Connectivity Fault Management Features

Fault Management can proactively monitor the network for faults and notify the administrator so that timely action can be taken to ensure the availability of the network.

Fault management includes:

• Fault detection
• Fault verification
• Fault isolation
• Fault notification
• Fault recovery

Continuity Check Protocol

ECFM uses the CC protocol to detect both connectivity failures and unintended connectivity between service instances. Each MEP can periodically transmit a multicast CCM announcing the identity of the MEP and its ME (Maintenance Entity), and track the CCMs received from the other MEPs. All connectivity faults indicate either misdirected CCMs or the differences between the CCMs received and the configured expectations of MEP. The state of the tracked CCMs is available to the operator for examination.

The following are the various error conditions that can be tracked through CCMs:

1. Loss of Continuity
2. Mismerge condition
3. Unexpected MEP
4. Unexpected MEG Level
5. Unexpected Period
6. Locally Detected Link Failure
7. Internal Hardware Failure
8. Internal Software Failure

LoopBack Protocol

ECFM uses the LB Protocol to support the fault verification functionality. Fault verification is an administrative action typically performed after fault detection. The operator initiates the unicast LBM (LoopBack Message) transmission from a specific MEP to an MEP/MIP or multicast LBM transmission to an ME. On reception of LBM, the MP (MEP/MIP) validates the received LBM and generates the unicast LBR (Loopback Reply), and transmits it to the originating MEP. The MEP records the information received in the LBR for examination by the operator.

Unicast LBM can be used for the following applications:

• To verify the bidirectional connectivity of an MEP with an MIP or a peer MEP.
• To perform a bidirectional in-service or out-of-service diagnostics test between a pair of peer MEPs. This includes verifying bandwidth throughput, detecting bit errors, and so on.

Multicast LBM can be used for the following application:

• To verify the bidirectional connectivity of an MEP with its entire ME.

LinkTrace Protocol

ECFM uses the LT Protocol to determine the Adjacent Relation Retrieval or for Fault Localization. The operator initiates the multicast LTM (Link Trace Message) transmission from a specific MEP to an MEP. On reception of LTM, the MP (MEP/MIP) generates the unicast LTR (Link Trace Reply), which is transmitted back to the originating MEP. The LTM is also forwarded to the next MP. The originating MEP accumulates the responses for examination by the operator.

Alarm Indication Signal

ECFM uses the AIS (Alarm Indication Signal) to suppress alarms at client-layer MEP(s), following the detection of a fault/Locked condition/AIS condition at the server-layer MEP. The operator can enable or disable the AIS functionality for an MEP, If AIS is enabled and a fault/Locked Condition/AIS Condition is detected at an MEP, AIS frames will be transmitted to the client-layer MEPs in the direction opposite to the peer MEP. On reception of the AIS frame, the client-layer MEP suppresses its fault alarms.

Locked Signal (LCK)

ECFM uses the LCK (Locked Signal) to communicate to its higher-level MEP(s) that the operator had deliberately interrupted the data traffic (Higher layer OAM PDUs and Data-frames), to perform some Out-Of-Service operations. The operator can enable or disable the Out-Of-Service condition on MEP. When enabled, LCK frames are transmitted to the client-layer MEP in the direction opposite to the peer MEP. On reception of LCK frames, the client-layer MEP suppresses its fault alarms, which may have been triggered by the administrative locking of data traffic at lower-level MEP.

Test Signal (TST)

ECFM uses the TST (Test Signal) to perform one-way In-Service or Out-Of-Service diagnostics tests or for verifying bandwidth throughput. Once the Test-Signal operation is initiated, TST frames are transmitted to the peer MEP. On reception of TST frames, the MEP checks the TST frames for bit errors and updates the relevant counters to be examined by the operator.

Maintenance Communication Channel (MCC)

ECFM uses the MCC (Maintenance Communication Channel) to support remote management between a pair of MEPs. On initiation, MCC frames are sent to the peer MEP. The received information in MCC frame is provided to the registered application.

Experimental OAM (EXP)

ECFM uses the EXP (Experimental OAM) to support Experimental OAM functionalities within an administrative domain. On initiation, the EXP frame is sent to the peer MEP, which in turn can respond with an EXR (Experimental OAM Reply) frame. The received information in EXP or EXR frame is provided to the registered application.

Vendor Specific OAM (VSP)

ECFM uses the VSP (Vendor Specific OAM) to support proprietary vendor-specific functionalities within an administrative domain. On initiation, the VSP frame is sent to the peer MEP, which in turn can respond with a VSR (Vendor Specific OAM Reply) frame. The received information in VSP or VSR frame is provided to the registered application.

Performance Monitoring

Performance monitoring is necessary to detect potential faults and to proactively notify an operator or peer network nodes. Such notification can further be used for protecting traffic and ensuring service availability and service level agreements. Frame Loss Measurement, Frame Delay Measurement, and Throughput Measurement together constitute performance monitoring

Frame Loss Measurement

ECFM uses the frame loss measurement function to get the value of the Frame Loss Ratio; it is expressed as the percentage of the number of service frames lost divided by the total number of service frames transmitted.

Frame Loss Ratio = (Number of service frames lost)/ (Total number of service frames transmitted)

Service frames include data frames and higher-layer OAM PDUs.

Loss Measurement is performed by sending frames with ETH-LM information to the peer MEP and by receiving frames with ETH-LM information from the peer MEP.

Frame Loss Measurement can be performed in the following ways:

• Dual-Ended ETH-LM, using CCM frame with ETH-LM information
• Single-Ended ETH-LM, using LMM (Loss Measurement Message) and LMR (Loss Measurement Reply) frame

Frame Delay Measurement

ECFM uses the frame delay measurement function to get the Frame Delay Value; it is expressed as the time elapsed since the start of transmission of the first bit of the frame by the source until the reception of the last bit by the destination.

These Measurements are performed by sending periodic frames with ETH-DM information to the peer MEP and by receiving frames with ETH-DM information from the peer MEP.

Frame Delay Measurement can be performed in the following ways:

• One-Way DM, using 1DM frame
• Two-Way DM, using DMM (Delay Measurement Message) and DMR (Delay Measurement Reply) frame

Frame Delay Variation Measurement

ECFM uses the frame delay variation measurement function to get IPDV (Inter-Packet Delay Variation) and PDV (Packet Delay Variation) values. These Measurements are determined by analyzing the Frame Delay values taken from Frame Delay Rolling Buffer.

Through Measurement

ECFM uses the throughput measurement function to get throughput value in units of bps (bits per second); it is expressed as the maximum rate in bps at which none of the offered frames are dropped by the device.

These measurements are performed by sending periodic ETH-LB or ETH-TST bursts to the peer MEP and receiving ETH-LB and ETH-TST frames from the peer MEP.

Throughput Measurement can be performed in the following ways:

• One-Way TH, using ETH-TST
• Two-Way TH, using ETH-LB