OAM is enabled on the link. However, the loss of a link or a failure to receive OAMPDUs for five
seconds may cause the discovery process the start over again.
DTEs may be in either active or passive mode. Active mode DTEs instigate OAM communications and
can issue queries and commands to a remote device. Passive mode DTEs generally wait for the peer
device to instigate OAM communications and respond to, but do not instigate, commands and queries.
Rules of what DTEs in active or passive mode can do are discussed in the following sections.
Rules for active mode
A DTE in active mode:
• Initiates the OAM Discovery process
• Sends information PDUs
• May send event notification PDUs
• May send variable request or response PDUs
• May send loopback control PDUs
Exceptions
• A DTE in active mode does not respond to variable request PDUs from DTEs in passive mode
• A DTE in active mode does not react to loopback control PDUs from DTEs in passive mode
Rules for passive mode
A DTE in passive mode:
• Waits for the remote device to initiate the Discovery process
• Sends information PDUs
• May send event notification PDUs
• May respond to variable request PDUs
• May react to received loopback control PDUs
• Is not permitted to send variable request or loopback control OAMPDUs
Remote failure indication
Faults in Ethernet that are caused by slowly deteriorating quality are more difficult to detect than
completely disconnected links. A flag in the OAMPDU allows an OAM entity to send failure conditions
to its peer. The failure conditions are defined as follows:
• Dying gasp: This condition is detected when the receiver goes down. The dying gasp condition is
considered as unrecoverable. The conditions for a dying gasp condition include:
‐
Reload command (Warm reboot)
‐
Boot system flash pri/sec command (Warm reboot)
‐
Failure on the box (Cold reboot)
• Critical event: On any critical event, the DTE will set the critical event bit in the information
OAMPDU. The device will generate critical event in the following cases:
‐
When the temperature of the box breaches the warning/shutdown threshold
‐
Fan failure
Rules for active mode
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FastIron Ethernet Switch Administration Guide
53-1003625-01