Lesson video

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Hi, I'm Allen your computer teacher for this key stage four network unit.

And this is lesson six.

This one is all about network speed and performance.

You will need a pen and paper for this lesson as you've to write down some answers for some of the activities.

Turn off all notifications on mobile phone so you're not disturbed.

Remove any distractions that are nearby.

And when you're ready, we can make a start.

Okay, this lesson will describe how network data speeds are measured and the impact they can have on performance.

We'll define what virtual networks are and how they can be used to maintain network performance.

And we'll explain why networks are a target for criminals and some of the means they use to do this and what we can do to protect ourselves.

Here's a question for you to think about for a second and you can pause the video if you want to write down some answers.

What are some of the things that might impact the performance of the network? So I'll give you a couple of seconds to have or a couple of minutes to have a think and then you can resume the video.

So what kind of ideas did you come up with for the things that might impact the performance of a network? Hopefully it was things like, the more devices you have on the network or the kind of activities that those devices are doing.

Let's take a look at network data speeds and latency.

Well, network speed is measured in bits per second.

So or BPS, you might see that.

And most modern LANs support one gigabit per second.

So that's over a billion individuals zeros and ones per second.

This is known as network capacity and it's the highest available speed.

It's not the actual promise of the speed you will receive.

Next we have network latency.

Well, this is a measure of the delay that the data takes and it's usually measured in a round-trip side fashion.

So, you send the data and it comes back to you.

So what's the measure of delay that that communication took and that's measured in milliseconds.

Because TCP IP acknowledgements need to be received for the data to continue to be sent, this latency drives what's called network throughput and this is the amount of data that can be transmitted by TCP IP.

So for instance, one second of latency, one TCP window, it's about 64 kilobytes of data.

If you reduce the latency, you can transmit more data per second.

This means a low latency will increase the amount of data TCP IP can send over the same timeframe.

Even with the network capacity of one gigabit per second, if the throughput is lower than the capacity due to latency, then you'll only get the available speed that the throughput offers.

If your network capacity is lower than the throughput, then you can only achieve the network capacity as a maximum.

So let's take a look at broadcast traffic.

In network, a broadcast is a method of sending a communication to all nodes on a network.

So for instance, a DHCP wouldn't be possible if broadcast traffic weren't allowed.

But it's not only DHCP that uses broadcast, ARP or the address resolution protocol, also use it to map hardware addresses to IP addresses.

However it can easily get out of control.

The more computers that run into the network, the broadcast traffic can become so large that it severely impacts the performance of the network.

If all the clients on the network are busy receiving and ignoring broadcast traffic that's not meant for them, then this reduces the available throughput on the network and slows down the network overall.

We can reduce broadcast traffic.

We can move from hubs to switches.

So by doing this, switches record the Mac addresses of devices so once a device has been found, the switch does not need to broadcast any more to find it.

We can also reduce broadcast traffic by ensuring all the services that we don't require are switched off.

So for instance, there's no point having a device broadcasting that it can offer a service that none of the devices require.

Monitoring the network can also reduce the amount of broadcast traffic that's going on.

There are tools available to administrators so they be able to see the type and amount of traffic that's being transmitted on the network.

It's really important that you also identify any faulty devices and remove those from the network as well.

Once the device becomes faulty, it can inadvertently start to generate broadcast traffic that eventually slows the network down.


So using the information you've just been given, there is a task to complete.

This is task one and it's called true or false.

So using the worksheet decide whether the statements about broadcast traffic are true or false.

You can pause the video and complete the task.


How did you get along? Well, the top comment, if there are too many computers added to a network the amount of broadcast traffic reduces.

That is false.

The amount of broadcast traffic wouldn't reduce it would actually increase.

Broadcast traffic can be controlled by moving from hubs to switches.

That is true.

Faulty devices have little to no impact on broadcast traffic.

That is false.

As we said, identifying and removing any faulty devices is important because they can start to generate lots of unwanted broadcast traffic.

Broadcast is a method of transmitting a message to all nodes on the network simultaneously.

We decided that was true.

And this is the same way that DHCP works as we discussed earlier on.

And ARP, address resolution protocol, is used to find devices and map IP addresses to hardware addresses.

And that is also true.

So hopefully you got all those right.


Here's another question for you and you can pause the video briefly if you'd like to.

What do you think the acronym V L A N stands for? So VLAN.

What do you think that stands for? Okay If you got an answer.

Well it stands for virtual local area network.

So what are VLAN and why would we use them? Well, they're software-defined networks.

It means that the networks that are configured and maintained in the software of the network switch.

They operate across multiple switches.

This means that a VLAN can combine network devices together in a single network even if they're not connected to the same switch.

They segregate or direct traffic.

So VLANs can be used to segregate network traffic and clients from each other, or when combined with routers, they can be used to determine what type of traffic is allowed to flow from one VLAN to another.

A VLAN header is added to each packet.

The switch or network device adds a special VLAN header to the head of the packet of data and this instructs the switch, which VLAN the data belongs to.

