Network updates such as policy and routing changes occur frequently in Software Defined Networks (SDN). Updates should be performed consistently, preventing temporary disruptions, and should require as little overhead as possible. Scalability is increasingly becoming an essential requirement in SDN. In this paper we propose to use time-triggered network updates to achieve consistent updates. Our proposed solution requires lower overhead than existing update approaches, without compromising the consistency during the update. We demonstrate that accurate time enables far more scalable consistent updates in SDN than previously available. In addition, it provides the SDN programmer with fine-grained control over the tradeoff between consistency and scalability.
Time-of-day routing @cite_12 routes traffic to different destinations based on the time-of-day. Path calendaring @cite_45 can be used to configure network paths based on scheduled or foreseen traffic changes. The two latter examples are typically performed at a low rate and do not place demanding requirements on accuracy.
@cite_45 @cite_12
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Datacenter WAN traffic consists of high priority transfers that have to be carried as soon as they arrive alongside large transfers with pre-assigned deadlines on their completion (ranging from minutes to hours). The ability to offer guarantees to large transfers is crucial for business needs and impacts overall cost-of-business. State-of-the-art traffic engineering solutions only consider the current time epoch and hence cannot provide pre-facto promises for long-lived transfers. We present Tempus, an online traffic engineering scheme that exploits information on transfer size and deadlines to appropriately pack long-running transfers across network paths and time, thereby leaving enough capacity slack for future high-priority requests. Tempus builds on a tailored approximate solution to a mixed packing-covering linear program, which is parallelizable and scales well in both running time and memory usage. Consequently, Tempus is able to quickly and effectively update its solution when new transfers arrive or unexpected changes happen. These updates involve only small edits to existing transfers. Therefore, as experiments on traces from a large production WAN show, Tempus can offer and keep promises to long-lived transfers well in advance of their actual deadline; the promise on minimal transfer size is comparable with an offline optimal solution and outperforms state-of-the-art solutions by 2-3X. Description d'une methode generale pour implementer un systeme reparti ayant n'importe quel degre desire de tolerance de panne. La synchronisation par horloge fiable et une solution au probleme «Bizantine Generals» sont assumes