Event: NANOG 26, October 2002, Phoenix
Author(s): Arman Maghbouleh, Cariden
Recent research publications have noted the possibility that plain-old IGP metric manipulations may be as effective as the overlay-style traffic engineering made possible by ATM or MPLS. Adherents of either approach have pointed to specific topologies for which metric manipulation does extremely well or extremely poorly. Here, we present the results of a study comparing metric-based shortest-path routing with the theoretically optimal routing. We looked at six real networks under normal and single-circuit failures and found that, despite its limitations, metric-based routing was able to minimize maximum link utilizations about as well as the theoretical maximum. We present cases that illustrate the limitations of metric-based routing and speculate that these cases do not affect performance on existing networks because operators design networks with shortest-path routing limitations in mind.
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