When you're designing, building or troubleshooting a network,
you'll be using a network topology
type that can vary depending on the technology you're using.
If you're looking to understand the way the data is flowing
or you want to plan to create a new type of network,
then it's useful to understand what these topologies might be.
This is also useful during the troubleshooting process,
because you'll know exactly what flow
the traffic takes to get between point A and point B.
One of the most popular types of topologies
is the star topology.
You might also hear this referred to as a hub
and spoke, where the hub is in the middle
and the spokes are along the outside.
This is a topology that you'll find on
almost any network regardless of the size of the network.
And you'll also find that most devices are connecting back
to the central hub of the star.
For example, a switched ethernet network
has the ethernet switch in the middle of the star.
And then all of the devices run directly back
to this particular switch.
They're not connecting to each other.
They're instead connecting back to the central switch
in this star topology.
Although we don't often see a ring topology used
on our local area networks, it's still
a topology type that's used quite often for wide area
networks.
So although many people will remember the older token ring
technologies that we used to run inside of our local area
networks, we don't generally find those ring networks
any longer.
But if you're connecting over a metropolitan area
network or a wide area network, we
use ring networks extensively.
It's not because a ring technology somehow
lends itself to work better over a wide area network.
It's because we can create additional redundancy
using the ring topology.
For example, a very common way to send traffic
over a ring network is to have the traffic simply go
in a circle.
Now if we're on this wide area network
and there's construction going on
and someone happens to sever a fiber connection that's
being used for this metropolitan area network,
then we're not going to be able to send that traffic
through the rest of that ring.
But the devices that are on either side
of that severed link recognize that traffic
is no longer able to traverse that connection
and instead will loopback the connection
on those individual endpoints.
So instead of having data go around a ring,
the data will instead go to as far
as it can around the ring and then
loopback to get to the other side of the ring,
maintaining uptime and availability even in the case
where part of that ring may be severed.
Early types of ethernet networks were not switched ethernet,
but were instead run over coax.
And this coax was quite simply a cable
that was run down the middle of the room very similar
to this cable.
This is a bus network.
And although it was commonly used
on those early ethernet networks,
we can still find modern networks
that use the same bus topology.
One problem with bus networks is that it is a single cable that
is running either through the walls
or down the center of the room.
And if we happen to have a break in this cable,
you can see immediately that it would suddenly
segment the network into different pieces.
Or in some cases, cause no data to be
transferred across the network.
That's one of the reasons we moved away from bus networks
for our local area networks, because one single disconnect
could cause an outage for everybody else on the network.
In our modern automobiles, we have bus networks
that we use extensively.
These are controller area network buses, or CAN bus
connections.
And they're used to connect all of the different sensors
and controllers inside of our automobiles
to be able to make all of our cars much safer
to drive on the roads.
Another popular topology, especially in larger networks,
is to create a mesh between devices
or a mesh between sites.
We may have devices that are connected
in different locations.
And we might want to connect them all together.
But instead of having a single connection
to a particular site, we may want
to create multiple connections to mesh these together.
That way if we do lose any one of these network links,
we're able to work around that problem by simply using one
of the redundant connections.
You'll commonly use this type of mesh design
if you're creating redundancy or fault tolerance
or perhaps you're designing a load balance network
and you can use different parts of the network
to share that load.
Probably the most common place to find a wired mesh network
is over a wide area network where
you can create multiple links to other sites
so that you can have a primary connection from one
site to the other and then a backup or secondary connection
that you can use if you run into problems.
When you start combining these different typologies together,
you create a hybrid network.
A hybrid network is more than one of these topology types
all working together.
For example, you might have three remote sites
all connecting devices together using a switched ethernet
or star network.
And then you may be connecting those together
over a wide area network that uses a ring topology.
If you're using a wireless network,
you may be communicating in a number of different ways.
If you're using an access point, you're
probably communicating over an infrastructure connection.
This means that all of the devices on your network
are communicating through an access point.
This is probably the most common way
to use wireless connections, but it's not the only way
to communicate over a wireless link.
If you just have two devices and there's no access point
that you can use, you can connect directly
from one device to another using ad hoc networking.
You don't need an access point or any other type
of wireless infrastructure.
You simply have one device communicate directly
to another device over this wireless connection.
And if you've added internet of things devices, which
are commonly wireless devices that control our lights,
our door locks, or the air conditioning systems, then
you're probably using a mesh network
where all of these devices can communicate
to all the other devices simultaneously
to create an interconnected mesh of communication between all
of these IoT devices.
One of the advantages of these mesh
wireless networks is that it allows
many devices to communicate to each other
even if those devices are very far apart from each other.
This also allows the mesh network to self-heal.
So if you turn off one of those IoT devices,
the remaining devices will self-heal and redesign
themselves into a mesh network that
will allow them to continue the communication.