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June 16, 2016
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Network management is critical to provide fast, reliable and secure network services.
Software-defined networking (SDN) is a new network architecture to simplify network
management by integrating network control to a centralized control platform.
Network operators run various applications on the control platform to perform different
management tasks, like routing, monitoring, load balancing and firewall. These applications
have complex interactions with each other, making it difficult to deploy and reason
about their behaviors. The frequent network events, such as traffic shifts, cyber attacks,
and device failures, further exacerbates the problem. Each application needs to reconfigure
the network, in order to react to the events. It is challenging to correctly and efficiently
combine configuration changes from multiple applications, distribute these changes to a
distributed collection of network devices, and coordinate changes across network devices
in different layers.
In this thesis, we present a new control architecture that can efficiently handle network
events for multiple applications and across the network and optical layers. We identify and
study the following three key components of the architecture.
(i) CoVisor: A network hypervisor that can compose multiple applications and can effi-
ciently merge configuration changes from these applications in the face of network events.
To protect the network from malicious and buggy applications, CoVisor also provides
topology virtualization and fine-grained access control to constrain what each application
can see and do.
(ii) Dionysus: A network update scheduler that can quickly and consistently distribute
configuration changes to multiple switches. Dionysus uses a dependency graph to capture
the dependencies between update operations, and dynamically schedules the operations
based on runtime conditions. The approach both eliminates undesirable transient behaviors
like loops, blackholes and congestion, and reduces the update time.
(iii) Owan: A traffic management system that can jointly control the optical and network
layers. Owan optimizes optical circuit setup, routing and rate allocation together,
and dynamically adapts them to workload changes. The joint management significantly
improves data transfers over the wide area network.
We have built software controllers and hardware testbeds, and evaluated them with prototype
experiments and large-scale simulations using network topologies and traffic traces
from production networks.

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