WEBVTT

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>> Now, as we mentioned earlier,

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when we have a network,

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we have a group of
interconnected devices.

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How do we connect those devices?

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We connect them through
media and through

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specific devices designed
to connect computers.

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Hubs are what we used to use

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very commonly back in the day,

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simply for the fact
that they were cheap.

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But hubs introduced problems and

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some security vulnerabilities
into the network,

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so we moved from
hubs to switches.

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Switches give us greater
control of traffic,

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and switches, in a lot of ways,

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act like a police officer
of a busy intersection;

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directing traffic from
one path to another.

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Switches will allow
you to manage

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traffic on your network
more efficiently.

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Routers are primarily about

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connecting to
different networks.

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If I want to connect
to the Internet,

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I usually do so
through a router.

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If I want to connect to
my branch in Minnesota,

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usually I connect to an

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external network
through my router.

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VLANs are going to give us

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benefits of both
switches and routers.

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A VLAN is going to
be a virtual LAN,

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so we'll be able to segment

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our network into
different subnets,

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if you will, and we
can do so on a switch.

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We'll talk about why
that's desirable later.

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Then of course, we
have to consider

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wireless access and
wireless access points,

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and how we'll allow
these hosts to

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connect without being
physically wired in.

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Another thing to
consider is VPN servers,

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and with wireless and VPN,

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we'll talk about those
ideas when we get to

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the remote access section.

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Every one of these terms
we'll go into more deeply.

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The next thing we have to
have if we're going to

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allow communication
is a protocol.

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A protocol is really
important because you could

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think of this as the language
that computers speak,

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and we have to speak
the same language.

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Quite honestly, that's not

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the best definition
you're going to hear.

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But it is a good way
to think about it

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because if I'm speaking

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Greek and you're
speaking Spanish,

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we're not going to be
able to communicate

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unless we have a translator.

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The more translators we have,

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the more unreliable
the communication is.

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If you ever want to
do something fun,

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use Google Translate to speak

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a phrase and translate
it into Spanish,

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then take that Spanish phrase

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and translate it
back to English,

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then take that result and
translate it back to Spanish.

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Do that about 10
times and you'll

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find the end result
is hysterical.

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By the end, you don't have

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anything you were
originally communicating.

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That's the problem when
it comes to protocols.

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When you have too many
different protocols,

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even though we can
get a conversion

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and can get a device
called a gateway,

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that's a protocol converter,

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we don't get good
true communication.

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What we like to be doing is to

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>> all use the same protocol.

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>> A better definition of
a protocol is that it's

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the set of rules or requirements

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that govern communication.

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Things like how much data
can be sent at once,

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how do I know if I'm sending

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more data than you can receive,

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how long should data
exist on the network,

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and how should the
packets be formatted,

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are all examples of information

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>> that make up a protocol.

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>> But again, from
this stand point,

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you can think of
it as a language.

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We have to share the language.

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The most common protocol
we have and use by

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far is the TCP/IP protocol.

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It's actually not a protocol.

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It's called a protocol
stack or suite.

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It's called a protocol
stack because it's

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made up of a lot of
little protocols.

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As a matter of fact,
you already know two of

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these protocols, TCP and IP.

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There's also HTTP, UDP,
ICMP, LMNOP it feels like.

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>> There are a lot of

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>> protocols that make
up the TCP/IP suite.

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Each of them have a
particular purpose.

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Just like everything,
we're going to go

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over this in more depth later.

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The medium, cable
or the airwaves.

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With cable, there are

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three main types that
we use for networking;

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coaxial, twisted pair,

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and fiber optic cable.

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Each of these are in use today,

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and they each have their place.

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We'll cover this in another
chapter where we get into

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more details and
specifics of mediums.

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We have to have cable or
airwaves if we're going to

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traverse because we need that
path for data to travel.

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Ultimately, what we talked about

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here is the fact that there
are a lot of elements

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that have to come together

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if we're going to
be able to share

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resources and communicate
across the network.

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At the very basic level,

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we have the systems
we want to connect.

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Then if we want a
domain environment,

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we have to have a network
operating system.

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That creates the
domain or the realm.

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We use connectivity
devices and protocols,

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that way we can agree
on how to communicate.

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Of course, there is media,

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which is what we traverse.

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Also mentioned here,

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we have certain network
services that we

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utilize like DNS and DHCP.