Allied Telesis AT-CM70S - Manual (Page 46)

Chapter 1: Converteon™ Fast Ethernet and Gigabit Ethernet Line Cards
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For these reasons, carriers look for management capabilities at every
layer of the network. The Ethernet layer has not traditionally offered
inherent management capabilities, so the 802.3ah OAM capabilities act as
a first step at providing them. 802.3ah OAM is applicable to the following
Ethernet in the First Mile (EFM) technologies:
ˆ Ethernet in the First Mile over Copper (EFMC)
ˆ Ethernet in the First Mile over Fiber (EFMF)
ˆ Ethernet in the First Mile using Passive Optical Networks (EPON)
Note
Note that these capabilities are not intended to replace SNMP as a
management utilities, but are there to enhance it.
Network operators have the freedom to choose and mix the three EFM
topologies (copper, fiber, or passive optical networking) based on their
business models, network architectures, and subscriber needs. They can
configure and upgrade their access networks with multiple EFM topologies
and manage them with a common set of tools and OAM procedures.
Additionally, EFM OAM is backwards compatible with any existing full-
duplex Ethernet technology, and can be implemented on non-EFM
Ethernet links. This compatibility was facilitated by the decision to use
standard Ethernet frames as the transport mechanism for management
information.
OAM Main Features
Although EFM OAM is compatible with any Ethernet technology and can
be used on even small campus networks, it is geared towards reducing
expenditures for first mile operators. The OAM work of the IEEE 802.3ah
task force addresses three key operational issues when deploying
Ethernet across geographically disparate locations: link performance
monitoring, fault detection and fault signaling, and loopback testing.
ˆ Link Performance Monitoring – Introduces some basic error definitions
for Ethernet so entities can detect failed and degraded connections.
ˆ Fault Detection and Fault Signaling – Provides mechanisms for one
entity to signal another that it has detected an error.
ˆ Loopback Testing – Is often used to troubleshoot networks, allows one
station to put the other station into a state whereby all inbound traffic is
immediately reflected back onto the link.