In this lesson,
we're going to discuss wired network topologies.
Now, a network topology refers to the arrangement
of different elements like the links, nodes, clients,
and servers that make up a computer network.
It is crucial that you understand
the different types of network topologies
when you attempt to design an efficient
and resilient network infrastructure.
Now, before we cover the six different types
of network topologies that we can use,
we first need to understand
how these topologies are going to be documented
in our network diagrams.
Generally, you're going to find
that network diagrams are going to document our topologies
using either a physical topology
or a logical topology.
Now, a physical topology is used to show
how the network devices and components
are physically cabled and connected together
using various types of copper or fiber media.
For example, if I wanted to show
where all the different network computers, routers,
and switches are located
inside of my office building,
I could get a copy of the building's floor plan
and then document where each of those devices
and those cables are located in that building
by drawing it over the floor plan for the office.
On the other hand,
we can also document our network
using a logical topology.
When we talk about logical topologies,
we're really talking about
how the traffic is actually
going to flow through our network.
On a logical diagram,
you're going to see where the workstations are,
where the routers are,
where the switches are,
and how all that stuff is going to be connected.
But this diagram doesn't actually show
the location of each device in the real world
by displaying it on top of a floor plan.
For example, just because a server is shown
in the upper right-hand corner of a logical diagram
doesn't mean this locate
in the upper-right hand corner
of your office building.
Instead, you may have several devices
that are shown on the logical diagram
that are located within the same room
or on different floors
or even in different buildings.
And it really doesn't matter
when you're dealing with a logical topology
because we just want to know
how they're connected logically in the network
and how the data is going to flow.
Within a logical topology,
I'm really just concerned with the way
that the data is flowing in the network
and not the way it's actually cabled
in the physical or real-world environment.
For right now, it's not really important
that you can understand or read these diagrams
or it's associated symbols and icons.
But instead, I just want you to realize
that there is a difference
between a logical and a physical topology,
and the difference is the one
is being focused on the logical
or network flow of the data,
while the other one is focused
on the physical layout of the cabling
and the devices in your real-world environments.
Now, I mentioned there are six different topologies
that we're going to cover in this lesson,
so let's take a look at point-to-point,
ring, bus, star, hub-and-spoke,
and mesh apologies as we continue on.
First, we have point-to-point topologies.
Now a point-to-point topology
is the simplest form of a network topology
because it involves a direct connection between two devices.
Point-to-point topologies are often going to be used
for connecting a computer to a network peripheral,
like a printer or a scanner.
While this is a straightforward
and reliable method for creating small-scale connections,
it's not really going to be scalable
for our larger networks.
Now, the only exception
to point-to-point topologies being used
in large enterprise-scale networks
is really for your wide-area network or WAN connections,
because you can connect
one of your company's remote offices in California
all the way back to your headquarters office in New York
using a point-to-point fiber optic connection
between those two facilities.
Second, we have ring topologies.
Now, a ring topology is a network configuration
where each device is connected to two other devices,
and this forms a circular data path.
In this setup, data is going to travel in one direction,
either clockwise or counterclockwise
until it reaches its destination.
Now, one of the benefits of using ring topologies
is that it's going to prevent data collisions
due to using this unidirectional flow.
However, if one node fails in the ring,
it can disrupt the entire network
unless there are redundant connections for failover.
Now, these days, ring networks are not very common
unless you're going to be using
a Fiber Distributed Data Interface
known as an FDDI or FDDI connection.
Now, a FDDI connection is going to be used
to conduct data transmissions
on fiber optic lines
in a local area network
and can actually extend up to
a range of about 200 kilometers,
which is about 125 miles in range.
Now, a FDDI ring is going to operate
on a dual ring structure,
and this provides redundancy
with a primary and secondary ring.
If the primary ring fails for some reason,
that secondary ring can maintain network operations for you.
FDDI is really well known for high bandwidth,
and this makes it really suitable
for environments with large data transfers
and high reliability requirements
such as campus area networks or data centers.
Third, we have bus topologies.
Now, in a bus topology,
all the network devices are going to be connected
back to a single central cable,
which is known as the backbone or the bus.
Data can be sent by any device
and it's going to be available
to every other device on that bus
but only the intended recipient,
which is identified by a unique address,
will actually process the message that it's seeing.
While bus topologies are really easy to install
and they require less cable than other layouts,
they do have some significant limitations.
The entire network can be disabled
if that main cable fails,
and as more devices are added,
the performance of that whole network will decrease
due to more data collisions happening on that cable.
Similar to a ring network,
bus networks are considered
to be an older technology,
and they're not commonly used
in our modern home office
or small office environments.
Fourth, we have the star topology.
Now, the star topology
is one of the most common network layouts
that's in use today,
and your own home network
is most likely using a star topology right now.
In a star topology,
each node in the network
is going to be connected
back to a centralized connection point,
which is normally going to be a network switch.
That switch can also act as a repeater
for your network's data flow.
This type of star configuration
is considered to be very robust
because the failure of one link
doesn't affect any of the other links.
However, the entire network
does depend on the functioning
of that centralized connection point,
that network switch that we just talked about.
