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Information OAM PDU Components
Transmission Settings for Information OAM PDUs
Copyright © 2010, Juniper Networks, Inc.
the customer edge (CE) devices are normally configured for passive mode operation,
whereas the provider edge (PE) equipment is configured for active mode operation.
An OAM entity in active mode initiates the discovery process by sending an Information
OAM PDU to the slow protocols multicast address (destination MAC address of the
remote entity) at a configured rate. The transmitted Information OAM PDU contains a
local-information type-length-value (TLV). This TLV contains the following fields:
State—Transmission or receiving state for forwarded packets. The mode can be either
active or passive and can be used to determine device functionality.
Capabilities of the OAM sublayer—Advertises the capabilities of the local OAM entity.
With this information a peer can determine what functions are supported and
accessible, such as loopback or unidirectional operation. This field also specifies the
maximum OAM PDU size for receipt and delivery. This information, together with the
rate limiting value of 10 frames per second, can be used to specify the bandwidth
allocated to OAM traffic.
Vendor OUI—Organization unique identifier (OUI), which is controlled by the IEEE and
is typically the first three bytes of a MAC address.
Vendor-specific information—A 32-bit identifier, which is used to distinguish the type
of platform in conjunction with the vendor OUI field.
After a local entity sends an Information OAM PDU, the remote OAM entity waits to
receive the local information of the peer. After receipt of the Information OAM PDU, the
OAM entity applies a policy to determine whether an OAM relationship can be established.
For example, loopback mode might be required for the OAM association to be completed.
If the remote entity does not support loopback, the local entity might disable the OAM
association.
After an OAM association is established, Information OAM PDUs are sent at a configured
rate. If no OAM PDUs other than Information OAM PDUs are available to be sent from
the local peer to the remote peer, the local entity sends Information OAM PDUs that
contain both the local and remote information TLVs. This constant bidirectional transfer
of Information OAM PDUs serves as a keepalive mechanism for the OAM association. If
no Information OAM PDUs are received within 5 seconds, the discovery process restarts
and a link-fault event is generated that might cause a transition in the operational status
of the Ethernet interface to the down state. If the OAM association with the peer is
reestablished, OAM clears the link-fault event to cause a transition of the interface to
the operational up state. The operational status of an interface does not depend only
on the OAM status. Other factors, such as the administrative state of the interface, also
impact the operational state.
You can configure the OAM discovery function in JunosE Software per Ethernet major
interface as either active or passive mode. The OAM state machine labels a port to be in
the operational down state until the discovery process is completed successfully. You
can configure the PDU timer, which is the rate at which Information OAM PDUs are sent
to the remote peer to keep the OAM association active, in the range of milliseconds with
Chapter 7: Configuring IEEE 802.3ah OAM Link-Fault Management
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