The hold MEP up on failure function allows MEP operation that is independent of SAP status. In order to report service-level agreement (SLA) metrics, transport providers run Y.1731 performance monitoring tests periodically. At preset times, transport providers initiate various tests to measure and record one or all required SLA components: jitter, delay, loss, and throughput. The ability to hold MEP up allows the MEP to be kept in operation even if the SAP is down or non-operational.
The hold MEP up on failure function applies only to Ethernet pseudowire services (Epipes) operating between SAPs or between SAPs and SDPs. The SAP connecting the provider equipment to the customer can be configured to hold the MEP in operation when the customer-facing SAP enters any failed state. Only one SAP per Epipe can be configured in this manner. Pseudowire status will indicate a failed SAP in the LDP status message, but as long as the pseudowire is in an operationally up state, it supports receiving frames from the network's far-end side. Counters are also incremented to accurately represent the number of received packets.
ETH-CFM PM measurements, ETH-CFM troubleshooting tools and connectivity, and ETH-CFM CCM processing and fault propagation are not impacted by this feature and continue to function normally.