Dynamic Control of Software-Defined Networks

Abstract

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 efficiently 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.