Instructor: In this lesson,
we're going to talk about network performance issues
and how you can troubleshoot them.
Now, when I talk about network performance issues,
we're talking about anything that is manifesting itself
as a slowdown inside of your network.
This can be experienced on the client itself
or numerous clients across the network
or the entire network.
It really does depend on what the issue is.
Let's take a look at a couple of different issues
and how you can solve them.
First, we have the issue of a mismatch duplex setting
on either your network interface card
or your switch port interface.
Now, when I talk about the duplex,
there is two different settings you can have.
This can be set as half duplex or full duplex.
Now the older legacy setting is what's known as half duplex.
In the very first computer networks,
these networks could only either send
or receive information, but not both at the same time,
and this is what's known as half duplex.
If you've ever played with a walkie-talkie as a kid
and you pick it up and you press the button
and you start talking,
at that time, the other people in line cannot talk.
They can only listen because it cuts off their connection
from them being able to send any information.
That is what's known as half duplex.
You can send or you can receive,
but you can't do both at the same time.
Because of this, your network speed
is going to be cut essentially in half
if you're operating in a half duplex.
Now, half duplex was the standard
any time you were dealing with hubs in your network,
but once we upgraded to switches in our networks,
half duplex was no longer necessary,
and instead, we could operate in full duplex.
Now, full duplex means you can send and receive data
at the same time,
and this effectively doubles your network speed
because you're operating in this full duplex mode.
Now, the reason that full duplex can operate
when you're using a switch is that every single switch port
is its own broadcast domain,
and this means the switch knows that nobody else
will be interrupting it,
and similarly, your network interface card
knows that nobody's going to interrupt it
when it's sending things to the switch,
And this allows us to operate in this full duplex mode.
Now, by default, most of our network interface cards
are set to do what's called auto negotiation
when they first connect to a switch port.
During this auto negotiation process,
they're going to figure out are they going to operate
in half or full duplex mode.
And this is a negotiation between the switch port interface
and the network interface card,
and they will determine between themselves
which one they can support.
They both would prefer to be operating at full duplex,
but if either of those is set to half duplex,
the other one will comply with that,
and therefore, you'll be in a half duplex mode
and this will slow down your system.
So if you check the network interface card settings
or your switch ports interface settings
and you see that either one is set to half duplex,
this will be a great indication
of why you're experiencing these poor network speeds
and you'd want to be able to switch both of those
back to full duplex so you can operate
at a more efficient level.
The second area we have is a mismatch speed setting.
Now the speed setting is a little bit different
than the duplex setting,
but it goes back to the same basic concept.
When your client tries to connect to the network,
your network interface card and the switch ports interface
are going to do an auto negotiation.
As part of that, they're going to figure out
are we going to use half duplex or full duplex?
But in addition to that, they're also going to figure out
what speed the two cards are going to speak at,
whether that is going to be 10 megabits per second,
100 megabits per second, or 1,000 megabits per second
depending on the card
and the switch that you're connecting to.
This is because all of our network interface cards
are backwards compatible,
so if you're connecting to a one gigabit per second switch,
your network card should be able to operate
at 10,00 megabits per second,
which is one gigabit per second,
if it's going to be able to work at its highest level.
On the other hand, if you connect to a legacy switch
that only operates at 100 megabits per second,
your gigabit ethernet card will downgrade itself
to a 100 megabits per second card
during that auto negotiation process.
Now, normally this works great
and both devices can figure out what the highest speed is
and they'll both select that,
but sometimes there is a mismatch here
and this will cause the speed to go down.
In this case,
even though you're using a gigabit ethernet card
and a gigabit switch,
there might have been some interference
during that negotiation process
and they've now downgraded themselves
to 100 megabits per second or even 10 megabits per second.
And this will drastically decrease
your performance over the network
and you'll see much lower network speeds.
Now to solve this issue, you're going to want to log in
and look at the settings on both your network interface card
and your switch port interface
and make sure they're both either set to the auto setting
or the highest setting they can support
so you can maximize your performance.
Now, the third thing
that can cause performance issues for you
is if your network adapter driver is really old
and needs to be updated for better performance.
This happens over time, where the older drivers
no longer work as efficiently on modern networks.
So if you have an older computer
or an older network interface card
and you're using a driver that's several years old
and you're seeing low performance,
you may want to go and check that driver
and see if there's a more updated version
that provides better performance.
Remember, software drivers are installed
within the operating system to tell your computer
how to interact with these different expansion cards,
including network interface cards.
So if you're using an older driver
and it doesn't have as good a compression or speed handling
or things like that, this can actually lead
to a lot of performance issues for you,
and by updating that driver card,
you're going to be able to get better performance
so that you can have higher network speeds.
And the final area
that can cause network performance issues for you
is if your client has a malware infection.
If you get infected with malware,
that can do a couple of things to your client system.
For example, it can start eating up processes
in the background,
which is going to slow down the entire computer overall
and in turn, your network.
For example, it can actually start
eating up processes in the background
which takes away compute time.
When this happens, it's going to slow down the entire computer,
including the ability to send and receive data
over the network.
Alternatively, you might see that a malware infection
is being used as part of data exfiltration.
Now, data exfiltration is just a fancy term
for saying that we're going to be sending data
in the background without the user seeing it.
As a hacker or an attacker, our goal is to get data
from your computer back to our servers,
and when we do that, that is called data exfiltration..
Now, data exfiltration
is going to use your network bandwidth,
so it's happening behind the scenes
and you're not even realizing it,
and if I'm sending gigabytes of data
through your network connection,
that will slow down your entire system,
and when you try to open up a web browser
and go to a website,
it's going to appear very slow because you don't realize
that most of your network connection
is already being used up in the background by this malware
that's sending and receiving data without your knowledge.
So remember, when it comes to network performance issues,
you can have a lot of different things happening
that can cause this.
It can be things like mismatched duplex settings,
mismatched speed settings,
network adapter drivers that are out of date,
or your system may be the victim of malware.
Now, in addition to that,
whenever you're troubleshooting a performance issue,
I want you to break it down into three main groups.
First, is this affecting just a single client?
Second, is this affecting a segment of the network?
Or third, is this affecting your entire network?
Now, based on identifying
which of these three categories it is,
you're going to be able to take different steps
to try to increase the performance.
If this is a single client issue,
then you're going to be looking
at its individual duplex settings, speed settings,
network adapter drivers,
and if it's been infected with malware.
But if you have an entire segment of the network
that's actually going slow, then it's most likely
that you're going to have a single switch that's involved
as that choke point
and you want to look at the settings on that switch
to identify why only those clients in the network
are having problems as opposed to everyone on the network.
And then the third category
is when you have the entire network slowing down.
Normally, if your entire network is slowing down,
it's going to be an issue
with the choke point at the edge of your network.
This would be your router, your gateway, or your firewall.
So you're going to want to look at those devices
and make sure that they are not becoming the bottleneck
for all of your network performance,
because if you're starting to have issues
and it's affecting the entire network,
it's got to be an issue with something
that does affect the entire network,
like the router, the gateway, the firewall,
or it could even be your weighing connection
is becoming overloaded because you have too much data
going in and out of your network at a given time
and you may need to consider increasing
the overall speed of your wide-area network connection
to ensure you're getting the best performance
for all of your users.