In this lesson,
we're going to cover some datacenter topologies.
Now, when we're talking about a datacenter,
this is any facility composed of network computers
and storage that businesses
and other organizations use to organize, process, store,
and disseminate large amounts of data.
Now, that is a pretty generic definition,
but that is because a datacenter is used to describe a lot
of different things these days, from very small
to massively large areas.
For example, at one of the smaller organizations I used
to work for, we had a small datacenter
that was roughly 150 square feet in size,
basically the size of a standard bedroom.
Within it, we had a single rack of networking equipment
and about five racks that contained our various servers.
On the other hand, one of the largest datacenters
in the world is located in Bluffdale, Utah.
This datacenter is known as the Utah Datacenter,
or by its official title,
the Intelligence Community Comprehensive
National Cybersecurity Initiative Data Center,
and it is 1.5 million square feet in size
and it spreads out across 20 different buildings.
This datacenter is so massive, it uses around 65 megawatts
of electricity just to power it.
This datacenter actually cost the US government
about $1.5 billion to build,
and they spend over $40 million each year
just on the electric bills.
Now, personally, I have worked
at some really large datacenters,
but nothing in comparison to the size
or scale of that one.
Amazon, for example, uses datacenters that range in size
between 150,000 to 215,000 square feet,
and each of these datacenters can host about 50,000
to 80,000 servers inside of it.
Now, as a network technician,
you may very well end up working at one
of these large datacenters one day, so it's important
that you understand the different topologies
or architectures that they're going to utilize,
including the three-tiered hierarchy, a collapsed core,
the spine and leaf architecture,
and the different traffic flows that are used inside
and into our different datacenters.
Now, first, let's take a look at the three-tiered hierarchy,
which consists of the core, the distribution,
or aggregation layer, and the access or edge layer.
Now, the core layer is going to consist of the biggest, fastest
and most expensive routers
that you're going to end up working with.
This core layer is considered to be the backbone
of our network, and they're used
to merge geographically separated networks back
into one logical and cohesive unit.
In general, you're going to have at least two routers
at the core level, and they're going to operate
in a redundant configuration.
After all, if you only have one core router
and it goes offline, your entire network is going to grind
to a halt and stop functioning.
Next, we have the distribution or aggregation layer.
This layer is located under the core layer,
and it provides boundary definition
by implementing access lists and filters.
Here at the distribution
or aggregation layer, we're defining the policies
for networks at large.
Normally, you're going to see layer three switches being used
at this distribution layer to ensure
that the packets are being properly routed
between different subnets
and VLANs within your enterprise network.
Finally, we have the access or edge layer.
This layer is located beneath the distribution
or aggregation layer, and the access
or edge layer is going to be used to connect all
of your endpoint devices, like computers, laptops, servers,
printers, wireless access points, and many others.
These access or edge layer devices
are usually going to be regular switches,
and they're going to be used to ensure
that packets are being converted to frames
and delivered to the correct endpoints.
Now, you may be wondering,
why do we need this three-tiered hierarchy?
Well, by using this type of hierarchy,
we can get better performance, management, scalability
and redundancy from our networks.
This also gives us a better way to troubleshoot our network
because normally if there's an issue, we can isolate it down
to a single access or edge layer device.
Now, once we've isolated it down to that single device,
we can work on fixing it while the rest
of the network can continue to operate unimpeded.
Now, normally in your datacenter,
you're going to find your core layer devices,
as well as your distribution or aggregation layer devices
for the local network in that building.
If you have remote branch offices or other locations,
each one of those will have its own distribution
or aggregation layer inside of its main distribution frame.
In both cases, your network will then branch out
into the intermediate distribution frames
where you're going to find the access or edge layer devices.
Now the second thing we need
to talk about is the collapsed core.
In datacenter topologies,
a collapsed core design is going to refer
to a network architecture where the core
and the distribution layers are being merged
into a single layer.
This basically gives you a two-tiered system,
also known as a collapsed core.
Traditionally, network designs consist
of that three-tiered hierarchy we just talked about
with the core, the distribution and the access layers.
But in a collapsed core design, the functions
of the distribution and core layers are going to be combined,
and this simplifies our architecture.
This is often seen in smaller
or medium-sized datacenters with a scalability offer
by a full three-tiered model is just not required.
