  OSPF currently supports multi-area networking with two severe limitations,
due to the distance vector approach taken in the inter-area routing protocol:
(i) the multi-area topology is restricted to a two-level hierarchy, and (ii)
globally optimal routing may not be achieved. In this letter, we propose an
OSPF extension that overcomes these limitations by adopting a link state
inter-area routing protocol. The extension applies to both OSPFv2 (IPv4) and
OSPFv3 (IPv6), and is fully transparent to area-internal routers. Despite its
simplicity, this extension may have a large impact in the operation of the
current Internet.
