This indicates the path diversification criteria -- node-based, SRLG-based, link-based, or a combination -- used to ensure this tunnel's path stays disjoint from another related path (typically its own backup). An admin selects SRLG-based specifically when protecting against shared-fiber-conduit risk is the priority, since node- or link-based disjointness alone doesn't guarantee the paths avoid a common physical duct. For example, a tunnel configured with SRLG-based disjoint type ensures its computed path avoids any shared-risk group with its backup, protecting against a single fiber cut taking down both.