Tuning Dynamically Routed Internet Protocol Networks to Achieve Controlled and Predictable Failover During Link Instability

Internet protocol (IP) based networks have evolved greatly in the past decade from small manually-configured networks connecting small numbers of sites into global self-healing dynamic networks that connect, literally, everyone. With the advent of "network-centric" warfare, the network has become more important than ever to our warfighters on the ground, in the air, and at domestic and international locations. To support such large, complex, and rapidly changing networks, dynamic routing was developed, including the routing information protocol (RIP), interior gateway routing protocol (IGRP), border gateway protocol (BGP), open shortest path first, and finally, enhanced IGRP (EIGRP). This paper looks at an approach for tuning dynamic routing systems using link metrics and focusing on the EIGRP dynamic routing protocol in order to achieve consistent, reliable, and predictable failover of dynamically routed links in complex networks. It examines: architectural issues for designing enterprise network backbones with redundant links; operational routing issues associated with configuring "hot spare" routers and contingency backbone sites; and finally a metrics system for tuning the routing system where multiply redundant links (redundant groups of redundant links) are used