The value of tmnxPppQuality is a percentage used by LQM to
monitor the link quality. If the quality drops below this
percentage, the router shuts down the link. The percentages
are calculated for both the incoming and outgoing directions.
When LQM is enabled by setting tmnxPppQuality to a non-zero
value, Link Quality Reports (LQRs) are sent, in place of
keepalives, every keepalive period. All incoming keepalives
and/or LQRs are always responded to regardless of the setting
of tmnxPppQuality. A value of zero (0) implies no LQM quality
monitoring and is the only value supported.