Configuration changes are a common source of instability in networks, leading to broken connectivity, forwarding loops, and access control violations. Even when the initial and final states of the network are correct, the update process often steps through intermediate states with incorrect behaviors. These problems have been recognized in the context of specific protocols, leading to a number of point solutions. However, a piecemeal attack on this fundamental problem, while pragmatic in the short term, is unlikely to lead to significant long-term progress. Software-Defined Networking (SDN) provides an exciting opportunity to do better. Because SDN is a clean-slate platform, we can build general, reusable abstractions for network updates that come with strong semantic guarantees. We believe SDN desperately needs such abstractions to make programs simpler to design, more reliable, and easier to validate using automated tools. Moreover, we believe these abstractions should be provided by a runtime system, shielding the programmer from these concerns. We propose two simple, canonical, and effective update abstractions, and present implementation mechanisms. We also show how to integrate them with a network programming language, and discuss potential applications to program verification.

Abstract—OS virtualization and cloud computing have radically changed the way Internet services are deployed: enterprises share third-party datacenters, deploying existing applications with minimal changes. Recent measurements reveal a lack of traffic isolation capabilities within the datacenter with network performance exhibiting high variability. We advocate addressing this problem by allowing applications to express their own forwarding logic using OpenFlow to achieve application specific optimal performance. We present an OpenFlow implementation within the Mirage application synthesis framework, in the form of library implementations of a modular controller and an extensible OpenFlow-enabled switch, able to expose the underlying network infrastructure to cloud applications. By linking into the application, this provides a safe yet highly extensible framework for programming network control that, although unoptimised, still provides reasonable performance when compared with existing controllers. I.

For the past 30 years, networks have been built the same way: out of special-purpose devices running distributed algorithms that provide functionality such as topology discovery, routing, traffic monitoring, and access control. Recent

Abstract—Software Defined Networking (SDN in short) is reshaping the future of computer networks. By decoupling control and data planes, SDN technologies allow a more flexible management of network infrastructures, whose resources may be operated by means of a well defined programming interface. Several approaches have been recently proposed to implement the SDN concept. OpenFlow is maybe the most prominent SDN component, having been supported by several device vendors. This paper discusses a practical experience in designing an OpenFlow controller for a Mobile Cloud Management system. We present the programming model and the designed abstraction and discuss the lesson learned. Index Terms—Software-Defined Networking, OpenFlow controller, scalability, programming model I.