From: Erika Rice (erice@cs.washington.edu)
Date: Sun Oct 31 2004 - 11:51:08 PST
Review of "The Revised ARPANET Routing Metric" by Atul Khanna and John
Zinky:
In "The Revised ARPANET Routing Metric" Atul Khanna and John Zinky
describe the shortcomings of the then current ARPANET routing metric.
Based on these shortcomings, they designed and deployed a new routing
metric, HN-SPF (Hop-Normalized Shortest Path First) which solved some of
these problems with minimal change to the network.
This algorithm had several notable attributes. It used average values
instead of instantaneous values for quantities like queue length. The
realization that averages reduce the effects of transient network
fluctuations is an observations that is used extensively today and was a
great improvement over the instantaneous measurements used previously.
Also notable was the effectiveness of the algorithm. By just changing
the routing metric there was a 40% reduction in the round trip delay
packets experienced and a 13% increase in throughput. Although this can
be attributed to the improvements they made o the algorithm, part of
what made the changes so effective was the fact that the new algorithm
could be implemented throughout the whole network. The benefits that
are realizable with universal and efficient deployment can only be
imagined in today's Internet.
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