Allied Telesis AT-CM70S - Manual (Page 47)

Converteon Media Converter Line Cards Reference Guide
47
OAM Protocol
The operation of OAM on an Ethernet interface does not adversely affect
data traffic as OAM is a slow protocol with very limited bandwidth potential,
and it is not required for normal link operation. This slow protocol can be
implemented in hardware or software, ensuring media independence. By
utilizing the slow protocol MAC address, OAM frames are intercepted by
the MAC sublayer and cannot propagate across multiple hops in an
Ethernet network. This implementation assures that OAM Protocol Data
Units (OAMPDUs) only affect the operation of the OAM protocol itself and
not user data traffic.
OAMPDU Types
The architecture of the OAM protocol is based on OAMPDU, which are
exchanged between two Ethernet ports. OAMPDUs are normal Ethernet
frames that use a specific multicast destination address and EtherType.
Most of the OAMPDU types also define a set of standard type-length-value
(TLV) encoding of attributes within the type.
ˆ Information OAMPDUs
Information OAMPDUs are used for discovery; they are variable-length
OAMPDUs.
The different TLVs for Information PDUs are Local Information,
Remote Information, and Organizational Specific.
Local and Remote Information is used in the discovery process. The
Organizational Specific Information TLV is used for vendor extensions.
It is encoded here because the source MAC address is not a simple
indication of organization identification as many organizations have
multiple OUIs assigned. The 32-bit vendor specific information is not
defined and is used to encode the model or version of the platform.
The platform identity held is intended to allow simple identification of
the hardware device.
ˆ Event OAMPDUs
The data field in the Event OAMPDUs contains one or more link event
TLVs. This variable-length PDU is used for link monitoring.
The link event TLVs may be sent multiple times to increase the
likelihood of reception (for example, in the case of high bit-errors).
These TLVs may include a time reference when generated.
ˆ Loopback Control OAMPDUs
The Loopback Control OAMPDU provides the loopback command.
ˆ Variable Request/Response OAMPDUs
The variables accessible through OAM must be in the Ethernet branch
of the MIB tree. The process of variable retrieval involves transferring
Ethernet counters and statistics via Variable Containers/Descriptors.