Anytime we can connect our network from multiple sites to one another directly,
we'll definitely do that.
We will typically take advantage of fiber optics, such as metropolitan area
networks.
Maybe we can even bury our fiber ourselves and extend our local area network,
and we could technically make this a wireless connection called a wireless
local area network.
But inevitably, we're going to have organizations who have sites and locations
that are so far away that we have no option other than to rely on a service
provider here in the middle.
The service provider is going to leverage their own infrastructure and allow us
to connect our different sites, and this is known as a wide area network.
Wide area networking has been in use for many, many decades, and it is
primarily used for us to connect our remote locations.
Now these days, we might be able to take advantage of internet circuits and VPN
s, but wide area networks not only connect our remote sites, they are known to
be extremely reliable.
That is the purpose of taking advantage of wide area networking.
And so when we look at different topologies that we typically leverage when we
're using wide area networks, we have a lot of different options that primarily
revolve around two categories point to point, as well as point to multi point.
So a point to point technology would, for example, be a T1s and our E1s or T3s
and our E3s, and it's going to allow me to have a router at one location, have
a direct connection to a router at another location.
So at this point, I'm going to be responsible for scaling this out to many
locations. If I have a lot of remote sites, then I'm going to need my devices
at each one of these sites to connect individually back to this maybe
headquarters router.
And so the more remotes we have, the less point to point connections make sense
. Now certainly as I said in the intro video, if we have smaller architectures,
maybe a handful of sites or maybe up to a dozen or so sites, then we can
leverage traditional wide area networking, we can leverage point to point
networks, but as we can tell, some of these things just don't scale out very
well to hundreds and potentially thousands of different remote sites. And so
instead, we might look at a point to multi point solution.
And there's several of these, for example, we've got VPLS as one option, we've
got Metro Ethernet. And certainly we have the option of using MPLS.
The idea here is that the service provider is going to form some form of
network. Maybe this is a layer two network. Maybe it's a layer three network
depending on the technology that we choose.
But the idea here is rather than having a bunch of point to point connections
with my headquarters, I can now attach my headquarters to this networking
domain. And then I can have all these remote sites also participate in the same
network.
What this allows is for me to not only share connections out from the
headquarters to all of these other locations, but these locations can even
communicate with one another if we choose to allow for that level of
communication.
So we're no longer talking about just single point to point connections. We're
talking about a shared network on which we can potentially leverage broadcasts.
And if we're running layer two, which makes it so we can easily run our own
routing protocols, or if it's a layer three network like with MPLS, then we
would share routes with the MPLS service provider.
And either way, we're creating a larger domain for us to form networking with
one that scales out a whole lot better.
Now, a big problem as we scale out our wide area networks is going to come to
the idea of redundancy.
Because redundancy is going to require multiple devices, potentially at
critical sites, we might not want to routers at every single remote location,
but we might want them at headquarters and backup headquarters types of
locations.
And certainly here's the big one is redundant circuits, which typically is
going to mean that we're talking about redundant service providers.
We could use multiple circuits from the same service provider, but that in
theory leaves us with a single point of failure potential.
So we would probably want to look at multiple service providers when we're
looking at critical services remaining up.
When we start talking about this level of network and topology build out, we're
introducing a whole lot of complexity.
And furthermore, we're adding in a whole lot of choices that we're going to
have to make that are not really easy.
There's no simple answer to some of the choices.
For example, let's say that I've got my headquarters location.
I'm going to deploy my two different routers, but I want to make sure that I
have redundancy with the service providers.
So I have service provider A here, and I have service provider B down here.
So if one goes down, the other one will pick up the slack and vice versa.
But here's the question, what are these service providers?
What type of service are they offering?
Because if I'm looking at something like MPLS or VPLS or any of these other
technologies, this is very, very expensive, although it is reliable, which is
one of the key tenets of wide area networks.
But we could also take a cheaper approach and do a VPN over the internet.
And if so, that's going to be again much cheaper, but the reliability is a
whole lot less.
Unreliable per se, but we can't necessarily rely on it every single day, giving
us the performance and the latency and all of the requirements that we have,
which is especially relevant with voiceover IP.
