OAM connections can be initiated only by OAM entities operating in active OAM mode, while those
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 periodically to keep the Ethernet OAM connection valid. If an Ethernet OAM
entity receives no Information OAMPDU for five seconds, the Ethernet OAM connection is
The interval to send Information OAMPDUs is determined by a timer. Up to ten Information OAMPDUs
can be sent in a second.
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. Upon detecting a link error event listed in
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 in time.
Table 1-4 Ethernet OAM link error events
Ethernet OAM link events
Errored symbol event
Errored frame event
Errored frame period event
Errored frame seconds event
An errored symbol event occurs when the number of detected
symbol errors over a specific detection interval exceeds the
An errored frame event occurs when the number of detected
error frames over a specific interval exceeds the predefined
An errored frame period event occurs if the number of frame
errors in specific number of received frames exceeds the
When the number of error frame seconds detected on a port over
a detection interval reaches the error threshold, an errored frame
seconds event occurs.