The value of tmnxEthRingGuardTime specifies the guard timer, in
deciseconds, of a Ring-APS (R-APS) node.
The guard timer is used to prevent the Ethernet Ring node from acting
upon outdated R-APS messages and prevent the possibility of forming a
closed loop.
While the guard timer is running, any received R-APS Request/State and
Status information is blocked and not forwarded to the Priority Logic.
When the guard timer is not running, the R-APS Request/State and
Status information is forwarded unchanged.