USITS 2001 Abstract
End-to-End WAN Service Availability
Bharat Chandra, Mike Dahlin, Lei Gao, and Amol Nayate, University of Texas at Austin
This paper seeks to understand how network failures affect the availability
of service delivery across wide area networks and to evaluate classes of
techniques for improving end-to-end service availability. Using several
large-scale connectivity traces, we develop a model of failures that includes
key parameters such as failure location and failure duration. We then use
trace-based simulation to evaluate several classes of techniques for coping
with network failures. We find that caching alone is seldom effective at
insulating services from failures but that the combination of mobile extension
code and prefetching can improve failure rates by as much as an order of
magnitude for classes of service whose semantics support disconnected operation.
We find that routing-based techniques may provide significant improvements,
but that the improvements of many individual techniques are limited because
they do not address all significant categories of network failures. By
combining the techniques we examine, some systems may be able to improve
availability by as much as one or two orders of magnitude.
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