With a peer-to-peer network, there's
not a server or a client.
Instead, every device is a server and a client,
so everyone is communicating to each other
to be able to gain access to the data that they might need.
This is a very easy way to deploy an application,
because you simply install it on everyone's computer,
and they all talk amongst each other
to be able to use that particular app.
You don't need an additional server.
You don't have to purchase and maintain that server operating
system.
Everything runs on everyone's existing systems,
so the cost is relatively low to implement.
One of the significant disadvantages of peer-to-peer,
however, is that it's very difficult to administer
this type of system.
The entire application is distributed.
All of the authentication process is also distributed,
so it's very difficult to be sure
that a peer-to-peer application will remain secure.
With client-server communication,
the responsibilities are split.
You have individual clients, and then
you have a centralized server, and when
clients need to access data, everyone
will access the same server.
As you can see by this diagram, clients
are not communicating to each other
directly, or even through the server.
All the clients talk to the server,
and the server talks to the clients.
This gives you very good performance,
because you have a direct connection to the server
that you can manage and maintain.
This also allows for easy administration,
because you can configure the application
and the authentication for that app at the central point
where the server is.
As you can tell with this diagram,
though, there's additional hardware and software
that you'll need.
You'll need a server, and you'll need somewhere
to store it and maintain it, and that has an additional cost
associated with it.
This also adds a bit of complexity,
because you have a centralized server that
needs to be administered.
That's something you don't have on a peer-to-peer system.
If you're working inside of an office,
or you're working from home, that network
that's in your office or in your home is a local area network.
It's local because the network that you're using
is usually within the same building
that you happen to be in.
This could also be the network that's
within a single building, for example,
between different floors.
That is a local area network, because all of those resources
are local to us in that building.
Generally speaking, a local area network
will have a relatively fast throughput.
We're using 802.11 wireless networks and ethernet
connectivity to be able to have high-speed communication.
If you find that you're using slower connections,
or it's a link that doesn't run at these higher speeds,
then you're probably not communicating
over a local area network.
Many companies will have buildings or parts
of their organization that are located
in different parts of a city to be able to communicate
to those buildings, we need to use a metropolitan area
network, or a MAN.
This is obviously a much larger network than something
that's in our single building, and it's usually expanding out
to a large, citywide area.
Usually, you're working with a third-party provider in that
city to provide this service.
Occasionally, you'll see this referred
to as metro ethernet for this metropolitan area network.
It's very common to see governments
use metropolitan area networks, because they're obviously
very geographically dispersed throughout the metropolitan
area, and they have right of way, so it's very easy for them
to put fiber in the ground and connect up
all of their remote locations.
If you're going outside the scope of a metropolitan area
network and communicating over a much larger distance,
then you're probably using a wide area network, or a WAN.
One characteristic that tends to be very common when you start
expanding the distance of these networks
is that the networks tend to become a little slower
in their throughput.
So wide area networks generally don't
run at the same speeds as a local area network
that you might have in your building.
If you're connecting over an MPLS
network or point-to-point serial WAN connection,
then you're almost certainly communicating over a wide area
network.
These can be links that are connecting us
with fiber that's in the ground, but we could also
use satellite communication, which is certainly a wide area
network, and those nonterrestrial links
would allow us to connect locations
that may be very far away.
A specialized type of local area network
is one that is wireless.
This is the WLAN, or Wireless Local Area Network,
and usually these are 802.11 networks.
If you're within a building and you're
walking from one side of the building to another
and you're connected to your local network,
then you're probably connecting over one
of these wireless LANs.
This is one that does have a limited geographical area.
When you leave your building, you're
probably not going to be able to communicate
to this WLAN because of the short distances associated
with 802.11.
But if you're in a larger area, there
are ways to extend this distance using multiple access points.
So you could be in an entire downtown area
or in multiple buildings and still maintain connectivity
to that wireless LAN.
If you have a Bluetooth headset, you're
connecting to your computer with a Bluetooth keyboard,
or using some other type of personal connection between you
and the devices you use, then you're using a personal area
network, or a PAN.
If you're in your car and you connect
to a speaker and a microphone or you play audio
through your phone to the audio system of the car,
then you're using a Bluetooth-based personal area
network.
We also consider that Bluetooth connection
to a wireless headset to be a personal area network.
And if you're using some newer workout equipment at your gym,
you'll find that is connecting to your mobile phone
using this personal area network.
There's a middle ground between a local area network
in a building and a metropolitan area network
that might connect us to a site that is many miles away.
We could have multiple buildings within our local area
on a single campus.
You certainly would see this with schools and universities,
but this could also be the same for large organizations
that may span multiple buildings in a particular area.
This is a campus area network, or a CAN,
and it's very common to have these buildings connected
with conduit, making it very easy
to pull fiber from one building to another
and connect all of your users to each other.
We would usually run some type of local area network
technology so we would have high-speed ethernet between all
of these buildings, so that we're
able to communicate as if we were sitting
all in the same building.
This is usually a connection that's made on private LAN.
You've put your own conduit into the ground,
you've run your own fiber connection,
so usually there's not a third party
that needs to be involved.
There wouldn't be a monthly payment to an internet service
provider because you're the one that has built the conduit,
you've run your own fiber, and you don't
have to involve a third party.
One of the reasons for adding all of these connections,
especially on local and wide area networks
is so that users can have access to their data
usually this data is located in a central location
and we're usually storing it on something
like a network attached storage device, or a NAS.
