This attribute indicates the state of the routing database exchange
with the peer node.
npDown: there are no active links (i.e. in the twoWayInside Hello
state) to the neighboring peer.
negotiating: the first step in creating an adjacency between the two
neighboring peers; this step determines which node is the master,
and what the initial DS sequence number will be.
exchanging: the node describes its topology database by sending
Database Summary packets to the neighboring peer.
loading: a full sequence of Database Summary packets has been
exchanged with the neighboring peer, and the required PTSEs are
requested and at least one has not yet been received.
full: All PTSEs known to be available have been received from the
neighboring peer. At this point the all ports leading to the neighbor
node will be flooded in PTSEs within the peer group.