WEBVTT

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 So, in this video, I'm going to answer
 the question that you might have,

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 which is, why do I need to know really
 anything about applications if

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 I'm studying for my Cisco CCNA routing
 and switching application?

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 I mean, after all, my certification,
 I mean, after all, I'm studying to

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 learn how to configure, troubleshoot, and
 monitor Cisco routers and switches.

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 What do applications at layer 7 of the
 OSI model have anything to do with

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 that? First of all, you have to ask
 yourself, why do you want to be a

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 CCNA? You know, most people that are
 pursuing their CCNA certification

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 is because in some fashion, they want
 to gain employment in the world

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 of networking. They want to be a network
 administrator, maybe someday

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 a network engineer.

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 So, they want to be able to actually
 touch and start working on those

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 routers and switches that they see
 blinking away in the cages of their

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 company that they currently
 can't get access to.

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 So, that's the ultimate goal.

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 But a network administrator, if you actually
 do get that job or a network

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 engineer, can't effectively do their job
 if all they know about are routers

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 and switches. If that's all you know
 about, you don't know anything about

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 applications, it's going to be
 really hard to do your job.

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 Why is that? Well, because, you know,
 your job responsibilities as a network

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 admin or network engineer might include
 monitoring existing links for

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 bandwidth consumption.

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 Well, if you don't know what applications
 are in your network and you

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 don't know how those applications work,
 what their objective is, how often

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 they're expected to be active and doing
 something, how can you predict

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 how much network bandwidth is going
 to be used by those applications?

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 And if you can't predict that, how can
 you predict how much network bandwidth

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 you're going to need
 in your company?

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 You can't. Another job that you might
 have is implementing and monitoring

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 basic security policies
 with access lists.

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 Once again, if you don't know what applications
 are authorized and allowed

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 in your network, then how can you create
 and structure and implement access

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 lists to allow those authorized ones,
 but to deny or block the unauthorized

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 applications? You can't.

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 Similarly, troubleshooting problems in
 the network that could impact network

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-based applications.

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 You know, computer networks, you know,
 routers and switches can have a

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 variety of things that can go wrong,
 from completely crashing and dying,

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 to having congestion, to having jitter
 and delay, and a whole variety

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 of things, to routes, changing and
 shifting to different paths.

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 And all of those things impact applications
 to one degree or another.

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 It might cause the application not
 to be able to even start at all.

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 It might show up as an application
 starting but just sort of appearing

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 to be hung and not doing anything,
 or a variety of things.

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 So if you don't know what applications
 you have running in your network

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 and you don't know at a time when a
 problem occurs in the network, how

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 that's impacting the applications
 in your network.

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 So some of the questions that you're
 going to need to be able to answer

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 as a network administrator or network engineer
 are what are our applications?

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 You know, what is running
 in my company?

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 Are they client server or are they
 peer-to-peer applications?

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 And if you're not familiar with
 those terms, I'll go over that.

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 I'll explain what the
 differences are.

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 Are those applications
 TCP or UDP-based?

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 What port numbers are in use
 by those applications?

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 That's going to be especially critical
 if you're trying to track down

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 that traffic in a packet sniffer output,
 a wire shark output, or if you're

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 trying to implement security access lists
 and firewalls allowing and denying

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 certain applications.

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 Knowledge of the port numbers that they
 use is going to be critical for

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 that kind of thing.

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 Name resolution.

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 You know, a lot of applications out
 there have as an integral component

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 name resolution, where the application
 itself, you provided some human

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 readable name, and it needs to be able
 to resolve that name to a number,

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 usually an IP address.

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 So if the app, first of all, you'd have
 to ask yourself, is the application

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 I'm concerned with doing
 that kind of thing?

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 And in what circumstances would this
 application need to perform name

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 resolution? And when it's performing
 name resolution, how is it doing

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 that? Is there a file within a server
 somewhere that it looks up internally,

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 locally to itself, that resolves
 names to addresses?

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 Does it utilize DNS to do that?

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 We need to be able to answer
 those questions.

