Ethernet OAM mode.
Table 6 Active and passive Ethernet OAM modes
Passive Ethernet OAM mode
Responding to OAM Discovery
Transmitting Information
OAMPDUs
Transmitting Event Notification
OAMPDUs
Transmitting Information
OAMPDUs without any TLV
Transmitting Loopback Control
OAMPDUs
Responding to Loopback Control
OAMPDUs
Available—if both sides operate
in active OAM mode
NOTE:
OAM connections can be initiated only by OAM entities operating in active OAM mode. OAM entities
operating in passive mode wait and respond to the connection requests sent by their peers.
No OAM connection can be established between OAM entities operating in passive OAM mode.
After an Ethernet OAM connection is established, the Ethernet OAM entities on both sides exchange
Information OAMPDUs at a specified interval—handshake packet transmission interval—to check whether
the Ethernet OAM connection is normal. If an Ethernet OAM entity receives no Information OAMPDU
within the Ethernet OAM connection timeout time, the Ethernet OAM connection is considered
disconnected.
Link monitoring
Error detection in an Ethernet is difficult, especially when the physical connection in the network is not
disconnected but network performance is degrading gradually. Link monitoring is used to detect and
indicate link faults in various environments. Ethernet OAM implements link monitoring through the
exchange of Event Notification OAMPDUs. When detecting a link error event listed in Table 7, the local
OAM entity sends an Event Notification OAMPDU to notify the remote OAM entity. With the log
information, network administrators can keep track of network status promptly.
Table 7 Ethernet OAM link error events
An errored symbol event occurs when the number of
detected symbol errors over a specific detection
interval exceeds the configured threshold.
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