The value of tmnxSubIPolRejectUnknownStrings specifies
if unknown subscriber strings are explicitly rejected by the system.
If the value of tmnxSubIPolRejectUnknownStrings is equal to 'false',
the system silently recovers using a known string that may be different
from the current string used by the subscriber.
If the value of tmnxSubIPolRejectUnknownStrings is equal to 'true',
unknown strings are refused with an error message, and the subscriber
strings are not modified.