Uniquely identifies a set of tunnels
between a pair of ingress and egress LSRs.
Managers should obtain new values for row
creation in this table by reading mplsTunnelIndexNext.
When the MPLS signalling protocol is rsvp(2),this value
should be equal to the value signalled in the tunnel ID
of the session object. When the MPLS signalling protocol
is crldp(3) this value should be equal to the value
signalled in the LSP ID. Reference to MPLS-TE-STD-MIB.