Availability in Wide-Area Service Composition
Bhaskaran Raman, Randy H. Katz, SAHARA Project, EECS, U.C.Berkeley

Service composition across multiple providers is a powerful tool for
building new applications rapidly in next-generation networks.  Since
sessions could be composed across service instances deployed and
managed at different network locations by different providers, the
composition could stretch across the wide-area network.  This presents
challenges in terms of service availability since inter-domain
Internet path availability is known to be poor.  We have proposed and
evaluated an architecture for ROBUST and LOAD-BALANCED composition of
services.  Our architecture is based on an overlay network of service
clusters and uses alternate service instances and alternate network
paths to get around different kinds of failures.

A key feature of our solution is its ability to detect and recover
from failures QUICKLY.  Through a real implementation of a composed
text-to-speech application, and using experiments over the wide-area,
we have demonstrated that it is possible to mask long-lasting (tens of
seconds to minutes) network path failures.  We demonstrate end-to-end
session recovery times of 3-4 seconds for the text-to-speech
application.  This represents orders of magnitude better performance
than existing Internet path recovery [Labovitz'00].  In this poster,
we describe our wide-area experiments and the results.