Specifications

1-12
Cisco MWR 2941 Mobile Wireless Edge Router Software Configuration Guide, Release 12.2(33)MRB
OL-21227-02
Chapter 1 Cisco MWR 2941 Router Overview
Features
• OAM configuration (capabilities)—Advertises the capabilities of the local OAM entity. With this
information a peer can determine what functions are supported and accessible; for example,
loopback capability.
• OAM PDU configuration—Includes the maximum OAM PDU size for receipt and delivery. This
information along with the rate limiting of 10 frames per second can be used to limit the bandwidth
allocated to OAM traffic.
• Platform identity—A combination of an organization unique identifier (OUI) and 32-bits of
vendor-specific information. OUI allocation, controlled by the IEEE, is typically the first three bytes
of a MAC address.
Discovery includes an optional phase in which the local station can accept or reject the configuration of
the peer OAM entity. For example, a node may require that its partner support loopback capability to be
accepted into the management network. These policy decisions may be implemented as vendor-specific
extensions.
Link Monitoring
Link monitoring in Ethernet OAM detects and indicates link faults under a variety of conditions. Link
monitoring uses the event notification OAM PDU and sends events to the remote OAM entity when there
are problems detected on the link. The error events include the following:
• Error Symbol Period (error symbols per second)—The number of symbol errors that occurred
during a specified period exceeded a threshold. These errors are coding symbol errors.
• Error Frame (error frames per second)—The number of frame errors detected during a specified
period exceeded a threshold.
• Error Frame Period (error frames per n frames)—The number of frame errors within the last n
frames has exceeded a threshold.
• Error Frame Seconds Summary (error seconds per m seconds)—The number of error seconds
(1-second intervals with at least one frame error) within the last m seconds has exceeded a threshold.
Because IEEE 802.3ah OAM does not provide a guaranteed delivery of any OAM PDU, the event
notification OAM PDU may be sent multiple times to reduce the probability of a lost notification. A
sequence number is used to recognize duplicate events.
Remote Failure Indication
Faults in Ethernet connectivity that are caused by slowly deteriorating quality are difficult to detect.
Ethernet OAM provides a mechanism for an OAM entity to convey these failure conditions to its peer
via specific flags in the OAM PDU. The following failure conditions can be communicated:
• Link Fault—Loss of signal is detected by the receiver; for instance, the peer's laser is
malfunctioning. A link fault is sent once per second in the information OAM PDU. Link fault
applies only when the physical sublayer is capable of independently transmitting and receiving
signals.
• Dying Gasp—An unrecoverable condition has occurred; for example, a power failure. This type of
condition is vendor specific. A notification about the condition may be sent immediately and
continuously.
• Critical Event—An unspecified critical event has occurred. This type of event is vendor specific. A
critical event may be sent immediately and continuously.