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[AUDIO LOGO]

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So as we mentioned, there
are six processes involved

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in MPLS traffic engineering.

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In this video, we're just
going to jump in and take

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a look at the details of
each of those processes.

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So there's really
not a lot to say

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in the form of introduction.

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Let's just go ahead and jump
right in and take a look

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at those six processes.

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So the first process is
information distribution.

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For this, the attributes
are configured differently

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for each link.

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And these attributes have to
be known by the headend that's

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actually setting up the tunnel.

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This distribution is going
to be handled by the IGP

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with those extensions that
we talked about previously.

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Keep in mind, again, the only
two supported, of course,

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OSPF and ISIS.

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Now, if certain things change,
such as link state changes,

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or the resource class of a link,
or even available bandwidth

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crosses a certain
threshold, this information

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will then be flooded through
the rest of the network

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again by the IGP.

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So this process is the
information distribution

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and is handled by the IGP.

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Number two is path selection.

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This occurs at the headend LSR.

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That's because this
is the device that's

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responsible for
setting up the tunnel.

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This headend LSR has to have
the knowledge of the topology

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and the link resources.

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Now, keep in mind, it's
learning this from the IGP.

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And then the IGP, of
course, uses our CSPF

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to calculate the tunnel path.

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That's really the
whole job here,

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is to figure out that path.

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A couple of restrictions
or qualifications here.

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It's, of course, not going to
consider any excluded links.

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We can exclude any links we
want from traffic engineering.

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It also does not
consider links that

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don't have enough bandwidth.

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There's going to be certain
requirements for the tunnel.

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And if a path
doesn't support that,

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then we're not going to use
that path for the tunnel.

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Then, of course, it
creates the explicit path,

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which is that sequence
of label switch

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routers that this traffic
is going to go through.

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Step three is the
actual path setup.

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This is, again, as we mentioned,
initiated by the headend.

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That's the job of
the headend LSR.

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And RSVP is used to establish
the forwarding state,

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exchanging the labels, and
getting the LSP up and running.

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Number four is
admission control.

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Admission control
is simply handling

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whether a router actually
has the available resources

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to handle what has been
requested for the tunnel.

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When a tunnel requests
a certain requirement,

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the router has to say, yes,
I can handle that, or no,

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I can't.

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This, again, is part
of the job of RSVP.

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Number five is our
traffic steering.

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Once the tunnel
is up and running,

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we then have to actually get the
traffic to go into that tunnel.

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Some ways to do
this, static routing.

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We can, of course,
always just tell traffic

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to go down a certain
interface, that

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interface being the tunnel.

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We could use policy
routing for this,

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or we could most commonly use
a feature called autoroute.

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As I mentioned,
traffic steering will

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be covered in a separate video
coming up here in this skill.

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So we'll get to
this one shortly.

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The sixth process
is path maintenance.

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And this has actually two
separate responsibilities.

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The first is path
reoptimization.

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This is done on
a periodic basis.

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From time to time,
we will check to see

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if there's a better
path available

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for the current tunnel.

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If there is a better
path, then a new tunnel

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will be built before
the switchover.

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Of course, the
reason we're doing it

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before the switchover is that
way, we don't lose any traffic.

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So that's the reoptimization.

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Then, of course, there's
path restoration,

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which is our second
responsibility here.

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With path restoration, RSVP
is going to send a Path Tear

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message to the headend.

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This will actually trigger
a path recalculation

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using either a
partial calculation

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or a complete calculation.

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And if possible, a new
tunnel will be built.

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So this is really a tearing down
and a rebuilding of the tunnel.

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In this video, we looked
at the processes involved

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in discovering, building,
maintaining, and if needed,

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rebuilding our MPLS TE tunnels.

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Now it's time to jump into
a little bit more detail

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on some of the
other control plane

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and data plane
mechanisms involved

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in traffic engineering.

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And we're going to do that
by jumping into RSVP in more

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detail in our next video.

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Until then, I hope this has
been informative for you.

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And I'd like to thank
you for viewing.

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