Software Defined Networking - CompTIA A+ 220-1101 - 2.2

The advent of cloud
computing has changed

networking in many ways.

And if you're a
network administrator,

you know that in the
cloud, we don't usually

have physical routers, switches,
and other infrastructure

devices.

Instead, we need to take
these networking platforms we

use in the real
world and move them

into the virtualized
cloud-based world.

One way that we're
able to do this

is through the advent
of Software Defined

Networking or SDN.

With Software
Defined Networking,

we take those devices like
switches, routers, firewalls,

and other networking
infrastructure devices

and we change them to be
a software based platform

that we could use in the cloud.

This means that we might
take something like a switch

and separate all of the
functions of the switch

into individual pieces.

We can then take these
pieces and then create

software versions that we
can then run in the cloud.

There are commonly three
layers or three ways

to separate these
devices so that we

can create some consistency
across all of these networking

components.

The first layer would be
the infrastructure layer.

Sometimes we hear this
referred to as the data

plane of that device.

So it's common that
this data plane

would do the forwarding, the
trunking, the encrypting,

the Network Address Translation,
or anything else that needs

to occur at that packet level.

When our routers and switches
need to forward this traffic

in the data plane, they
need some type of reference

to know where this
traffic will be going.

Most of those references will be
in the control layer or control

plane of that device.

So if you have dynamic
routing protocols,

a forwarding table in a switch,
a Network Address Translation

table in a router,
all of those are

contained in the control plane.

And of course, you
or some other process

is in charge of
managing that device.

To be able to manage it,
we need to log in or access

the device via an API or
Application Programming

Interface.

And all of that
access is provided

at the application
layer or management

plane of that device.

So when you SSH into a
router, when you bring up

a graphical front
end of a firewall,

you're managing that device
from the management plane.

Let's see how this software
defined networking would

apply to a physical device.

And in this case, this physical
device appears to be a switch,

but this could be a
router or firewall

or any other
infrastructure device.

Let's start first with
that infrastructure layer

or the data plane.

If you're connecting to a
switch or you need traffic

forwarded between different
interfaces on a switch,

that all occurs in
that data plane.

This means we'll
take anything that

may be forwarding this
traffic on that device

and create a software
version of that

that we call the data plane.

These devices also need the
tables and forwarding structure

to be able to understand
where traffic is coming from

and where you'll be
forwarding it to,

and all that occurs in the
control layer or the control

plane.

And lastly, you'll be
managing this device probably

through a console
port or management

interface to the device, and
that section of the device

can be created as
the management plane.

Obviously with software
defined networking,

there is no physical
device, but you

can see where the data plane,
control plane, and management

plane are pulled from
our physical devices

to create this software based
networking infrastructure.

This now creates
modular layers that you

can extend between devices or
create new devices all based

on the Software
Defined Networking.

If we start, for
instance, at the bottom,

we know that
network traffic will

be traversing different
devices all at the data plane.

So communication between
those can occur solely

between those particular layers.

A device may need
to send or receive

dynamic routing protocols or
create tables for forwarding,

and all of those can
be done at the control

layer or the control plane of
Software Defined Networking.

And the layer that you're going
to manage these devices from

will be the management plane.

We usually access
the management plane

through Secure Shell, Simple
Network Management Protocol,

or an Application
Programming Interface.

You can see that
the Software Defined

Networking takes these very
standard categorizations

and extends them across
multiple networking devices

to create a very
modular architecture.

This allows you to have
a software based version

of these network devices that
we use on our physical networks

and be able to deploy them
and use them in a cloud-based

infrastructure.