802.3ah Clause 57 (efm-oam) defines the Operations, Administration, and Maintenance (OAM) sublayer, which provides mechanisms useful for monitoring link operation such as remote fault indication and remote loopback control. In general, OAM provides network operators the ability to monitor the health of the network and quickly determine the location of failing links or fault conditions. efm-oam described in this clause provides data link layer mechanisms that complement applications that may reside in higher layers.
OAM information is conveyed in slow protocol frames called OAM protocol data units (OAMPDUs). OAMPDUs contain the appropriate control and status information used to monitor, test and troubleshoot OAM-enabled links. OAMPDUs traverse a single link, being passed between peer OAM entities, and therefore, are not forwarded by MAC clients (like bridges or switches).
The following efm-oam functions are supported:
efm-oam capability discovery
Active and passive modes
Remote failure indication (the handling of critical link events such as link fault, dying gasp, and so on)
Loopback; a mechanism is provided to support a data link layer frame-level loopback mode. Both remote and local loopback modes are supported.
efm-oam PDU tunneling
High resolution timer for efm-oam in 100 ms interval (minimum)
efm-oam link monitoring
Non-zero Vendor Specific Information Field, the 32-bit field is encoded using the format 00:PP:CC:CC and references TIMETRA-CHASSIS-MIB.
00
This must be zeros.
PP
This represents the platform type based on the installed IOM from tmnxHwEquippedPlatform. 7450 ESS deployments may yield different platform values in the same chassis. Because this is IOM-specific, the IOM’s unique hardware ID (tmnxCardHwIndex) must be included to retrieve the correct value.
CC:CC
This represents the chassis type index value from tmnxChassisType which is indexed in tmnxChassisTypeTable. The table identifies the specific chassis backplane.
The value 00:00:00:00 is sent for all releases that do not support the non-zero value or are unable to identify the required elements. There is no decoding of the peer or local vendor information fields on the network element. The hexadecimal value is included in the show port port-id ethernet efm-oam output.
When the efm-oam protocol fails to negotiate a peer session or encounters a protocol failure following an established session the Port State enters the Link Up condition. This port state is used by many protocols to indicate the port is administratively UP and there is physical connectivity but a protocol, such as efm-oam, has caused the ports operational state to enter a DOWN state. A reason code has been added to help discern if the efm-oam protocol is the underlying reason for the Link Up condition.
show port
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Ports on Slot 1
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Port Admin Link Port Cfg Oper LAG/ Port Port Port C/QS/S/XFP/
Id State State MTU MTU Bndl Mode Encp Type MDIMDX
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1/1/1 Down No Down 1578 1578 - netw null xcme
1/1/2 Down No Down 1578 1578 - netw null xcme
1/1/3 Up Yes Link Up 1522 1522 - accs qinq xcme
1/1/4 Down No Down 1578 1578 - netw null xcme
1/1/5 Down No Down 1578 1578 - netw null xcme
1/1/6 Down No Down 1578 1578 - netw null xcme
# show port 1/1/3
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Ethernet Interface
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Description : 10/100/Gig Ethernet SFP
Interface : 1/1/3 Oper Speed : N/A
Link-level : Ethernet Config Speed : 1 Gbps
Admin State : up Oper Duplex : N/A
Oper State : down Config Duplex : full
Reason Down : efmOamDown
Physical Link : Yes MTU : 1522
Single Fiber Mode : No Min Frame Length : 64 Bytes
IfIndex : 35749888 Hold time up : 0 seconds
Last State Change : 12/18/2012 15:58:29 Hold time down : 0 seconds
Last Cleared Time : N/A DDM Events : Enabled
Phys State Chng Cnt: 1
Configured Mode : access Encap Type : QinQ
Dot1Q Ethertype : 0x8100 QinQ Ethertype : 0x8100
PBB Ethertype : 0x88e7
Ing. Pool % Rate : 100 Egr. Pool % Rate : 100
Ing. Pool Policy : n/a
Egr. Pool Policy : n/a
Net. Egr. Queue Pol: default
Egr. Sched. Pol : n/a
Auto-negotiate : true MDI/MDX : unknown
Oper Phy-tx-clock : not-applicable
Accounting Policy : None Collect-stats : Disabled
Acct Plcy Eth Phys : None Collect Eth Phys : Disabled
Egress Rate : Default Ingress Rate : Default
Load-balance-algo : Default LACP Tunnel : Disabled
Down-when-looped : Disabled Keep-alive : 10
Loop Detected : False Retry : 120
Use Broadcast Addr : False
Sync. Status Msg. : Disabled Rx Quality Level : N/A
Tx DUS/DNU : Disabled Tx Quality Level : N/A
SSM Code Type : sdh ESMC Tunnel : Disabled
Down On Int. Error : Disabled
CRC Mon SD Thresh : Disabled CRC Mon Window : 10 seconds
CRC Mon SF Thresh : Disabled
Configured Address : d8:ef:01:01:00:03
Hardware Address : d8:ef:01:01:00:03
The operator also has the opportunity to decouple the efm-oam protocol from the port state and operational state. In cases where an operator wants to remove the protocol, monitor the protocol only, migrate, or make changes the ignore-efm-state can be configured in the port>ethernet>efm-oam context. When the ignore-efm-state command is configured on a port the protocol continues as normal. However, any failure in the protocol state machine (discovery, configuration, time-out, loops, and so on) does not impact the port on which the protocol is active and the optional ignore command is configured. There is only a protocol warning message if there are issues with the protocol. The default behavior when this optional command is not configured means the port state is affected by any efm-oam protocol fault or clear conditions. Adding and removing this optional ignore command immediately represents the Port State and Oper State based on the active configuration. For example, if the ignore-efm-state is configured on a port that is exhibiting a protocol error that protocol error does not affect the port state or operational state and there is no Reason Down code. If the ignore-efm-state is removed from a port with an existing efm-oam protocol error, the port transitions to Link UP, Oper Down with the reason code efmOamDown.