Bits set here represent defects and modes for switching all VCs within this Tunnel to another Tunnel that has no APS defects. Currently, only CEM defects are available. Separating and individually selecting CEM defects (buffer Danenberg et al Expires August 2001 32 Internet Draft MPLS CEM MIB February 2001 errors, header errors, etc.) is for future study. Also, for future study: determining a Tunnel's state of usefulness via other indications (such as OAM). If 'cemVcCriteria' is set, mplsCemTunnelExtApsViaCemVc is used to index the CEM VC for which defects are included. The purpose of this is in situations when CEM VCs can generate better defects than Tunnels (for example: buffer errors). Revertive and Hunt modes: 'revertive' is useful for non-primary Tunnels where you may want to switch back to a primary Tunnel that has no defects while the currently active also has no defects (see mplsCemTunnelExtApsRevertTimer). 'revertive' should NOT be used when standby Tunnels have no available defect indications. If 'revertive' is not set, then manual reversion is possible by simply setting the active Tunnel's admin status 'down', then 'up'. 'hunt' is useful when standby Tunnels offer no defect indications (see mplsCemTunnelExtApsHoldOffTimer). 'hunt' should not be used when standby Tunnels have available defect indications. Hunting assumes standby Tunnels are good, if not the down timers will determine it's bad, and hunting continues. 'hunt' and 'revertive' are mutually exclusive. Note: criteria defect bits here MUST align with mplsCemTunnelExtDefects so it can be used as a mask.