Brocade Multi-Service IronWare Administration Guide (Supporting R05.6.00) - Manual (Page 209)

Multi-Service IronWare Administration Guide 191
53-1003028-02
IEEE 802.3ah EFM-OAM
6
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
Link monitoring process
The Link Monitoring Process is used for detecting and indicating link faults under a variety of
circumstances. Link monitoring uses the Event Notification OAMPDU, and sends events to the
remote OAM entity when there are problems detected on the link. The error events defined in the
standard are:
• Errored Symbol Period (errored symbols per second): the number of symbol errors that
occurred during a specified period exceeded a threshold. These are coding symbol errors (for
example, a violation of 4B/5B coding).
• Errored Frame (errored frames per second): the number of frame errors detected during a
specified period exceeded a threshold.
• Errored Frame Period (errored frames per N frames): the number of frame errors within the last
N frames has exceeded a threshold.
• Errored Frame Seconds Summary (errored secs per M seconds): the number of errored
seconds (one second intervals with at least one frame error) among the last M seconds has
exceeded a threshold.
Since 802.3ah OAM does not guarantee the delivery of OAMPDUs, the Event Notification OAMPDU
(discussed in the OAMPDU section below) can be sent multiple times to reduce the probability of
losing notifications. A sequence number is used to recognize duplicate events. The Link Monitoring
Process operates for all the links on which EFM OAM is enabled.
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:
• Link Fault: The Link Fault condition is detected when the receiver loses the signal. This
condition is sent once per second in the Information OAMPDU.
• Dying Gasp: This condition is detected when the receiver goes down. The Dying Gasp condition
is considered as unrecoverable. Conditions for dying gasp:
• Reload or reset from MP
• Interface disable (admin shutdown)
• Link-OAM disable on interface (deconfiguration)
• Crash on the box
• Device power down (incidental or deliberate).