Manual

[phone] www.qtech.ru
Москва, Новозаводская ул., 18, стр. 1
103
3. Remote Fault Detection
In a network where traffic is interrupted due to device failures or unavailability, the flag field
defined in Ethernet OAMPDUs allows an Ethernet OAM entity to send fault information to its
peer. As Information OAMPDUs are exchanged continuously across established OAM
connections, an Ethernet OAM entity can inform one of its OAM peers of link faults through
Information OAMPDUs. Therefore, the network administrator can keep track of link status in
time through the log information and troubleshoot in time.
There are three kinds of link faults for Information OAMPDU, they are Critical Event, Dying
Gasp and Link Fault, and their definitions are different for each manufacturer, here the
definitions are as below:
Critical Event: EFM OAM function of port is disabled.
Link Fault: The number of unidirectional operation or fault can not be less than the high
threshold in local. Unidirectional Operation means unidirectional link can not work normally on
full-duplex link without autonegotiaction. EFM OAM can detect the fault and inform the remote
OAM peers through sending Information OAMPDU.
Dying Gasp: There is no definition present. Although device does not generate Dying Gasp
OAMPDU, it still receives and processes such OAMPDU sent by its peer.
4. Remote loopback testing
Remote loopback testing is available only after an Ethernet OAM connection is established.
With remote loopback enabled, operating Ethernet OAM entity in active mode issues remote
loopback requests and the peer responds to them. If the peer operates in loopback mode, it
returns all packets except Ethernet OAMPDUs to the senders along the original paths.
Performing remote loopback testing periodically helps to detect network faults in time.
Furthermore, performing remote loopback testing by network segments helps to locate
network faults. Note: The communication will not be processed normally in remote loopback
mode.
Typical EFM OAM application topology is in the following, it is used for point-to-point link and
emulational IEEE 802.3 point-to-point link. Device enables EFM OAM through point-to-point
connection to monitor the link fault in the First Mile with Ethernet access. For user, the
connection between user to telecommunication is “the First Mile”, for service provider, it is “the
Last Mile”.