[AUDIO LOGO]
The next PIM enhancement we want to look at
is Bidir-PIM or Bidirectional PIM.
Now, as we've seen so far through all
of our multicast skills, multicast
is generally a one way tree.
Everything flows from the source to all the receivers.
The problem with that model is what
happens when we have a large number of sources.
Well, that would mean we would have
to have a large number of trees each one routed at a source.
And that doesn't scale very well if we have a lot of sources.
So the idea behind Bidirectional PIM
is we can actually allow traffic to flow
up and down the multicast distribution tree.
Now, in order to do that, we do have
to follow a few guidelines.
So, in this video, let's try to talk about what is Bidir-PIM,
why do we care what's it for, and how does it work.
So let's go ahead and jump in and take a look
at the attributes of Bidir-PIM.
So let's talk about some of those attributes
of Bidirectional PIM or Bidir-PIM.
So as we mentioned during the introduction,
PIM is generally an expanding tree,
or you could say a one-way tree from the source going
to the receivers.
That's what we've seen so far.
But as we mentioned, what if there
are numerous or many sources?
Now I put some examples on here things like video conferencing.
If we think about this, everybody on a video conference
is a source.
They're also a receiver.
So again, these can be sources and receivers.
That's perfectly fine.
Another example could be something like online gaming.
Everybody has to send their information from their game
to everybody else's--
things like player position and things like that.
All of this information needs to be shared.
Now, of course, since we don't support multicast
on the internet at the moment, most of these things,
unless they're internal to a company such as possibly
internal video conferencing, would not be using Bidir-PIM.
Again, certainly not online gaming since the online part
does not support that.
However, I'm just trying to give some examples of things
that could potentially benefit from Bidirectional PIM.
Again, the overall idea is that we
want to allow the traffic to flow
in both directions on the multicast distribution tree.
So not only is traffic flowing down the tree
but traffic is allowed to flow up the tree as well.
Now just based on what you've learned already,
hopefully, this is setting off some alarms in your head
such as, well, how are we even going to do that?
Well, the simple fact is since there are now multiple sources,
the source can no longer be the root of the tree.
OK, well, that means we're not going to have
any more source-based trees.
Well, if there's no more source-based trees,
then what are we going to do?
Well, quite simply all the distribution trees
are now going to be routed on the RP.
So the RP is going to become a central hub
not just for learning source information
but also for the data plane.
The RP will always be in the data
plane in Bidirectional PIM.
All of our entries are going to be star comma G entries.
There are no source trees.
We only use the shared tree.
This is critical to how Bidirectional PIM works.
For loop prevention in this environment
what we're going to do is we're going
to elect a designated forwarder or a DF that's
in charge of forwarding all the traffic
on each individual segment.
That way, there are no loops that
can occur in this environment.
So, in this video, we just jumped in and talked about some
of the attributes of Bidirectional PIM.
The big key takeaways here all traffic
flows through the rendezvous point
that becomes our central hub, not just for information
but also for the data plane and that
means that all of our trees are star comma G trees.
We don't have source trees because, again, there
would have to be way too many of them.
So talking about this is very useful,
but it's also very helpful to jump into the command line
and see Bidirectional PIM in action.
And that's exactly what you and I get to do next.
Till then, I hope this has been informative for you,
and I'd like to thank you for viewing.