ABSTRACT
1.单词学习
programmable:adj.可编程的。
trace:vt.追溯;查出;描摹;勾画出
active network: 主动网络
debunk:vt.揭穿......的真相，批判;嘲弄;
spur:v.加速;刺激;鼓舞;鞭策
Netword virtualization:网络虚拟化。网络虚拟化就是在一个物理网络上模拟出多个逻辑网络来，网络虚拟化的内容一般指虚拟专用网络 (VPN)，VPN 对网络连接的概念进行了抽象，允许远程用户访问组织的内部网络，就像物理上连接到该网络一样。
Open Flow:一种网络通信协议，属于数据链路层，能够控制网上交换器或路由器的转发平面（forwarding plane），借此改变网络数据包所走的网络路径
2.翻译
Software Defined Networking (SDN) is an exciting technology that enables innovation in how we design and manage networks. Although this technology seems to have appeared suddenly, SDN is part of a long history of efforts to make computer networks more programmable. In this paper, we trace the intellectual history of programmable networks, including active networks, early efforts to separate the control and data plane, and more recent work on OpenFlow and network operating systems. We highlight key concepts, as well as the technology pushes and application pulls that spurred each innovation. Along the way, we debunk common myths and misconceptions about the technologies and clarify the relationship between SDN and related technologies such as network virtualization.
软件定义网络（SDN）是一项令人兴奋的技术，它能使我们在设计和网络管理方面进行创新。虽然这个技术好像突然出现的样子，然而SDN是使计算机网络更加可编程的长期努力的一部分。在本文中，我们追溯可编程网络的智能发展历史，包括主动网络，早期致力于分离控制层和数据层，并且更多的致力于在OpenFlow和网络操作系统的工作。我们强调关键慨念，以及哪些加速了技术革新的技术推动和应用拉动。在这过程中，我们揭露了有关技术的常见神话和误解并且澄清了SND和像网络虚拟化等相关技术的关系。
1.Introduction
1.单词学习
middlebox:中间件;中间盒。中间盒是一种计算机网络设备,它转换、检查、筛选或以其他方式操纵通信量，以达到包转发以外的目的。
network adress translators(NAT):网络地址转换。
sever load balancers:服务器负载均衡。
intrusion detection systems:入侵监测系统。
dropping:丢弃，漏失。根据特定的规则丢弃分组。
forwarding:转发。把分组交付到下一站的方式。
flooding:泛滥。路由器接收到链接，状态更新信息时，不但更新自己的链接状态数据库，还需要将链接状态更新信息继续转播下去的过程
dynamic access control :动态访问控制。
energy-efficient network:节能网络
seamless virtual-machine migration:无缝虚拟机迁移。
user mobility:用户移动性。
distributed control software：分布式控制软件
Google’s wide-area trafficmanagement system：谷歌广域交通管理系统
Nicira’s Network Virtualization Platform：Nicira的网络虚拟化平台
这里把学术词专门剔出来，其他的因为每个人的英语程度不一样，就不专门再打出来了，就放上我的笔记图片吧。
Computer networks are complex and difficult to manage. These networks have many kinds of equipment, from routers and switches to middleboxes such as firewalls, network address translators, server load balancers, and intrusion detection systems. Routers and switches run complex, distributed control software that is typically closed and proprietary. The software implements network protocols that undergo years of standardization and interoperability testing. Network administrators typically configure individual network devices using configuration interfaces that vary across vendors—and even across different products from the same vendor. Although some network-management tools offer a central vantage point for configuring the network, these systems still operate at the level of individual protocols, mechanisms, and configuration interfaces. This mode of operation has slowed innovation, increased complexity, and inflated both the capital and operational costs of running a network
计算机网格是十分复杂的并且很难去管理。这些网络有各种各样的设备，从路由器和交换机到中间盒，例如防火墙，网络地址转换，服务器负载平衡和入侵检测系统。路由器和交换机运行复杂，分布式控制软件通常是密闭的和专有的。这个软件实现了经历多年标准化和互操作性测试的网络协议。网络管理员通常使用不同供应商的配置接口来配置单个网络设备,甚至在来自同一供应商的不同产品之间配置不同的配置接口。虽然一些网络管理工具对分配网络提供了一个中心优势，但这些系统仍然在一系列单独的协议，机制和配置接口上运行。这种运作模式降低了创新速度,增加了复杂性,并增加了运营网络的资本和运营成本。
