Table of Contents

Chapter 1 OAM Configuration. 1-1

1.1 OAM Overview. 1-1

1.1.1 Types of OAMPDUs. 1-1

1.1.2 OAM Connection Establishment 1-2

1.1.3 OAM Standards. 1-5

1.2 OAM Configuration Task List 1-5

1.3 Configuring Basic OAM Functions. 1-5

1.4 Configuring Link Monitoring. 1-6

1.5 Enabling OAM Loopback Testing. 1-7

1.6 Displaying and Maintaining OAM Configuration. 1-8

1.7 OAM Configuration Example. 1-9

 

Chapter 1  OAM Configuration

When configuring the OAM function, go to these sections for information you are interested in:

l           OAM Overview

l           OAM Configuration Task List

l           Configuring Basic OAM Functions

l           Configuring Link Monitoring

l           Enabling OAM Loopback Testing

l           Displaying and Maintaining OAM Configuration

l           OAM Configuration Example

1.1  OAM Overview

Ethernet OAM (operations, administration, and maintenance) is a tool monitoring Layer-2 link status by sending OAM protocol data units (OAMPDUs) between devices. It helps network administrators manage their networks effectively.

Currently, Ethernet OAM is mainly used to address common link-related issues on the “last mile.” By enabling Ethernet OAM on two devices connected by a point-to-point connection, you can monitor the status of the link. Ethernet OAM provides the following functions:

l           Link performance monitoring, for detecting link errors

l           Fault detection and alarm, for reporting link errors to the administrators

l           Loopback testing, for detecting link errors through non-OAMPDUs

1.1.1  Types of OAMPDUs

Figure 1-1 shows the format of different types of OAMPDUs.

Figure 1-1 The format of different types of OAMPDUs

The fields in an OAMPDU are described as follows.

Table 1-1 Description of the fields in an OAMPDU

Field	Description	Value
Dest addr	Destination MAC address of the Ethernet OAMPDU	Multicast MAC address 0180c2000002
Source addr	Source MAC address of the Ethernet OAMPDU	The bridge MAC address of the sending side
Type	Type of the encapsulated protocol in the Ethernet OAMPDU	0x8809
Subtype	The specific protocol being encapsulated in the Ethernet OAMPDU	0x03
Flags	Information about an Ethernet OAM entity	—
Code	Type of the Ethernet OAMPDU	0x00: Information OAMPDU 0x01: Event notification OAMPDU 0x04: Loopback control OAMPDU

 

As mentioned above, Information OAMPDUs, Event Notification OAMPDUs, and Loopback control OAMPDUs are commonly used, which are described as follows.

l           Information OAMPDUs are used for passing the state information about an Ethernet OAM entity (including the information about the local device and remote devices, and customized information) to another Ethernet OAM entity and maintain OAM connections.

l           Event notification OAMPDUs are used for link monitoring. They are sent as an alarm in case a failure occurs to the link connecting the local OAM entity and a remote OAM entity.

l           Loopback control OAMPDUs are used for remote loopback control. By the information in a Loopback control OAMPDU, you can enable/disable loopback on a remote OAM entity.

1.1.2  OAM Connection Establishment

Following are the four OAM functions.

l           OAM connection establishment

l           Link monitoring

l           Remote fault detection

l           Remote loopback testing

Note that OAM connection is the base of all the other Ethernet OAM functions.

I. OAM connection establishment

OAM connection establishment is also known as the Discovery phase, where an OAM entity discovers other OAM entities and sessions between OAM entities are established.

In this phase, interconnected OAM entities notify the peer of their OAM configuration information and the OAM capabilities of the local nodes to support OAM by exchanging Information OAMPDUs and determine whether OAM connections can be established. An OAM connection can be established only when the settings concerning Loopback, link detecting, and link event of the both side match. After an OAM connection is established, OAM takes effect on it.

