Figure 10.1: OAM location in OSI model
OAM entity receives no Information OAMPDU for five seconds, the Ethernet OAM connection is
disconnected.
10.1.2 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 cod-
ing 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.)
Errored frame event: The number of detected error frames over M seconds can not be less
than the low threshold.
Errored frame seconds event: The number of error frame seconds detected over M seconds
can not be less than the low threshold. (Errored frame second: Receiving an errored frame at
least in a second.)
77
To Next Page
Loading...
General