Today's trend toward network
virtualization and software-defined networking enables flexible new distributed
systems where resources can be dynamically allocated and migrated to locations
where they are most useful. This paper proposes a competitive analysis approach
to design and reason about online algorithms that find a good tradeoff between
the benefits and costs of a migratable service. A competitive online algorithm
provides worst-case performance guarantees under any demand dynamics, and
without any information or statistical assumptions on the demand in the future.
This is attractive especially in scenarios where the demand is hard to predict
and can be subject to unexpected events. As a case study, we describe a service
(e.g., an SAP server or a gaming application) that uses network virtualization
to improve the quality of service (QoS) experienced by thin client applications
running on mobile devices. By decoupling the service from the underlying
resource infrastructure, it can be migrated closer to the current client
locations while taking into account migration costs. We identify the major cost
factors in such a system and formalize the wide-area service migration problem.
Our main contributions are a randomized and a deterministic online algorithm
that achieves a competitive ratio of O (login) in a simplified scenario, where
n is the size of the substrate network. This is almost optimal. We complement
our worst-case analysis with simulations in different specific scenarios and
also sketch a migration demonstrator.
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