Specifications

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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
For instructions on how to configure REP, see the “Configuring Resilient Ethernet Protocol (REP)”
section on page 4-15.
Ethernet Operations, Administration, and Maintenance (OAM)
Ethernet Operations, Administration, and Maintenance (OAM) is a protocol for installing, monitoring,
and troubleshooting Ethernet metropolitan-area networks (MANs) and Ethernet WANs. It relies on a
new, optional sublayer in the data link layer of the Open Systems Interconnection (OSI) model. The
OAM features covered by this protocol are Discovery, Link Monitoring, Remote Fault Detection,
Remote Loopback, and Cisco Proprietary Extensions.
The following sections describe the Ethernet OAM features supported on the Cisco MWR 2941:
• Overview
• Link OAM
• Ethernet Connectivity Fault Management (CFM)
• Ethernet Local Management Interface (E-LMI)
Overview
Ethernet OAM is a protocol for installing, monitoring, and troubleshooting metro Ethernet networks and
Ethernet WANs. It relies on a new, optional sublayer in the data link layer of the OSI model. Ethernet
OAM can be implemented on any full-duplex point-to-point or emulated point-to-point Ethernet link. A
system-wide implementation is not required; OAM can be deployed on particular interfaces for part of
a system.
Normal link operation does not require Ethernet OAM. OAM frames, called OAM protocol data units
(PDUs), use the slow protocol destination MAC address 0180.c200.0002. They are intercepted by the
MAC sublayer and cannot propagate beyond a single hop within an Ethernet network.
Ethernet OAM is a relatively slow protocol with modest bandwidth requirements. The frame
transmission rate is limited to a maximum of 10 frames per second; therefore, the impact of OAM on
normal operations is negligible. However, when link monitoring is enabled, the CPU must poll error
counters frequently. In this case, the required CPU cycles will be proportional to the number of
interfaces that have to be polled.
Two major components, the OAM client and the OAM sublayer, make up Ethernet OAM. The following
sections describe these components.
OAM Client
The OAM client is responsible for establishing and managing Ethernet OAM on a link. The OAM client
also enables and configures the OAM sublayer. During the OAM discovery phase, the OAM client
monitors OAM PDUs received from the remote peer and enables OAM functionality on the link based
on local and remote state as well as configuration settings. Beyond the discovery phase (at steady state),
the OAM client is responsible for managing the rules of response to OAM PDUs and managing the OAM
remote loopback mode.