Advantages of Software Defined Networking are unquestionable and are widely described in numerous scientific papers, business white papers and press articles. However, to achieve full maturity, crucial impediments to this concept and its shortcomings must be overcame. One of the most important issues regards significant setup latency of a new flow. To address this issue we propose PARD: a hybrid proactive and reactive method to manage flow table entries. Additional advantages of the proposed solution are, among the others, its ability to preserve all capabilities of Software Defined Networking, utilization of multiple flow tables, a possibility to employ fine-grained traffic engineering and, finally, compatibility with existing protocol and hardware design. It is shown that the proposed solution is able to significantly reduce latency of first packets of a new flow, which directly impacts packet loss and perceived throughput. Thus, our solution is expected to enable a wide deployment of Software Defined Networking concept without any need for protocol changes or, what is extremely important, hardware modifications.

中文翻译：

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PARD：在 SDN 中消除流设置延迟的混合主动和反应方法

软件定义网络的优势是毋庸置疑的，并且在众多科学论文、商业白皮书和新闻文章中得到了广泛的描述。然而，要实现完全成熟，必须克服这一概念的关键障碍及其缺点。最重要的问题之一是新流的显着设置延迟。为了解决这个问题，我们提出了 PARD：一种管理流表条目的混合主动和被动方法。所提议的解决方案的其他优点包括保留软件定义网络的所有功能、使用多个流表、采用细粒度流量工程的可能性以及与现有协议和硬件设计的兼容性。结果表明，所提出的解决方案能够显着减少新流的第一个数据包的延迟，这直接影响数据包丢失和感知吞吐量。因此，我们的解决方案有望实现软件定义网络概念的广泛部署，而无需更改协议或非常重要的硬件修改。