So now we look back at our topology, and we are immediately stuck with a really
hard decision.
One of these circuits should absolutely be MPLS, potentially in this scenario,
at least because we care about the reliability.
But should this backup service provider be MPLS, or should it be the internet?
Do we want to spend a whole lot of money maintaining this backup service
provider, especially as we scale it out, to all kinds of sites at our remote
locations?
Or do we want to go cheaper, but if the internet is what we choose, and our MP
LS provider goes down, what will we do with voiceover IP traffic?
These are some of the hard decisions that we have to make.
So either way, where you can maybe get redundant connections to maybe
individual service providers, usually we'll just do something like this, where
we split the redundant connections between two devices, like our routers that
we have drawn out over here.
But now we have to think about how we're going to do this with the remotes,
because the remote sites, now, maybe some of them are critical.
Maybe some of them aren't. So maybe this is a critical location down here, and
so we want to make sure that it's tied into both service providers.
Maybe this one is in the same boat, but these up here, they are just going to
rely on one service provider because we don't necessarily need redundancy at
these locations.
Maybe it's just a few users, and if they go down from a wide area networking
perspective, it's not going to drastically impact my organization.
So this is another set of decision points that we have to make is how do we
connect our remotes into a redundant topology like this?
But even just with four remotes in a headquarters site, look at the complexity
that we've just created.
And yeah, from a topology perspective, maybe it's a little bit complex, but
specifically, we're talking about the routing complexity.
This is going to be a little bit difficult for a couple of reasons. First of
all, we have to make sure that we have proper failover in place.
We have to make sure that we are routing correctly for the sake of efficiency.
But now look at this as well.
Where am I going to be able to deploy routing protocols like EIGRP and OSPF and
possibly BGP in the right situation?
Where do these protocols go? With MPLS, I'm going to have to form routing adjac
encies.
Usually we use OSPF or BGP, depending on the service provider for this, and
that is certainly one option.
But if my service provider B here is the internet, well, now I'm going to have
to run something like the MVPN, which just adds more complexity.
And I might not be able to make these two environments work very well together.
Because the MVPN will run something like EIGRP, and this is going to be
internal routes, meaning that they are going to be favored.
Versus the service provider A being something like MPLS, which is shared
routing, well, now this is going to be maybe OSPF external routes.
And even if I run OSPF over DMBPN here, it's still going to be internal, and
that's going to complicate things.
Because it's supposed to be my backup service provider, and yet it might be
preferred, strictly speaking, from a routing perspective.
Furthermore, I have to worry about where VoiceOver IP is going to go.
Do I want to make sure that VoiceOver IP goes one way and bulk internet traffic
goes another way?
And so we're going to have to look at source based or otherwise just policy
based routing.
As traffic comes into the wide area networking space, we're going to need to
worry about redistribution of routes, and potentially even manipulating the
administrative distance or the metrics that are used in order to figure out
which path is best.
This is a massive part of this conversation. We are developing very large, very
complex wide area networks, and again, we have to make decisions where it's not
always going to be clear what is the right solution.
And these aren't even all of the challenges without diving into details. We're
going to have problems with security.
I'm sharing routes with my service provider here. I am sending traffic into a
shared space, regardless of which vendor this is.
How is security being addressed with wide area networking? It isn't natively
encrypted. What about visibility?
How can I make sure that the traffic that I'm sending into the wide area
network is choosing the path that I think it's going to be choosing, and then
manageability as well?
This is a major concern. How do I manage all these devices? Am I still using
CLI to log in to all of these individual devices and try to manage the domain
myself?
I need to make sure that I can wrap my arms around this topology, and not just
in a way where I as the primary admin have full control over all of this,
because I might leave the company one day or whoever that individual is.
So how do I as an organization make sure that multiple managers can log in and
make changes? Chances are individual CLI configurations isn't the best way to
go there.
So we have a lot of different challenges, not just what we just ended on here,
but naturally adding in redundancy, adding in routing complexity, and let's
keep in mind that cost is a big one as well.
We want to reduce the cost if possible so that we can make proper decisions
around the wide area network providers and technologies that we're choosing in
order to maximize the benefits while minimizing the monthly cost that I have to
spend on all of these circuits.