As for OAM connection establishment, a device can operate in two modes: active OAM mode and passive OAM mode. Only devices operating in active OAM mode can initiate OAM connection establishment processes. Those operating in passive OAM mode, however, wait and respond to OAM connection establishment requests and take corresponding operations. The following table compares active OAM mode with passive OAM mode.

Item	Active OAM mode	Passive 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 with the Data/Pad field being empty	Available	Available
Transmitting Loopback Control OAMPDUs	Available	Unavailable
Responding to Loopback Control OAMPDUs	Available (if both sides operate in active OAM mode)	Available
Transmitting organization-specific OAMPDUs	Available	Available

 

After an OAM connection is established, the OAM entities on both sides exchange Information OAMPDUs periodically to keep the OAM connection valid. If an OAM entity receives no Information OAMPDU for five seconds, the OAM connection is considered invalid. In this case, to enable the OAM entities to communicate with each other again, a new OAM connection is required.

The interval to send Information OAMPDUs is determined by a timer. Up to ten Information OAMPDUs can be sent in a second.

II. Link monitoring

Link monitoring is used to detect and locate link faults in various environments. In OAM, link faults are categorized into link events. OAM implements link monitoring through the exchange of Event Notification OAMPDUs. Upon detecting a link fault, the local device sends an Event Notification OAMPDU to the remote OAM entity to report the fault event. With the log information, network administrators can keep track of network status in time. The following table describes the link events.

OAM link events	Description
Error symbol event	An error signal event occurs when the number of detected signal errors over a specific detection interval exceeds the threshold.
Error frame event	An error frame event occurs when the number of detected error frames over a specific interval exceeds the threshold.
Error frame period event	An error frame period event occurs if the number of frame errors in specific number of received frames exceeds the threshold
Error frame seconds event	When the number of error frame seconds detected on a port over a detection interval reaches the error threshold, an error frame seconds event occurs. (Error frame seconds are the seconds within which error frames are detected.)

 

III. Remote fault detection

Error detection in an Ethernet is difficult, especially when the physical connection in the network is not interrupted but network performance degrades gradually. The flag field defined in OAMPDUs allows an OAM entity to send error information to its peer. It can identify the following link faults.

l           Link Fault: Peer link signal is lost.

l           Dying Gasp: An unexpected fault, such as power failure, occurred.

l           Critical Event: An undetermined critical event happened.

As Information OAMPDUs are sent periodically across OAM connections, an 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.

 

 

IV. Remote loopback testing

Remote loopback testing is available only after the OAM connection is established. With remote loopback enabled, the OAM entity operating in active OAM mode issues remote loopback requests and the peer responds to them. If the peer operates in the loopback mode, it returns all the PDUs to the senders along the original paths.

Performing remote loopback testing periodically helps to detecting network faults in time. Furthermore, performing remote loopback testing by network segments helps to locate network faults.

 

 

1.1.3  OAM Standards

OAM is defined in IEEE 802.3h.

1.2  OAM Configuration Task List

Complete the following tasks to configure OAM:

Task	Remarks
Configuring Basic OAM Functions	Required
Configuring Link Monitoring	Optional
Enabling OAM Loopback Testing	Optional

 

1.3  Configuring Basic OAM Functions

Follow the following steps to configure basic OAM functions:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter Ethernet port view	interface interface-type interface-number	—
Set OAM operating mode	oam mode { active | passive }	Optional The default is active OAM mode.
Enable OAM on the current port	oam enable	Required OAM is disabled by default. After OAM is enabled, the OAM entity tries to establish OAM connection with its peer.

