| 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 (OSPF), and finally, Enhanced IGRP (EIGRP).
As networks have been extended from the strategic to the tactical levels, the speed at which the networks change has risen dramatically at the same time that the reliability of the links upon which they rely has dropped. Unfortunately, the networks that we rely upon have sometimes evolved faster than the dynamic routing technologies supporting them, resulting in network instability and configuration challenges as system operators scramble to keep things running in rapidly changing and unreliable environments. Dynamic routing is the obvious answer to this challenge, but several factors hamper its implementation in real-world, operational environments. One of these factors is the challenge of achieving consistent, reliable, predictable failover of routing from primary to secondary and tertiary paths when links become unavailable.
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.
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| Mr. Williams has been using digital security systems since 1994, and has worked on US Army electronic networks and information, the Defense Message System, and in support of the Joint Staff, National Security Agency, and Department of State. Mr. Williams is currently employed by Science Applications International Corporation (SAIC), with prior experience at Electronic Data Systems (EDS) and Booz Allen Hamilton. Mr. Williams spent five years as a Ranger- and jumpmaster-qualified paratrooper in the US Army, performing command and staff duties within the 82nd Airborne Division and XVIIIth Airborne Corps. Mr. Williams has a Bachelor’s of Science degree in Computer Science Engineering from Princeton University. |