Reason why CM is considered to be impaired. Reason codes with lower integer values take precedence over reason codes with higher values if multiple reasons apply to the same CM. The unknownMdDsSgId reason is used whenever the MD-DS-SG-ID reported in the B-INIT-RNG-REQ message is 0 and the CMTS cannot otherwise determine which downstream service group the CM is contained within. The unknownMdUsSgId reason is used whenever the MD-DS-SG-ID is known for the CM but the MD-US-SG cannot be determined by the topology resolution process. This reason may indicate an undiagnosed connectivity problem in the cable network whereby the true connectivity does not match the provisioned connectivity. It may also indicate one or more corrupted upstream channels. The badRcs reason indicates that the CM was unable to tune to and receive a downstream channel that is assigned to the CM in the RCC. This may indicate an undiagnosed connectivity problem or a CM receiver problem. The badTcs reason indicates that CM was unable to successfully range on one or more upstream channels that were assigned to the CM in the TCC. This reason may indicate an undiagnosed connectivity problem in the cable network whereby the true connectivity does not match the provisioned connectivity. It may also indicate one or more corrupted upstream channels. This reason may also indicate that the supervision for one or more upstream channels cannot be found within the RCS. The qamFecLockFailure reason indicates that the CM has reported that one or more previously known good downstream channels has lost FEC lock. This reason supercedes unknownMdDsSgId. The t4Timeout indicates that the CM has reported that it has experienced a timeout event for DOCSIS timer T4 (Periodic Ranging opportunities interval). The t3Timeout reason indicates that the CM has reported that it has exceeded the maximum number of consecutive timeouts of timer T3 (ranging response timer). The usStationMaintFailure indicates that C4 has detected that CM is experiencing periodic ranging failure.