 

 

1.4  Configuring Link Monitoring

Follow these steps to configure the error detection intervals and the error event triggering thresholds that OAM uses for link monitoring:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Configure the error symbol detection interval	oam errored-symbol period period-value	Optional The default is one second.
Configure the error symbol event triggering threshold for an error symbol detection interval	oam errored-symbol threshold threshold-value	Optional The default is 1.
Configure the error frame detection interval	oam errored-frame period period-value	Optional The default is one second.
Configure the error frame event triggering threshold	oam errored-frame threshold threshold-value	Optional The default is 1.
Configure the error frame period detection interval	oam errored-frame-period period period-value	Optional The default is 1,000 milliseconds.
Configure the error frame period event triggering threshold	oam errored-frame-period threshold threshold-value	Optional The default is 1.
Configure the error frame second detection interval	oam errored-frame-seconds period period-value	Optional The default is 60 seconds.
Configure the error frame seconds event triggering threshold	oam errored-frame-seconds threshold threshold-value	Optional The default is 1. This threshold value should not be greater than the corresponding detection interval; otherwise, no error frame second event can be created.

 

To save bandwidth, you can configure OAM to report an error event when the number of errors detected over a specified interval reaches a threshold rather than when an error is detected. For more information about the link monitoring commands in this section, refer to Ethernet OAM Commands in the accompanied command manual.

 

 

1.5  Enabling OAM Loopback Testing

Follow the following steps to enable OAM loopback testing:

To do…	Use the command…	Remarks
Enter system view	system-view	—
Enter Ethernet port view	interface interface-type interface-number	—
Enable OAM loopback testing	oam loopback	Required Disabled by default.

 

 

1.6  Displaying and Maintaining OAM Configuration

To do…	Use the command…	Remarks
Display global OAM configuration	display oam configuration	Available in any view
Display the statistics on critical events after an OAM connection is established	display oam critical-event [ interface interface-type interface-number ]
Display the statistics on OAM link error events after an OAM connection is established or after you clear the statistics	display oam link-event { local | remote } [ interface interface-type interface-number ]
Display the information about an OAM connection	display oam { local | remote } [ interface interface-type interface-number ]
Clear statistics on OAM packets and OAM link error events	reset oam [ interface interface-type interface-number ]	Available in user view only

 

1.7  OAM Configuration Example

I. Network requirements

l           Enable OAM on Switch A and Switch B to manage links on data link layer.

l           Monitor link performance and collect statistics about the error frames received by Switch A.

II. Network diagram

Figure 1-2 Network diagram for OAM configuration

III. Configuration procedure

1)         Configure Switch A

# Configure Ethernet 4/1/2 to operate in passive OAM mode and enable OAM for it.

<Sysname> system-view

[Sysname] interface ethernet 4/1/2

[Sysname-Ethernet4/1/2] oam mode passive

[Sysname-Ethernet4/1/2] oam enable

[Sysname-Ethernet4/1/2] quit

# Set the period for error frame event detection to 20 seconds.

[Sysname] oam errored-frame period 20

# Set the threshold for error frame event detection to 10.

[Sysname] oam errored-frame threshold 10

# Display global OAM configuration.

[Sysname] display oam configuration

Configuration of the errored symbol/frame event window/threshold :

--------------------------------------------------------

Errored-symbol Event period           :     1

Errored-symbol Event threshold        :     1

Errored-frame Event period            :     20

Errored-frame Event threshold         :     10

Errored-frame-period Event period     :     1000

Errored-frame-period Event threshold  :     1

Errored-frame-seconds Event period    :     60

Errored-frame-seconds Event threshold :     1

2)         Configure Switch B

# Configure Ethernet 4/1/2 to operate in active OAM mode (the default OAM mode) and enable OAM for it.

<Sysname> system-view

[Sysname] interface ethernet 4/1/2

[Sysname-Ethernet4/1/2] oam enable

[Sysname-Ethernet4/1/2] quit

# Display OAM link error event statistics.

[Sysname] display oam link-event remote

Port :Ethernet4/1/2

Link Status :Up

OAMRemoteErrFrameEvent : (ms = milliseconds)

---------------------------------------------------------------------

Event Time Stamp          : 5789        Errored FrameWindow   : 10(100ms)

Errored Frame Threshold   : 1           Errored Frame         : 3

Error Running Total       : 35          Event Running Total   : 17

The above information indicates that 35 errors occurred since OAM is enabled on Switch A, 17 of which are caused by error frames. The link is instable.