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 SoftwareDefined Networks (SDNs). In all networks, high-level intent (policy) must correctly map to low-level forwarding behavior (hardware configuration). In SDNs, intent is explicitly expressed, forwarding semantics are explicitly defined, and each architectural layer fully specifies the behavior of the network. Building on these observations, we show how recently-developed troubleshooting tools fit into a coherent workflow that detects mistranslations between layers to precisely localize sources of errant control logic. Our goals are to explain the overall picture, show how the pieces fit together to enable a systematic workflow, and highlight the questions that remain. Once this workflow is realized, network admins can formally verify that their network is operating correctly, automatically troubleshoot bugs, and systematically track down their root cause -freeing admins to fix problems, rather than diagnose their symptoms.
Software bugs are inevitable in software-defined networking control software, and troubleshooting is a tedious, time-consuming task. In this thesis 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 about the language or instrumentation of the software under test. We apply our technique to five open source SDN control platforms-Floodlight, NOX, POX, Pyretic, ONOS-and illustrate how the minimal causal sequences our system found aided the troubleshooting process.
AcknowledgmentsMany thanks to the STS team for making this thesis possible:
Software bugs are inevitable in software-defined networking control software, and troubleshooting is a tedious, time-consuming task. In this thesis 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 about the language or instrumentation of the software under test. We apply our technique to five open source SDN control platforms-Floodlight, NOX, POX, Pyretic, ONOS-and illustrate how the minimal causal sequences our system found aided the troubleshooting process.
AcknowledgmentsMany thanks to the STS team for making this thesis possible:
SUMMARYThe data rates provisioned by broadband Internet access connections continue to fall short of the requirements posed by emerging applications. However, the potential of statistical multiplexing of the last mile broadband connections remains unexploited even as the average utilisation of these connections remains low. Despite recent work in this area, two key questions remain unanswered: (a) what is the attainable benefit of broadband access sharing? and (b) how much of this benefit is realisable given real-world constraints? In this work we quantify the attainable benefit of a multihomed broadband access environment by proposing and evaluating several flow-based access sharing policies using a custom flow-based simulator. We then analyse how much of the performance benefit is lost due to real-world constraints by migrating from simulations to a test-lab environment employing a wireless network. Our results show that in today's broadband Internet access scenarios, a significant reduction in download times (up to a factor of 3) is achievable.
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