So if that switch fails,
your entire network will become inoperable
if you're using a star topology.
Now, fifth, we have a hub-and-spoke topology.
Now, the hub-and-spoke topology
is a variation of the star topology
where the centralized node,
which we're going to call a hub in this case,
is connected to multiple nodes,
which we call spokes.
These spokes are not directly connected to each other,
so they must transmit their data to one of the hubs
before that data is going to be forwarded to another hub
and then onward to the final destination node in that spoke.
This layout is commonly used in airlines
as well as in telecommunication networks.
For example, if I wanted to take a flight
from Orlando, Florida, over to Honolulu, Hawaii,
I probably am not going to be able to find
a direct point-to-point or nonstop flight.
Instead, I may choose to fly on Delta,
which will then fly me
from Orlando over to Atlanta,
which is one of their hub cities,
and then I'll switch planes.
I'll get on that plane
and fly to Los Angeles,
which is another one of Delta's hub cities.
And then from there,
I'll switch onto another plane
and I'll take that plane
from Los Angeles over to Hawaii.
Now, if I instead decide to fly with American Airlines,
they use a different set of hubs
for their hub-and-spoke model.
So I might go from Orlando
over to the American Airlines' Dallas-Fort Worth hub,
and then switch planes in Dallas
and board a long flight
all the way out to Hawaii from Texas.
In either case, because we're operating
under this hub-and-spoke model,
the other passengers can be flying in
from all of the other cities
around the U.S. to that hub,
and then we'll all get on the plane together
and go from that hub over to Hawaii.
This is exactly what happens
in the hub-and-spoke model
when we're dealing with our networks as well.
Now, this means that we're going to be able to consolidate
a lot of our smaller regional offices
in one region like the Northeast
over to a hub, maybe in New York City,
and that way I could take the data
from the New York City office
and send it all the way over
to our Los Angeles office,
which is another hub,
and then from there,
it would spread out to the other
regional offices in California.
By doing this,
we can have these two larger data centers
having a really big, high, fast,
high bandwidth connection
that can transfer all the data for us very quickly
from those smaller regional offices
all the way across the country.
And this can save us a lot of money
by not having to connect
every one of those smaller offices
to each of the other smaller offices
all over the country
because those long distance links get really expensive.
Sixth, and finally, we have the mesh topology.
Now, the mesh topology is going to feature
a point-to-point connection
between every single device on the network
to create a robust and redundant network.
Now, there are two types of mesh topologies
you need to consider.
A full-mesh and a partial-mesh.
Now, a full-mesh topology is one
where every node is connected
to every other node in the network.
This topology provides high redundancy,
but it can be very expensive
and complex to install
because of the number of cables and ports required.
For example, if I have three nodes I need to connect,
I can create this full-mesh
by cabling node one and node two together,
then I cable node two and node three together,
and then I cable node one
and node three together.
This means, for three nodes,
I only need three cables.
That's not so bad.
But if I simply double the number of nodes
from three to six,
I'm actually not going to double
the number of cables required.
Instead, if I have six nodes,
I'm actually going to need 15 connections to ensure
that every node can communicate directly
with every other node.
This is because the number of connections we require
is going to be represented by the formula,
n times n minus one divided by two,
where n is the number of nodes.
So if I have three nodes,
it's three times three minus one divided by two.
This would equal three times two divided by two,
or three.
Now, if I have six nodes, on the other hand,
I'm going to have six times six minus one divided by two.
This would give me six times five divided by two,
which then turns into 30 divided by two,
or 15 different cables.
You can see how impractical this can be
when you start having a network
with a large number of nodes.
So to get the benefits of a mesh network
without having to create a full-mesh network,
we can opt to use what is called
a partial-mesh topology for our networks.
Now, a partial-mesh topology
is a less interlinked version
where some nodes are organized
in a full-mesh scheme
while others are only connected to one
or two devices inside of the network.
So if I have six nodes,
I may decide that only three of those nodes
are my most critical ones,
and they're going to be the ones
that are fully-interconnected in a mesh topology,
while the other three are considered less important nodes,
and they may only connect back to one
or two of those critical nodes
to send their data
between all the different nodes
in that partial-mesh.
So remember, understanding the different types
of wired network topologies is crucial
for network design and management.
Each topology has its
unique advantages and disadvantages
that makes them suitable for various scenarios.
Point-to-point is considered to be simple
and reliable for small-scale connections,
but it's not practical
for larger enterprise networks
most of the time.
Ring and bus topologies will offer simplicity,
but they can be vulnerable
to single points of failure
because you can have the ring cut
or the bus cut,
and that will stop all the communication on that topology.
Star and hub-and-spoke topologies do a good job
of giving you centralized network management,
but they do rely heavily
on the functioning of that central point,
which we call the hub in the hub and spoke,
or the switch inside of our star topologies.
And lastly, the mesh topology
offers robustness and redundancy,
but it can be complex
and costly to implement
because when you're doing a full-mesh,
you have a lot of connections
between all of those nodes.
In a partial-mesh, you're giving up
some of that resiliency and redundancy
in terms of lower cost and higher scale.