Specifications

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Cisco MWR 2941 Mobile Wireless Edge Router Software Configuration Guide, Release 12.2(33)MRB
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Chapter 1 Cisco MWR 2941 Router Overview
Features
OAM Sublayer
The OAM sublayer presents two standard IEEE 802.3 MAC service interfaces: one facing toward the
superior sublayers, which include the MAC client (or link aggregation), and the other interface facing
toward the subordinate MAC control sublayer. The OAM sublayer provides a dedicated interface for
passing OAM control information and OAM PDUs to and from a client.
The OAM sublayer is made up of three components: control block, multiplexer, and packet parser
(p-parser). Each component is described in the following sections.
Control Block
The control block provides the interface between the OAM client and other blocks internal to the OAM
sublayer. The control block incorporates the discovery process, which detects the existence and
capabilities of remote OAM peers. It also includes the transmit process that governs the transmission of
OAM PDUs to the multiplexer and a set of rules that govern the receipt of OAM PDUs from the p-parser.
Multiplexer
The multiplexer manages frames generated (or relayed) from the MAC client, control block, and
p-parser. The multiplexer passes through frames generated by the MAC client untouched. It passes OAM
PDUs generated by the control block to the subordinate sublayer; for example, the MAC sublayer.
Similarly, the multiplexer passes loopback frames from the p-parser to the same subordinate sublayer
when the interface is in OAM remote loopback mode.
P-Parser
The p-parser classifies frames as OAM PDUs, MAC client frames, or loopback frames and then
dispatches each class to the appropriate entity. OAM PDUs are sent to the control block. MAC client
frames are passed to the superior sublayer. Loopback frames are dispatched to the multiplexer.
Link OAM
Link OAM is defined in the IEEE 802.3ah and IEEE 802.3 Clause 57 standards and provides for
discovery, Link Monitoring, Remote Fault Indication, Remote Loopback, and Cisco proprietary
extensions. The following sections describe Link OAM:
• Discovery
• Link Monitoring
• Remote Failure Indication
• Remote Loopback
• Cisco Vendor-Specific Extensions
• OAM Messages
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.