Foundry NetIron M2404C and M2404F Metro Access Switches
Network Administration Tools (Rev. 03)
Intermediate 802.3ah EFM OAM
© 2008 Foundry Networks, Inc.
Page 59 of 155
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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:
Management of the
reload
command.
Device power down (incidental / deliberate).
•
Critical Event:
When a critical event occurs, the device is
unavailable as a result of
malfunction
, and it is to be restarted by the user. The critical events can be sent immediately
and continually. Conditions for critical events:
Fatal error mess any task on the device (suspend)
When the dying gasp or critical event occurs, the device driver will call a special API in the EFM-
OAM implementation.
The link fault applies only when the physical sublayer is capable of independent transmission and
reception.
When a link receives no signal from its peer at the physical layer (for example, if the peer laser is
malfunctioning), the local entity sets this flag to let the peer know that its transmit path is
inoperable. The link-down API will be called by the device driver in order to notify the remote
device of the link fault.
Since the above conditions are severe, when they are set in the flag, the OAMPDU is not subject to
normal rate limiting policy.
Remote Loopback
An OAM entity can put its remote entity into loopback mode using a loopback control OAMPDU.
This helps users ensure quality of links during installation or when troubleshooting. In loopback
mode, each frame received is transmitted back on that same port except for OAMPDUs and pause
frames. The periodic exchange of OAMPDUs must continue while in the loopback state to