This reports the maintenance domain (MD) level, an integer from 0 to 7 defined by 802.1ag/Y.1731, associated with this CFM service, which establishes the hierarchical scope (e.g. customer, provider, operator level) at which this service's MEPs exchange CCM messages. An admin needs this because CFM frames at one MD level are transparent to (ignored by) devices operating at a different level, so mismatched MD levels between two ends of a service are a classic cause of CFM sessions that never come up even though the physical path is fine. For example, a service configured at MD level 5 (provider level) on one switch but level 6 (operator level) on the peer would never establish CCM continuity, even though both switches are otherwise correctly configured for CFM.