This variable indicates if the PTSE of this node
is currently contained in the PNNI PTSE database. The
nodal information in the persistent topology database
is derived from the PTSEs in the PNNI PTSE database.
The entries in the PNNI PTSE database times out if no
new PTSE is received from a node after a certain
time. If that happens, this object is set to 'false'.
This object would allow the NMS to determine whether
this node currently has connectivity with the rest of
the network.