H3C Technologies H3C SR8800 - Manual (Page 19)

10
How Ethernet OAM works
This section describes the working procedures of Ethernet OAM.
Ethernet OAM connection establishment
Ethernet OAM connection is the basis of all the other Ethernet OAM functions. OAM connection
establishment is also known as the “Discovery phase”, where an Ethernet OAM entity discovers remote
OAM entities and establishes sessions with them.
In this phase, interconnected OAM entities determine whether Ethernet OAM connections can be
established, by exchanging Information OAMPDUs to notify the peer of their OAM configuration
information and the OAM capabilities of the local nodes. An Ethernet OAM connection can be
established between entities that have matching Loopback, link detecting, and link event settings. After
an Ethernet OAM connection is established, Ethernet OAM takes effect on both sides.
For Ethernet OAM connection establishment, a router can operate in active Ethernet OAM mode or
passive Ethernet OAM mode, but a router role will be somewhat different depending on the mode.
Table 6 Active Ethernet OAM mode and passive Ethernet OAM mode
Item Active Ethernet OAM mode Passive Ethernet OAM mode
Initiating OAM Discovery Available Unavailable
Responding to OAM Discovery Available Available
Transmitting Information
OAMPDUs
Available Available
Transmitting Event Notification
OAMPDUs
Available Available
Transmitting Information
OAMPDUs without any TLV
Available Available
Transmitting Loopback Control
OAMPDUs
Available Unavailable
Responding to Loopback Control
OAMPDUs Available—if both sides operate in
active OAM mode
Available
NOTE:
•
Only OAM entities operating in active OAM mode can initiate OAM connections, and those operating
in passive mode wait and respond to the connection requests sent by their peers.
• No OAM connection can be established between OAM entities operating in passive OAM mode.
After an Ethernet OAM connection is established, the Ethernet OAM entities on both sides exchange
Information OAMPDUs at a specified interval—handshake packet transmission interval—to check
whether the Ethernet OAM connection is normal. If an Ethernet OAM entity receives no Information
OAMPDU within the Ethernet OAM connection timeout time, the Ethernet OAM connection is considered
disconnected.
Link monitoring
Error 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
indicate link faults in various environments. Ethernet OAM implements link monitoring through the
exchange of Event Notification OAMPDUs. When detecting one of the link error events listed in Table 7 ,