The object tmnxOamAncpHistoryAccNodeCode indicates, if different
from 0, the return code received from the ANCP access node.
The value of this field corresponds to the errorcodes defined in the
draft-wadhwa-gsmp-l2control-configuration-01:
- 0x500 Specified access line does not exist
- 0x501 Loopback test timed out
- 0x502 Reserved
- 0x503 DSL line status showtime
- 0x504 DSL line status idle
- 0x505 DSL line status silent
- 0x506 DSL line status training
- 0x507 DSL line integrity error
- 0x508 DSLAM resource not available
- 0x509 Invalid test parameter