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 Where are the servers?

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 Okay, so once we know what applications
 are allowed and authorized on

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 our site, the next thing we have to
 ask ourselves is, okay, where are

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 the servers actually located that are
 required to make these applications

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 work? Are the servers on our site?


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 Are they actually in our campus
 and are building somewhere?

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 And if so, where are they?

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 Or are they hosted off-site?

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 Are we maybe using Amazon servers or
 some other cloud-based solution?

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 You have to know that in order to
 be able to troubleshoot problems.

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 And what security-related concerns
 do I need to know about?

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 In other words, where are
 applications allowed?

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 There might be certain applications that
 payroll uses that's really super

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 secret and only payroll is authorized
 to use those, so we need to know

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 that. So we can implement firewall and
 access list policies in other parts

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 of the network so that that application
 won't be sending data to parts

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 of the network it shouldn't
 have access to.

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 Are these applications supposed
 to be available 24 by 7?

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 Or are they only supposed to be available
 like at certain times of the

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 day? Ban with allowances.

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 You know, there's certain applications,
 for example, multicast.

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 If we're talking about multicast video,
 multicast video consumes a lot

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 of bandwidth, especially if we're talking
 about high-definition crystal

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-clear video consumes
 a lot of bandwidth.

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 So you might have to know, okay,
 is video allowed in my network?

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 What part of my network
 is it allowed in?

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 And how much bandwidth do
 I really want it to use?

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 Do I want people to be able to start
 and use video wherever, whenever

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 they want? Because if I do, I might
 end up accidentally starving out the

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 bandwidth of some other stuff.

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 Maybe some voice-over IP phone call
 will start dropping because there's

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 not enough bandwidth left for my IP
 telephony traffic or other types of

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 things. So we need to know, you know,
 what kind of bandwidth allowances

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 am I going to provide for the various
 authorized applications that are

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 in my network? And credential storage
 and administration for applications

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 that require credentials.

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 In other words, applications that require
 someone to provide a username

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 and a password or require someone to
 provide a digital certificate or

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 something. Where are those
 credentials stored?

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 Once again, are they on-site?

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 And if so, where?

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 Where is the server located?

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 What closet and what room?

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 How is it connected to the network
 where those credentials are stored?

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 Or is it off-site?

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 And if so, who's the contact I'm going
 to call if I have problems with

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 the credentials?

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 And also, what's my policy going to be
 if I discover that there's a rogue

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 application in the network?

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 Is my policy going to be that I'm going
 to let it keep going and I'm going

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 to monitor it so I can try to track
 down and be who's doing it?

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 Or is my policy that I'm going to have
 a firewall or an access list in

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 place so that it can't even start?


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 I don't even care about
 tracking it down.

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 It's just stop dead and can't
 even start in the first place.

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 Or some other policy, what am I going
 to do if I discover there's a rogue

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 application that I did not authorize
 running in my network?

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 So as a network administrator or network
 engineer, these are all application

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-related questions that you're going
 to need to deal with at some point

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 and you're going to need
 to be able to answer.

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 So in summary, a network admin doesn't
 necessarily need to know the intricate

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 details of how an
 application works.

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 In other words, you don't need to know
 the gory details of emails necessarily.

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 Maybe you actually are not
 the email administrator.

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 It's not your job to set up the email
 application, configure it, get all

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 the bells and whistles working so you
 don't have to know all the various

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 different options of
 your email system.

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 You don't have to know specifically
 the message types and message sizes

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 are going back and forth.

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 But you do need to know
 is email being used?

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 What kind of email is being used?

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 Who's allowed to use the email?

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 So without the information that we
 talked about the preceding slides,

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 configuring a network to meet predefined
 requirements would be impossible.

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 So hopefully by now you've got a pretty
 good idea of, okay, even though

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 I really love routers and switches,
 I probably need to know a little bit

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 about applications as well.

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 So that being the case, let's go into
 the next video where I'm going to

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 provide a high-level overview of the
 differences between TCP and UDP.