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- In the last decade,

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there have been so many changes

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and shifts in networking technologies.

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Some of the changes

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are due to the demand
of modern applications,

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right,

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especially applications
that are now hosted

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in many different environments,

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not only in a data center

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but in many different cloud environments.

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So this complexity introduces risks

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including network configuration errors

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and also network security challenges,

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right?

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Subsequently,

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networking functions like routing

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and optimization and
security also have changed.

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And the next generation of
hardware and software components

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in the enterprise need to
support this rapid introduction

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and evolution of new
technologies and solutions.

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So this network infrastructure,

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you know

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must keep pace with the
business environment

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and support modern capabilities

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that will actually, at the end of the day,

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help drive simplification
within the network.

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So these elements have
helped with the creation

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of a concept called
Software Defined Networking

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and SDN,

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you know,

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or Software Defined Networking

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was actually originally
created to decouple control

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from the forwarding functions
in the networking equipment.

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And this is actually done

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to use software,

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basically,

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to centrally manage and program

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this concept of programmability,

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right,

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and you know

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manage and program the hardware

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and virtual networking appliances

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to actually perform,

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you know,

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network forwarding

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and routing and network functions.

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Now,

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traditional routing and switching,

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you know

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have actually addressed
three different planes.

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You actually have the Management Plane,

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where you have configuration
and monitoring,

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typically done via,

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you know,

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a CLI or GUI and each vendor

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actually has their own proprietary way

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to configure the devices.

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And then you have Control Plane

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and that's actually involves
layer 2 and layer 3 protocols,

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you know

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and things like routing
protocols, like OSPF, RIP, BGP

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and et cetera.

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Now you also have the Data Plane

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and that's where,

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or you know,

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how data is actually forwarded
inside of the hardware

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from interface to interface

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and from device to device.

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So in SDN,

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we introduce the notion of
a centralized controller

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and that SDN controller,

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has actually a global view of the network

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and it uses common management protocols

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to configure the network
infrastructure devices.

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Right?

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It also can use things like,

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you know

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restful APIs

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to provide configuration

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and streaming services,

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to obtain telemetry

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from the network devices as well.

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Now the SDN controller

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can also calculate

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the reach-ability information

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from many systems in the network

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and pushes a lot of set
of flows inside switches

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and networking gear.

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Now there are many different
examples of open source

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and commercial implementations
of SDN controllers.

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Now an example is the Open vSwitch OVS

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and it's a project using a
database called the OVS database

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or OVS DB for the management of,

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you know

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the networking devices or
network virtual devices as well.

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Now the other one is Open Flow...

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the Open Flow Protocol.

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And you're gonna be learning a lot more

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about that later in the course,

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but I want to

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also give you somewhat of a preview

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of yet another example

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but in this case it's
actually a commercial

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and Cisco's,

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you know

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implementation of an SDN controller,

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which is

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the Cisco Application Policy
Infrastructure Controller

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or Cisco APIC,

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right?

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And APIC is the main
architectural component

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or you can call it the brains

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of the Cisco Application
Centric Infrastructure

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or ACI solution.

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And those are actually great examples.

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And you're gonna be learning
a lot more about them,

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later in the course.

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You're also gonna be learning

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about the differences between Northbound

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and Southbound APIs

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in the SDN architecture,

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and then you know

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also about other implementations

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like the Cisco DNA and
the Cisco DNA center.