Rama：实现软件定义网络中的控制器容错
Rama: Controller Fault Tolerance in Software-Defined Networking Made Practical
摘要：
在软件定义网络（SDN）中，网络应用使用由控制器提供的逻辑集中式网络视图来远程编排网络交换机。为了避免控制器成为单点故障，采用传统的容错技术来保证可用性，这是生产环境中的基本要求。不幸的是，这些技术无法确保在控制器故障下的正确网络行为。这些技术的问题在于它们只处理了问题的一部分：保证应用程序和控制器状态在副本之间保持一致。然而，在SDN中，交换机保持也必须一致地处理的硬状态。因此，容错SDN必须将交换机状态纳入问题中。最近提出的容错控制器平台Ravana通过扩展容错SDN控制来解决这个问题，该容错SDN控制具有保证控制消息在控制器和交换机处被事务性地且精确地处理一次的机制。即使在控制器和开关崩溃的情况下也能提供这些保证。这种解决方案的优雅是有代价的。Ravana要求修改交换机，并对OpenFlow进行扩展，以增加迄今为止未预见到的协议。面对这一挑战，我们提出了Rama，这是一个容错SDN控制器平台，它提供了与Ravana相同的强大保证，而无需修改交换机或OpenFlow协议。我们的原型实现的实验表明，额外的开销是适度的，使Rama的第一个容错SDN解决方案，可以立即部署。
英文摘要：
In Software-Defined Networking (SDN), network applications use the logically centralized network view provided by the controller to remotely orchestrate the network switches. To avoid the controller being a single point of failure, traditional fault-tolerance techniques are employed to guarantee availability, a fundamental requirement in production environments. Unfortunately, these techniques fall short of ensuring correct network behaviour under controller failures. The problem of these techniques is that they deal with only part of the problem: guaranteeing that application and controller state remains consistent between replicas. However, in an SDN the switches maintain hard state that must also be handled consistently. Fault-tolerant SDN must therefore include switch state into the problem. A recently proposed fault-tolerant controller platform, Ravana, solves this problem by extending fault-tolerant SDN control with mechanisms that guarantee control messages to be processed transactionally and exactly once, at both the controllers and the switches. These guarantees are given even in the face of controller and switch crashes. The elegance of this solution comes at a cost. Ravana requires switches to be modified and OpenFlow to be extended with hitherto unforeseen additions to the protocol. In face of this challenge we propose Rama, a fault-tolerant SDN controller platform that offers the same strong guarantees as Ravana without requiring modifications to switches or to the OpenFlow protocol. Experiments with our prototype implementation show the additional overhead to be modest, making Rama the first fault-tolerant SDN solution that can be immediately deployable.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
