Coursera SDN M1.1 SDN History: Central Control

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Structure

1.讨论SDN的时间线，从1980s至今。

2.认识到SDN背后的原则和idea。

3.识别SDN起源的架构主题。

NOTE

Four Chapter in SDN History:

(1)相关技术的演变。

(2)转控分离。

(3)对于特定的数据平面开发的控制信道(channels)。

(4)控制信道及数据平面的会聚收敛(convergence)。

1.Evolution of Supporting Technologys => Three Lessons

(1)集中式控制网络：AT&T网络，1980s。

彼时控制平面和数据平面耦合，有以下两大特点:

a.In-band Signaling

In telecommunications, in-band signaling is the sending of control information within the same band or channel used for voice or video.

共享同一条信道，负载大。

b.网络出错率高，不安全。

Thus:

AT&T => turn into DP and CP seperated, used in telephone network => provide various kinds of new services => spec: a & b & c

a.telephone network

--

b.signaling at NCP => back-end Database => customer info

--

c.benifits => deploy specific services on demand && rapid introduction of new services

=> spec - Benifits of the NCP and AT&T Network:

a.摒弃了In-band signaling从而降低开销：缩减环路(shorter circuits)的持续时间；在请求一个环路之前，能够决定其繁忙或空闲的状态。

b.对其新型服务的迅捷宣传.

=> results - Apps from composing the basic primitives that based on the NCP

a.收集N个摘要

b.发送消息给NCP

c.记录

d...

=> eg. Person Locator

a.User => register => NCP DB

b.NCP => route => location

总结：Benifits of Central Control

1.Network-wide vantage(优势) point

能够直接观察到整网行为

2.Independent evolution of infrastructure, data and services

服务和资源的分配取决于用户数据及网络负载。

(2)可编程性：积极网络，1990s。

(3)被称为杀手级应用的网络虚拟化：Switchlets，XEN，VINI，1990s。

2017/2/20