PLANET XGS3-24042 - Manual (Page 117)

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Chapter 14 EFM OAM Configuration
14.1 Introduction to EFM OAM
Ethernet is designed for Local Area Network at the beginning, but link length and network scope is extended
rapidly while Ethernet is also applied to Metropolitan Area Network and Wide Area Network along with
development. Due to lack the effectively management mechanism, it affects Ethernet application to
Metropolitan Area Network and Wide Area Network, implementing OAM on Ethernet becomes a necessary
development trend.
There are four protocol standards about Ethernet OAM, they are 802.3ah (EFM OAM), 802.3ag (CFM), E-LMI
and Y.1731. EFM OAM and CFM are set for IEEE organization. EFM OAM works in data link layer to validly
discover and manage the data link status of rock-bottom. Using EFM OAM can effectively advance
management and maintenance for Ethernet to ensure the stable network operation. CFM is used for
monitoring the whole network connectivity and locating the fault in access aggregation network layer.
Compare with CFM, Y.1731 standard set by ITU (International Telecommunications Union) is more powerful.
E-LMI standard set by MEF is only applied to UNI. So above protocols can be used to different network
topology and management, between them exist the complementary relation.
EFM OAM (Ethernet in the First Mile Operation, Administration and Maintenance) works in data link layer of
OSI model to implement the relative functions through OAM sublayer, figure is as bleow:
OSI Model
Application
Presentation
Session
Transport
Network
Data Link
Physical
Higher layers
LLC
OAM(Optional)
MAC
Physical Layer
LAN
CSMA/CD
Layers
Figure 14-1 OAM location in OSI model
OAM protocol data units (OAMPDU) use destination MAC address 01-80-c2-00-00-02 of protocol, the max
transmission rate is 10Pkt/s.
EFM OAM is established on the basis of OAM connection, it provides a link operation management
mechanism such as link monitoring, remote fault detection and remote loopback testing, the simple
introduction for EFM OAM in the following:
1. Ethernet OAM connection establishment
Ethernet OAM entity discovers remote OAM entities and establishes sessions with them by exchanging
Information OAMPDUs. EFM OAM can operate in two modes: active mode and passive mode. One session
can only be established by the OAM entity working in the active mode and ones working in the passive mode