The second possible link group available that can be used to reach a
neighbour which is the next hop in the path to the destination Node
for the specified Class of Service (COS). VNS traffic is routed
deterministically across the links in up to two link groups, when
available. If only one link group is available this attribute will be
left blank. The link groups selected are those associated with
minimum metric COS paths to the destination. If two link groups
are in use then the metric of the paths associated with each are
identical.
Link group instances are managed by the TransportResource
component. Further information about the links in the group can be
obtained from it.