2.3 OpenFlow and Network OSes

单词学习

翻译

In the mid-2000s, researchers and funding agencies gained interest in the idea of network experimentation at scale, encouraged by the success of experimental infrastructures (e.g., PlanetLab [6] and Emulab [83]), and the availability of separate government funding for large-scale “instrumentation” previously reserved for other disciplines to build expensive, shared infrastructure such as colliders and telescopes [52]. An outgrowth of this enthusiasm was the creation of the Global Environment for Networking Innovations (GENI) [33] with an NSF-funded GENI Project Office and the EU FIRE program [32]. Critics of these infrastructure-focused efforts pointed out that this large investment in infrastructure was not matched by well-conceived ideas to use it. In the midst of this, a group of researchers at Stanford created the Clean Slate Program and focused on experimentation at a more local and tractable scale: campus networks

2000年代中期，受尝试根本设施告成的鼓励，研究人员和扶助机构对大规模网络尝试的想法孕育产生了兴趣，当局为大型“仪器”单独供给资金，这些大型“仪器”以前是留给其他学科建造昂贵的共享根本设施，如对撞机和望远镜。这种热情的一个功效是创建了全球网络创新环境（GENI），由NSF扶助的GENI项目办公室和欧盟消防打算。也有攻讦者指出，对根本设施的这一大笔投资并没有与使用它的精心构思的想法相匹配。在此过程中，斯坦福大学的一组研究人员创建了一个全新的项目，并将重点放在更本地化、更易措置惩罚惩罚的规模上——校园网。

Before the emergence of OpenFlow, the ideas underlying SDN faced a tension between the vision of fully programmable networks and pragmatism that would enable realworld deployment. OpenFlow struck a balance between these two goals by enabling more functions than earlier route controllers and building on existing switch hardware, through the increasing use of merchant-silicon chipsets in commodity switches. Although relying on existing switch hardware did somewhat limit flexibility, OpenFlow was almost immediately deployable, allowing the SDN movement to be both pragmatic and bold. The creation of the OpenFlow API [51] was followed quickly by the design of controller platforms like NOX [37] that enabled the creation of many new control applications

在OpenFlow呈现之前，SDN的根基思想面临着完全可编程网络和实用主义之间的紧张关系，后者将使RealWorld部署成为可能。OpenFlow在这两个方针之间取得了平衡，它启用了比早期路由控制器更多的成果，并通过在商品交换机中越来越多地使用商用硅芯片组来构建现有的交换机硬件。尽管依赖现有的交换机硬件在必然水平上限制了灵活性，但OpenFlow几乎可以当即部署，这使得SDN的移动既实用又斗胆，OpenFlow API的创建之后，紧接着是NOX这样的控制器平台的设计，它撑持创建许多新的控制应用措施。

An OpenFlow switch has a table of packet-handling rules, where each rule has a pattern (that matches on bits in the packet header), a list of actions (e.g., drop, flood, forward out a particular interface, modify a header field, or send the packet to the controller), a set of counters (to track the number ofbytes and packets), and a priority (to disambiguate between rules with overlapping patterns). Upon receiving a packet, an OpenFlow switch identifies the highest-priority matching rule, performs the associated actions, and increments the counters

OpenFlow交换机有一个数据包措置惩罚惩罚法则表，此中每个法则都有一个模式（与数据包头中的位匹配）、一个操纵列表（例如，抛弃、溢出、转发特定接口、改削头字段或将数据包发送到控制器）、一组计数器（用于跟踪字节和数据包的数量）和优先级（消除具有重叠模式的法则之间的歧义）。在接收到数据包时，OpenFlow交换机识别最高优先级匹配法则，执行相关操纵，并递增计数器。

Technology push and use pull. Perhaps the defining feature of OpenFlow is its adoption in industry, especially as compared with its intellectual predecessors. This success can be attributed to a perfect storm of conditions between equipment vendors, chipset designers, network operators, and networking researchers. Before OpenFlow’s genesis, switch chipset vendors like Broadcom had already begun to open their APIs to allow programmers to control certain forwarding behaviors. The decision to open the chipset provided the necessary impetus to an industry that was already clamoring for more control over network devices. The availability of these chipsets also enabled a much wider range of companies to build switches, without incurring the substantial cost of designing and fabricating their own data-plane hardware.