Software Defined Networking (SDN) is changing the way we design and manage networks. SDN has two defining characteristics. First, an SDN separates the control plane (which decides how to handle the traffic) from the data plane (which forwards traffic according to decisions that the control planemakes). Second, an SDN consolidates the control plane, so that a single software control program controls multiple dataplane elements. The SDN control plane exercises direct control over the state in the network’s data-plane elements (i.e., routers, switches, and other middleboxes) via a well-defined Application Programming Interface (API). OpenFlow [51] is a prominent example of such an API. An OpenFlow switch has one or more tables of packet-handling rules. Each rule matches a subset of traffic and performs certain actions on the traffic that matches a rule; actions include dropping, forwarding, or flooding. Depending on the rules installed by a controller application, an OpenFlow switch can behave like a router, switch, firewall, network address translator, or something in between
软件定义网络正在改变我们设计和管理网络的方式，SDN有两个定义特征，第一，SDN从数据平面（根据控制平面所做的决定转发流量）中分离了控制平面（决定如何处理流量）。第二，SDN整合了控制平面，以至于一个单独的软件控制程序可以控制多个数据平面元素。SDN控制平面通过定义良好的应用程序编程接口(Api)直接控制网络数据平面元素(即路由器、交换机和其他中间盒）中的状态进行直接控制。OpenFlow是一个突出的API例子。OpenFlow交换机有一个或多个数据包处理规则表，每个规则匹配一个子集的流量，并对与规则匹配的流量执行某些操作。例如丢弃，转发，或者泛滥。依靠控制器应用程序安装的规则，OpenFlow交换机的行为可以类似于路由器、交换机、防火墙、网络地址转换器或介于两者之间的东西。
Over the past few years, SDN has gained significant traction in industry. Many commercial switches support the OpenFlow API. Initial vendors that supported OpenFlow included HP, NEC, and Pronto; this list has since expanded dramatically. Many different controller platforms have emerged [23, 28, 37, 46, 55, 63, 80]. Programmers have used these platforms to create many applications, such as dynamic access control [16, 53], server load balancing [39, 81], network virtualization [54, 67], energy-efficient networking [42], and seamless virtual-machine migration and user mobility [24]. Early commercial successes, such as Google’s wide-area trafficmanagement system [44] and Nicira’s Network Virtualization Platform [54], have garnered significant industry attention. Many of the world’s largest information-technology companies (e.g., cloud providers, carriers, equipment vendors, and financial-services firms) have joined SDN industry consortia like the Open Networking Foundation [57] and the Open Daylight initiative [56]
在过去几年里，SDN在工业方面取得了显著的吸引力。许多商业交换机支持OpenFlow API，最初支持OpenFlow的供应商提供了HP,NEandPronto，后来这个列表戏剧性地扩展了。许多不同的控制平台也出现了，程序员利用这些平台创造了许多应有软件，如动态访问控制、服务器负载平衡、网络虚拟化、节能网络、无缝虚拟机迁移和用户移动。早期的商业成功，如谷歌的广域交通管理系统和Nicira的网络虚拟化平台，已经引起了业界的极大关注。世界上最大的信息技术公司（例如云提供商、运营商、设备供应商和金融服务公司）加入了SDN行业联盟，如开放式网络基金会和Open Daylight方案。
Although the excitement about SDN has become more palpable during the past few years, many of the ideas underlying SDN have evolved over the past twenty years (or more!). In some ways, SDN revisits ideas from early telephony networks, which used a clear separation of control and data planes to simplify network management and the deployment of new services. Yet, open interfaces like OpenFlow enable more innovation in controller platforms and applications than was possible on closed networks designed for a narrow range of telephony services. In other ways, SDN resembles past research on active networking, which articulated a vision for programmable networks, albeit with an emphasis on programmable data planes. SDN also relates to previous work on separating the control and data planes in computer networks