The collapse core model is going to reduce the number
of switches that you need, and this can lower your costs
and simplify your management.
The collapsed core model also reduces latency
by decreasing the number of hops
between devices and the core of the network.
However, while a collapsed core design does offer simplicity
and cost savings, it may not be suitable for larger,
more complex networks where the distinction and scalability
provided by separate core and distribution layers
are going to be more beneficial for us.
The choice between a traditional three-layer model
and a collapsed core
is going to depend on the specific needs
and size of your datacenter.
Third, we have the spine and leaf architecture.
Now, the spine and leaf architecture is an alternative type
of network architecture
that's used specifically within our datacenters,
whereas the three-tiered hierarchy we covered
was going to be used to connect the core layer down
to the distribution layer, and then down to the access
or edge layer with all the endpoint devices.
The spine and leaf architecture is simply going to be focused
on the communication within the datacenter itself,
and specifically looking at server farm portions
of that datacenter.
Now, the spine and leaf architecture consists
of two switching layers known as the spine and the leaf.
The leaf layer is going to consist of all the access switches
that are going to aggregate traffic from the different servers
and then connect directly
into that spine layer or network core.
This spine connects switches
that are going to interconnect all the leaf layer switches
into a full mesh topology.
This leads to increased performance
and redundancy for all these servers
that are going to be connected to the leaf layer
and in turn to the spine layer.
By using a spine and leaf architecture,
we can actually get faster speeds and lower latency
than using a traditional three-tiered hierarchy.
By using the spine and leaf architecture,
we're going to be able to take shortcuts in getting data
from one place to another and this happens best
when we're using software-defined networks
in combination with a spine and leaf design.
Now, if you're installing a spine and leaf architecture,
normally you're going to install two switches
in each of your server racks.
This is normally called top of rack switching
because the switches are physically installed
at the very top of your server rack,
and each server in the rack will have a connection to each
of those two switches
that are located inside the server rack.
These switches are essentially the leafs
in our spine and leaf architecture,
and they connect back to the spine,
which serves as our backbone
inside of our datacenter network.
Now, alternatively, you can actually connect this spine
and leaf architecture in combination
with the standard three-tier hierarchy.
Under this model, all the servers in the datacenter
are going to connect to leaf layers,
and the leaf layers will connect to the spine.
That spine then connects directly to the core layer
of your three-tiered model
where all the other non-datacenter devices
will instead connect back to access or edge layers
and then to the distribution or aggregation layer
before going back into the core layer.
Fourth and finally, we need to discuss traffic flows
in relation to our datacenters.
Now, there are two main types of traffic flows.
We call these north-south, and east-west.
Now, these two terms are going to be used
to describe the direction of the traffic flow,
either into or out of a datacenter or across a datacenter.
When we have north-south traffic or communication,
we're referring to traffic that enters
or leaves the datacenter from a system physically residing
outside of that datacenter.
When we specifically talk about north traffic,
this is the traffic that's exiting the datacenter.
Southbound traffic, on the other hand, is referring
to traffic that's entering your datacenter.
In both of these cases, the data will be exiting
or entering the datacenter through a firewall
or other network infrastructure boundary, such as a router.
Conversely, we also have something known
as east-west traffic.
Now, east-west traffic or communication
is instead going to refer to the data flow
within your datacenter.
For example, if we're using a spine and leaf architecture,
any data flow between various servers in the datacenter,
even if it goes between different leaves,
would be considered east-west traffic.
Now, due to the increased use
of software-defined networking, virtualization,
private cloud and converged networks,
more and more traffic is being classified
as east-west traffic
because it's all existing within that datacenter
or that virtual datacenter
if you're using cloud computing like AWS, Azure
or the Google Cloud Platform.
Simply put, if your data is entering the datacenter,
it's considered southbound traffic.
If it's leaving the datacenter,
we consider this to be northbound traffic.
If it's moving within your datacenter,
we consider this to be east-west traffic.
So remember, there are many different ways
to architect your datacenters
and networks using either a three-tiered traditional model,
a collapsed core model, or a spine and leaf architecture.
And in any of these cases, you still need to understand
how the traffic flows in, out
or throughout your datacenter.
When you're choosing a datacenter topology,
which one you decide to use will really depend
on your business case and your organization's needs,
so make sure you consider those as well.