Set by the operator to indicate the outer tunnel types, if
exists. mplsTe is used if the outer tunnel was set-up by
MPLS-TE, and mplsNonTe is used the outer tunnel was set up
by LDP or manually. Combination of mplsTe and mplsNonTe
may exist in case of outer tunnel protection.
vcOnly is used if there is no outer tunnel label. vcOnly
cannot be combined with mplsNonTe or mplsTe.