尽管在过去几年，对SDN的兴奋变得更加明显了，但是许多SND的想法都是在过去20年中发展起来的。在某些方面，SDN重启了早期电话网络的想法，该网络使用控制和数据平面的明确分离来简化网络管理和新服务的部署。然而,像OpenFlow这样的开放接口使得在控制器平台和应用程序方面的创新超过了为范围狭窄的电话服务而设计的封闭网络上的创新。在其他方面，SDN类似于过去对主动网络的研究，它阐述了可编程网络的愿景，尽管重点是可编程数据平面，SDN还涉及到以前在计算机网络中分离控制平面和数据平面的工作。
In this article, we present an intellectual history of programmable networks culminating in present-day SDN. We capture the evolution of key ideas, the application “pulls” and technology “pushes” of the day, and lessons that can help guide the next set of SDN innovations. Along the way, we debunk myths and misconceptions about each of the technologies and clarify the relationship between SDN and related technologies, such as network virtualization. Our history begins twenty years ago, just as the Internet takes off, at a time when the Internet’s amazing success exacerbated the challenges of managing and evolving the network infrastructure. We focus on innovations in the networking community (whether by researchers, standards bodies, or companies), although we recognize that these innovations were in some cases catalyzed by progress in other areas, including distributed systems, operating systems, and programming languages. The efforts to create a programmable network infrastructure also clearly relate to the long thread of work on supporting programmable packet processing at high speeds
在这篇文章中，我们展示了可编程网络的知识历史，最终形成了今天的SDN.我们捕获了重要思想的演变，当今的应用“拉动”和技术“推动”，以及有助于指导下一组SDN技术创新。在此过程中，我们揭穿了关于每一项技术的神话和误解，并澄清了SDN与相关技术（如网络虚拟化）之间的关系。我们的历史始于20年前，就在互联网腾飞之际，互联网惊人的成功加剧了管理和发展网络基础设施的挑战。我们专注于网络社区的创新（无论是研究人员、标准机构还是公司），尽管我们认识到在某些情况下，这些创新是由其他领域的进步推动的，包括分布式系统、操作系统和编程语言，创建可编程网络基础设施的努力也显然与支持高速可编程分组处理的长线程有关
Before we begin our story, we caution the reader that any history is incomplete and more nuanced than a single storyline might suggest. In particular, much of the work that we describe in this article predates the usage of the term “SDN”, coined in an article [36] about the OpenFlow project at Stanford. The etymology of the term “SDN” is itself complex, and, although the term was initially used to describe Stanford’s OpenFlow project, the definition has since expanded to include a much wider array of technologies. (The term has even been sometimes co-opted by industry marketing departments to describe unrelated ideas that predated Stanford’s SDN project.) Thus, instead of attempting to attribute direct influence between projects, we instead highlight the evolution of and relationships between the ideas that represent the defining characteristics of SDN, regardless of whether or not they directly influenced specific subsequent research. Some of these early ideas may not have directly influenced later ones, but we believe that the connections between the concepts that we outline are noteworthy, and that these projects of the past may yet offer new lessons for SDN in the future.
在我们开始我们的故事之前，我们提醒读者，任何历史都是不完整的，比单一的故事情节可能暗示的更微妙。特别是，我们在本文中描述的大部分工作都是在使用术语“SDN”之前完成的，该术语是在一篇关于斯坦福OpenFlow项目的文章中创造的。术语“SDN”的词源本身就很复杂，尽管该术语最初用于描述斯坦福的OpenFlow项目，但此后该定义扩展到包括更广泛的一系列技术（这个词有时甚至被行业营销部门用来描述史丹福SDN项目之前不相关的想法）。因此，我们没有试图将项目之间的直接影响归因于项目之间，而是强调了想法的演变和想法之间的关系。它们代表了SDN的定义特征，不管它们是否直接影响到特定的后续研究，这些早期的一些想法可能没有直接影响到后来的想法，但我们认为，我们所概述的概念之间的联系是值得注意的，过去的这些项目可能会为未来的可持续发展网络提供新的教训。