This NAS contains multiple drives
and is able to store large amounts of data
in this one single area.
A network attached storage is usually
a device where you can access these files at the file level.
File-level access means that any changes you make to this file
have to be done to the entire file that's
located on this device.
This means if you have a file that's a gigabyte in size,
and you just need to change one byte within that file,
you have to overwrite the entire gigabyte,
because you're using a network attached storage.
If you just wanted to change that single block of data that
contained that information, then you
would want to use a storage area network, or a SAN.
To your computer, a SAN looks and feels
a lot like the local drive that's on your system.
So being able to make block-level changes
to this information can be done very quickly and very
efficiently when compared to something like a network
attached storage device.
Whether you're using a NAS or a SAN,
you're probably going to be sending and receiving
a lot of data to these devices.
For that reason, you would probably
have a dedicated network for the storage area networks
or network attached storage devices,
and you would probably connect these with the fastest network
possible.
Through the years, we've had a number of different wide area
network technologies.
We had frame relay and ATM, and as our needs changed
and the way we use these networks changed,
we needed a smarter way to communicate.
So we created MPLS, Multiprotocol Label Switching.
This is communication through the WAN,
but it uses labels to be able to determine
how we route and forward that traffic through the WAN.
One advantage of MPLS is that we can
use almost any type of connection for MPLS
and we can put almost any type of data inside of an MPLS
network.
This means that we could send IP traffic, ethernet frames,
or any other type of data we'd like through the MPLS network.
This makes MPLS relatively easy to get up and running
and have all of our data transferred
between two locations.
With IP routing, we're always concerned
about the IP subnetting and the next hop
that we're going to use.
But with MPLS, we make forwarding decisions
based on the label switching.
This label switching is something
that's added when we put information
into the MPLS network.
If we have data and we have information
on one side of the network, and we
would like that data to get to the other side of the MPLS
network, we send that data into the first provider edge
router that's closest to us.
That edge router is going to insert a label into this data.
We call that pushing the label onto the data.
It's going to then know how to forward
that traffic through the internals of the provider
switch network, and when this data reaches
the other side that label is popped off
of this communication.
And the remaining data is sent to the customer edge router.
With MPLS, we have to create an initial configuration that
defines where all of the different sites may be located
and what labels may be used to switch data to those locations.
Other types of wide area networks
could create network connections dynamically,
so that you're only connecting to those sites
when you need to.
This commonly uses MGRE, which is Multipoint Generic Router
Encapsulation, and you'll usually see networks
like a dynamic multipoint VPN, or DMVPN,
used to send data across one of these MGRE networks.
What's nice about these dynamic connections
is they're only created when they're needed,
and they're torn down when you don't have any information
that you need to send.
If you have a break in any of the connections,
the VPN can even rebuild itself to be
able to communicate between all of these different sites.
All of this is considered to be a dynamic mesh because you're
able to send data to whatever site
you would like based on where that data needs to go.
Normally, you would have a main office,
and you would have remote sites that
would connect to the main office over single links.
And if you needed to communicate between remote sites,
that remote site would have to first communicate
to the main office, and then the main office
would have to communicate down to that destination site.
With a dynamic multipoint VPN, you
can have these two sites recognize
that they want to communicate to each other,
they create their own link between the communication,
and when that link is no longer needed, it's disconnected.
If this site needs now to connect
to a different remote site, it can then
create a separate dynamic link to that site,
and of course you can have that site create
a dynamic link as needed.
All of these dynamic multipoint links
mean that you have a more efficient network.
You're only using connectivity when you have to have it,
and if you do need to send information between two
remote sites, you can send that data directly rather than
hopping through a main office.
A newer type of wide area network
is an SD wide area network, or SDWAN.
The SD stands for Software Defined, which
means that our wide area network can be defined however
we would like to lay it out.
This is especially useful if you have cloud-based applications
and you need the network to understand where data needs
to go at any particular time.
We used to have a data center that
was located in one central building,
and we simply connected all of our remote sites
to that one data center.
Now that we have cloud based applications,
we need to communicate to the cloud.
And instead of having to hop through this data center
to be able to access those cloud-based resources,
we can have the wide area network recognize
that we need to communicate directly to those resources
rather than sending all of that data
through one central data center.
Here's our wide area networks before we
had cloud-based services and before we had software
defined wide area networks.
We had our data center.
Inside of our data center were all
of our services, our email servers, our database servers,
and all of our other data.
All of these remote sites would need
to connect to the data center to be able to gain access
to those resources.
With cloud-based services, we've taken our email services,
we've moved them to the cloud.
All of our servers are now at a cloud provider,
and we might have our databases inside yet another cloud
provider.
Instead of having all these remote sites then
communicate to this central data center, and then hop
to all of these cloud-based services,
we could have our wide area network automatically
know where to send the data based on the type of data
that it is.
So if a remote site needs to access
data that's in a cloud database, they
can access that information directly from the cloud.
If another site needs to grab an email message that's
located in a cloud-based email service,
they can communicate directly to that email service instead
of hopping through a central data center.
The determination of how this data is routed
is in the wide area network itself.
That software defined aspect of the SDWAN
determines how data is rooted and sent
based on the type of services that are required.
This makes for a much more efficient network.
This allows us to have instant access
to our cloud-based resources instead
of having to hop through a central point
or build out a separate network to gain access
to those resources.