Nimrod
Nimrod was a proposed routing architecture for the Internet; intended to provide a very powerful routing system, one that would also scale indefinitely as the Internet grew (like DNS does).
It covers a lot more than just path selection. That's because the architecture embodied in IPv4 was missing lots of things which one would need to do the internet layer 'right' in a global-scale Internet (e.g. variable length 'addresses' - for which Nimrod was forced to invent the term 'locator' because many people in the IETF couldn't wrap their minds around 'addresses' which weren't in every packet header). And separation of location and identity; and the introduction of traffic aggregates as first-class objects at the internet layer. Etc, etc, etc.
Nimrod's main focus was really on i) providing a path-selection system which allowed things like letting users have more input to selecting the path their traffic took (just as when one gets into a car, one gets to pick the path one is going to use), and ii) controlling the overhead of the routing.
In terms of mechanism, it distributed maps (like the so-called new ARPANET routing protocol), not routing tables, as the fundamental data. That allowed network elements to be tagged with 'attributes', which the path-selection algorithm could take into account; that allowed a much richer semantics in describing paths. It also had a datagram mode, where single packets could be sent without needing any set-up.
