Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Release 3.5 Software Configuration Guide, Cisco IOS Release 15.1(3)MR
OL-26895-01
Chapter 15 Configuring Ethernet OAM, CFM, and E-LMI
Understanding the Ethernet OAM Protocol
– The control block provides the interface between the OAM client and other OAM sublayer
internal blocks.
– The multiplexer manages frames from the MAC client, the control block, and the parser and
passes OAM PDUs from the control block and loopback frames from the parser to the
subordinate layer.
– The parser classifies frames as OAM PDUs, MAC client frames, or loopback frames and sends
them to the appropriate entity: OAM PDUs to the control block, MAC client frames to the
superior sublayer, and loopback frames to the multiplexer.
OAM Features
These OAM features are defined by IEEE 802.3ah:
• Discovery
• Link Monitoring
• Remote Failure Indication
• Remote Loopback
Discovery
Discovery is the first phase of Ethernet OAM and it identifies the devices in the network and their OAM
capabilities. Discovery uses information OAM PDUs. During the discovery phase, the following
information is advertised within periodic information OAM PDUs:
• OAM mode—Conveyed to the remote OAM entity. The mode can be either active or passive and
can be used to determine device functionality.
• 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.