This paper considers the use of compound cost functions in routing calculations. Using an abstracted version of Cisco’s EIGRP as its basic model, it develops the theoretical principals of optimal end-to-end interior routing then details the limitations of conventional and current implementation. The requirements of an improved system are discussed and proposals for an enhanced Ant Colony Optimisation - DUAL protocol given. A comparative example is used to illustrate the points made and further work needed and other open questions are considered in conclusion. The paper has two purposes. In the main, it provides an analysis of current routing protocols and a model for future ones. In part, however, it is also intended to promote debate into many aspects of Internet routing and its ‘optimality’ in advance of long-term development of the new protocol
