[AUDIO LOGO]
So as we mentioned, there are six processes involved
in MPLS traffic engineering.
In this video, we're just going to jump in and take
a look at the details of each of those processes.
So there's really not a lot to say
in the form of introduction.
Let's just go ahead and jump right in and take a look
at those six processes.
So the first process is information distribution.
For this, the attributes are configured differently
for each link.
And these attributes have to be known by the headend that's
actually setting up the tunnel.
This distribution is going to be handled by the IGP
with those extensions that we talked about previously.
Keep in mind, again, the only two supported, of course,
OSPF and ISIS.
Now, if certain things change, such as link state changes,
or the resource class of a link, or even available bandwidth
crosses a certain threshold, this information
will then be flooded through the rest of the network
again by the IGP.
So this process is the information distribution
and is handled by the IGP.
Number two is path selection.
This occurs at the headend LSR.
That's because this is the device that's
responsible for setting up the tunnel.
This headend LSR has to have the knowledge of the topology
and the link resources.
Now, keep in mind, it's learning this from the IGP.
And then the IGP, of course, uses our CSPF
to calculate the tunnel path.
That's really the whole job here,
is to figure out that path.
A couple of restrictions or qualifications here.
It's, of course, not going to consider any excluded links.
We can exclude any links we want from traffic engineering.
It also does not consider links that
don't have enough bandwidth.
There's going to be certain requirements for the tunnel.
And if a path doesn't support that,
then we're not going to use that path for the tunnel.
Then, of course, it creates the explicit path,
which is that sequence of label switch
routers that this traffic is going to go through.
Step three is the actual path setup.
This is, again, as we mentioned, initiated by the headend.
That's the job of the headend LSR.
And RSVP is used to establish the forwarding state,
exchanging the labels, and getting the LSP up and running.
Number four is admission control.
Admission control is simply handling
whether a router actually has the available resources
to handle what has been requested for the tunnel.
When a tunnel requests a certain requirement,
the router has to say, yes, I can handle that, or no,
I can't.
This, again, is part of the job of RSVP.
Number five is our traffic steering.
Once the tunnel is up and running,
we then have to actually get the traffic to go into that tunnel.
Some ways to do this, static routing.
We can, of course, always just tell traffic
to go down a certain interface, that
interface being the tunnel.
We could use policy routing for this,
or we could most commonly use a feature called autoroute.
As I mentioned, traffic steering will
be covered in a separate video coming up here in this skill.
So we'll get to this one shortly.
The sixth process is path maintenance.
And this has actually two separate responsibilities.
The first is path reoptimization.
This is done on a periodic basis.
From time to time, we will check to see
if there's a better path available
for the current tunnel.
If there is a better path, then a new tunnel
will be built before the switchover.
Of course, the reason we're doing it
before the switchover is that way, we don't lose any traffic.
So that's the reoptimization.
Then, of course, there's path restoration,
which is our second responsibility here.
With path restoration, RSVP is going to send a Path Tear
message to the headend.
This will actually trigger a path recalculation
using either a partial calculation
or a complete calculation.
And if possible, a new tunnel will be built.
So this is really a tearing down and a rebuilding of the tunnel.
In this video, we looked at the processes involved
in discovering, building, maintaining, and if needed,
rebuilding our MPLS TE tunnels.
Now it's time to jump into a little bit more detail
on some of the other control plane
and data plane mechanisms involved
in traffic engineering.
And we're going to do that by jumping into RSVP in more
detail in our next video.
Until then, I hope this has been informative for you.
And I'd like to thank you for viewing.