本篇学习笔记写于 Sun Nov 13 15:08:02 2016, 可能有认识不全面的地方.
参考资料为ONF的官方网站中: Software-Defined Networking (SDN) Definition, 之前也看了一些国内的网站, 然而基本上不知所云, 所以从ONF开始吧. link
What is SDN?
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The physical separation of the network control plane from the forwarding plane, and where a control plane controls several devices.
实现了网络的控制平面和转发平面的物理分离, 控制平面可以控制设备.
注意 : 这里并没有提到数据平面是个啥.
Software-Defined Networking (SDN) is an emerging architecture that is dynamic, manageable, cost-effective, and adaptable, making it ideal for the high-bandwidth, dynamic nature of today's applications. This architecture decouples the network control and forwarding functions enabling the network control to become directly programmable and the underlying infrastructure to be abstracted for applications and network services. The OpenFlow® protocol is a foundational element for building SDN solutions. The SDN architecture is:
软件定义网络（SDN）是一种新兴的架构，具有动态性，可管理性，成本效益和适应性，是当今应用的高带宽，动态特性的理想选择。 该架构将网络控制和转发功能解耦，使得网络控制变为可直接编程，并且为应用和网络服务提取底层基础设施。 OpenFlow协议是构建SDN解决方案的基本元素。 SDN架构是：
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Directly programmable: Network control is directly programmable because it is decoupled from forwarding functions.
网络控制器直接可编程, 因为它和转发功能分离.
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**Agile: **Abstracting control from forwarding lets administrators dynamically adjust network-wide traffic flow to meet changing needs.
灵活性: 抽象的控制方式可以使管理员动态控制网络流量, 以面对不断变化的需求.
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Centrally managed: Network intelligence is (logically) centralized in software-based SDN controllers that maintain a global view of the network, which appears to applications and policy engines as a single, logical switch.
集中控制: 这句话中文不太好翻译…看英文能看懂,
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Programmatically configured: SDN lets network managers configure, manage, secure, and optimize network resources very quickly via dynamic, automated SDN programs, which they can write themselves because the programs do not depend on proprietary software.
编程配置: SDN允许基于动态, 自动化的SDN程序, 快速地配置, 管理, 优化网络资源, 管理网络安全. 程序不依靠于专有软件
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**Open standards-based and vendor-neutral: **When implemented through open standards, SDN simplifies network design and operation because instructions are provided by SDN controllers instead of multiple, vendor-specific devices and protocols.
开放的, 供应商中立的: 当通过开放标准实施时，SDN简化了网络设计和操作，因为指令由SDN控制器提供，而不是由多个供应商特定的设备和协议提供。