Foundry NetIron M2404C and M2404F Metro Access Switches
Network Administration Tools (Rev. 03)
Intermediate 802.3ah EFM OAM
© 2008 Foundry Networks, Inc.
Page 58 of 155
Process Overview
•
The discovery process allows a local Data Terminating Entity (DTE) to detect OAM on a
remote DTE. Once OAM support is detected, both ends of the link exchange state and
configuration information (such as mode, PDU size, loopback support, etc.). If both DTEs are
satisfied with the settings, 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 either be in 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/Response PDUs
•
May send Loopback Control PDUs.
•
Exceptions:
•
Does not respond to Variable Request PDUs from DTEs in Passive 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.
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)