Andreas Wundsam

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Software Defined Networks (SDN) give network designers freedom to refactor the network control plane. One core benefit of SDN is that it enables the network control logic to be designed and operated on a global network view, as though it were a centralized application, rather than a distributed system - logically centralized. Regardless of this abstraction,(More)
Debugging operational networks can be a daunting task, due to their size, distributed state, and the presence of black box components such as commercial routers and switches, which are poorly instrumentable and only coarsely configurable. The debugging tool set available to administrators is limited, and provides only aggregated statistics (SNMP), sampled(More)
The tussle between reliability and functionality of the Internet is firmly biased on the side of reliability. New enabling technologies fail to achieve traction across the majority of ISPs. We believe that the greatest challenge is not in finding solutions and improvements to the Internet's many problems, but in how to actually deploy those solutions and(More)
Software bugs are inevitable in software-defined networking control software, and troubleshooting is a tedious, time-consuming task. In this paper we discuss how to improve control software troubleshooting by presenting a technique for automatically identifying a minimal sequence of inputs responsible for triggering a given bug, without making assumptions(More)
In spite of the standardization of the OpenFlow API, it is very difficult to write an SDN controller application that is portable (i.e., guarantees correct packet processing over a wide range of switches) and achieves good performance (i.e., fully leverages switch capabilities). This is because the switch landscape is fundamentally diverse in performance,(More)
Today's networks are maintained by "masters of complexity": network admins who have accumulated the wisdom to troubleshoot complex problems, despite a limiting toolset. This position paper advocates a more structured troubleshooting approach that leverages architectural layering in Software-Defined Networks (SDNs). In all networks, high-level intent(More)
Software bugs are inevitable in software-defined networking (SDN) control planes, and troubleshooting is a tedious, time-consuming task. In this paper we discuss how one might improve SDN network troubleshooting by presenting a technique, retrospective causal inference, for automatically identifying a minimal sequence of inputs responsible for triggering a(More)
In this paper we leverage the structure of the SDN software stack to automate the process of troubleshooting networks. We present two techniques for programmatically localizing the root cause of network problems: crosslayer correspondence checking infers what problems exist in the network, and where in the control software the problem first developed; and(More)
Multimedia applications have recently been challenging existing mobile access networks and are raising the bar for next generation mobile networks (NGMN), both in terms of network traffic as well as in the expectations of end users. At the same time, the network and server landscape sees changes due to the advent of virtualization and split-architecture(More)