The switches they're responsible for moving that data into the correct VLAN as part of the VLAN defined software.

We also use them to contain the scope of the broadcaster domain.

So by limiting the number of devices in a virtual LAN, we can reduce the amount of broadcast traffic that's transmitted across that domain.

We can also use them to group noisy devices together.

So some devices can generate lots of traffic and inter-device communication.

By segregated these devices into their own VLAN, the rest of the network is not impacted by this noise.

We can also prioritise certain traffic over other traffic.

So some services, for instance voiceover IP and video cameras require uninterrupted network bandwidth for obvious reasons.

And this ensures that this video or voice call is not broken up.

By assigning these devices their own VLAN, it's possible to programme the switches to prioritise this type of traffic on the network.

VLAN are also used to secure networks from one another.

So we can separate parts of the network from other parts.

So for instance, one example of this would be guest wifi.

If you go anywhere and you can log onto free wifi.

This is often part of its own, it's got its own VLAN and it's separated away from the rest of the main network for that organisation.

Ultimately it's cheaper.

So without VLAN, each separate network would require its own switches and cabling.

By defining these network using the software on the switches, we're able to create these extra networks virtually without the need for buying more equipment.


So task two.

Advantages of VLAN.

Using the worksheet, write down some of the advantages of a virtual local area network.

You can pause the video and complete the task.


Hopefully you got advantages down as to what and why we use VLANs.

The next topic we're going to look at is keeping network safe.

And we got task for you straight away.

There's a worksheet to complete.

And what I want you to think about is why do criminals target networks and what are the some of the ways that they do it? Okay.

So you've got worksheets to fill in.

You can pause the video and complete the task.


So why do criminals target network? Well here, we've got three broad reasons split up.

You can gain prestige in the hacking community for saying you've compromised a challenging network or you may be protesting or cyber protest or internet activism.

And these are ways is basically stealing stuff.

So whether that's monetary information, bank details, credit card details or it could be stealing identity information so somebody can commit identity fraud or it could be stealing intellectual property, so data on an organization's computer that they can use to sell onto someone else or perform a crime with that further on down the line.

We've also got stealing government secrets.

So government secrets can be used for instance, to influence elections.

And I think we've seen some of that in the news in recent years about, they're using information on the internet to influence elections.

But how do they do it? Well, some of the of the ways that they do are linked here.

So we've got something called phishing with a ph, and that's tricking a user into sharing their username and password.

So you tend to get these in emails purporting to be from somewhere else and it looks legitimate.

So it might look like it's from Netflix or it might look like it's from PayPal or your bank.

They'll say, "click here" and you'll click there to log in and you'll put your username and password in and that username and password go straight to them and they've now got your username and password for that account.

Problem with that one is, if people tend to use the usernames and passwords the same ones for multiple accounts which you shouldn't do, so don't do it, but if people do do that, then they've got a chance to be able to access other accounts using the same details.

The other way that cyber-criminals attack networks is to use a virus or a Trojan.

And this will allow them to gain access to a system, again to either steal information that they can use or further down the line, or they can use this to create further attacks on the network and then that obviously spreads and becomes more prominent and causes more problems. They can create distributed denial of service attacks.

So this is where a computer will just repeatedly or a group of computers will repeatedly send data to the target's computer, flooding the system to the point where it becomes unusable.

This is often using internet activism, and it's used to take certain websites offline for a certain amount of time, and then that gets that group that have done that or that person a little bit of a bit of notoriety or a little bit of publicity.

Cyber criminals can also attack computers using vulnerability exploits.

So for instance, there may be holes in the software or you know areas in the software that are known and then they can be exploded to gain access to the data or destroy the data even, that's contained in those systems. So how can we protect ourselves against all these problems from cyber attacks? Well, antivirus software.

That's probably a great place to start making sure that your antivirus software is up to date and then if you do potentially get attacked, then that software will remove the virus and stop it accessing your files.


So this is software that restricts access to networks and computers by defining what IP addresses and networks are allowed to communicate with those ports.

Generally computers are used around firewalls, but you'd normally do have one in the perimeter of an organization's network too.

Make sure that system and security updates are always installed.


So if ever your PC or your mobile phone says that there is a security update or a software update, it's always best practise to update that as soon as possible to make sure that you've got the latest fixes to any vulnerabilities that have been spotted.

And the really useful one is to implement two factor authentication wherever you can across your devices.

So, when you're logging into somewhere, you then need a secondary physical device to kind of verify that the username and password that's being used is being used by you, and you can verify it from another device before access is granted.

Lastly, we have penetration testing.

So some companies employ people to actually try and break into their systems or to hack into their system.

So legally hacking.

It's cheaper to find somebody to do that for them than it is to suffer the consequences of a hack.

Once there's a vulnerability that's been spotted in the network, they can take steps to protect themselves from that in the future.


That's it for the key stage four network unit.

I hope you enjoyed it and hope you've got a lot from it.

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