5-3Table 5-2 Functions of different types of OAMPDUsOAMPDU type FunctionInformationOAMPDUUsed for transmitting state information of an Ethernet OAM entity (including theinformation about the local device and remote devices, and customizedinformation) to the remote Ethernet OAM entity and maintaining OAMconnectionsEventNotificationOAMPDUUsed by link monitoring to notify the remote OAM entity when it detectsproblems on the link in between.LoopbackControlOAMPDUUsed for remote loopback control. By inserting the information used toenable/disable loopback to a loopback control OAMPDU, you canenable/disable loopback on a remote OAM entity.How Ethernet OAM WorksThis section describes the working procedures of Ethernet OAM.Ethernet OAM connection establishmentEthernet OAM connection is the base of all the other Ethernet OAM functions. OAM connectionestablishment is also known as the Discovery phase, where an Ethernet OAM entity discovers remoteOAM entities and establishes sessions with them.In this phase, interconnected OAM entities notify the peer of their OAM configuration information andthe OAM capabilities of the local nodes by exchanging Information OAMPDUs and determine whetherEthernet OAM connections can be established. An Ethernet OAM connection can be established onlywhen the settings concerning Loopback, link detecting, and link event of the both sides match. After anEthernet OAM connection is established, Ethernet OAM takes effect on it.As for Ethernet OAM connection establishment, a device can operate in active Ethernet OAM mode orpassive Ethernet OAM mode. Table 5-3 compares active Ethernet OAM mode with passive EthernetOAM mode.Table 5-3 Active Ethernet OAM mode and passive Ethernet OAM modeItem Active Ethernet OAM mode Passive EthernetOAM modeInitiating OAM Discovery Available UnavailableResponding to OAM Discovery Available AvailableTransmitting Information OAMPDUs Available AvailableTransmitting Event NotificationOAMPDUs Available AvailableTransmitting Information OAMPDUswith the Data/Pad field being empty Available AvailableTransmitting Loopback ControlOAMPDUs Available UnavailableResponding to Loopback ControlOAMPDUsAvailable (if both sidesoperate in active OAM mode) Available
