Abstract

Abstract
In the currently dominant cloud computing paradigm, applications are being served in data
centers (DCs), which are connected to high capacity optical networks. For bandwidth and
consequently cost efficiency reasons, in both DC and optical network domains, virtualization
of the physical hardware is exploited. In a DC, it means that multiple so-called virtual
machines (VMs) are being hosted on the same physical server. Similarly, the network is
partitioned into separate virtual networks, thus providing isolation between distinct virtual
network operators (VNOs). Thus, the problem of virtual network mapping arises: how to
decide which physical resources to allocate for a particular virtual network? In this thesis,
we study that problem in the context of cloud computing with multiple DC sites. This
introduces additional flexibility, due to the anycast routing principle: we have the freedom
to decide at what particular DC location to serve a particular application. We can exploit
this choice to minimize the required resources when solving the virtual network mapping
problem.
This thesis solves a resilient virtual network mapping problem that optimally decides
on the mapping of both network and data center resources, considering time-varying traffic
conditions and protecting against possible failures of both network and DC resources. We
consider the so-called VNO resilience scheme: rerouting under failure conditions is provided
in the virtual network layer. To minimize physical resource capacity requirements, we allow
reuse of both network and DC resources: we can reuse the same resources for the rerouting
under failure scenarios that are assumed not to occur simultaneously. Since we also protect
against DC failures, we allocate backup DC resources, and account for synchronization
between primary and backup DCs. To deal with the time variations in the volume and geographical
pattern of the application traffic, we investigate the potential benefits (in terms
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of overall bandwidth requirements) of reconfiguring the virtual network mapping from one
time period to the next. We provide models with good scalability, and investigate different
scenarios to check whether it is worth to change routing for service requirement between time
periods. The results come up with our experiments show that the benefits for rerouting is
very limited.
Keywords: Cloud Computing, Optical Networks, Virtualization, Anycast, VNO resilience