PLANET WGSW-52040 - Manual (Page 120)

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 need to wait until it receives the connection
request. After an Ethernet OAM connection is established, the Ethernet OAM entities on both
sides exchange Information OAMPDUs continuously to keep the valid Ethernet OAM
connection. If an Ethernet OAM entity receives no Information OAMPDU for five seconds, the
Ethernet OAM connection is disconnected.
2. Link Monitoring
Fault detection in an Ethernet is difficult, especially when the physical connection in the
network is not disconnected but network performance is degrading gradually. Link monitoring
is used to detect and discover link faults in various environments. EFM OAM implements link
monitoring through the exchange of Event Notification OAMPDUs. When detecting a link error
event, the local OAM entity sends an Event Notification OAMPDU to notify the remote OAM
entity. At the same time it will log information and send SNMP Trap to the network
management system. While OAM entity on the other side receives the notification, it will also
log and report it. With the log information, network administrators can keep track of network
status in time.
The link event monitored by EFM OAM means that the link happens the error event, including
Errored symbol period event, Errored frame event, Errored frame period event, Errored frame
seconds event.
Errored symbol period event: The errored symbol number can not be less than the low
threshold. (Symbol: the min data transmission unit of physical medium. It is unique for coding
system, the symbols may be different for different physical mediums, symbol rate means the
changed time of electron status per second. )
Errored frame period event: Specifying N is frame period, the errored frame number within the
period of receiving N frames can not be less than the low threshold. (Errored frame: Receiving
the errored frame detected by CRC.)
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