We first talked about data flows back in IPv4
earlier in this section,
but they changed a little bit here in IPv6.
Now there's still three data flows,
but one of them has changed.
We still have unicast,
we still have multicast,
but now we've done away with broadcast
and we've introduced something called Anycast instead.
Now, unicast works just like it did in IPv4,
but instead of using IPv4 addresses,
we're going to use IPv6 addresses.
Now in this case, let's say my server wants
to send a message to both PC one and PC two.
Well, it's going to have to send out two copies
of the same message, one intended for each host
because it's going from one server to one host,
and back from one server to the other host.
Notice the only difference here is their IP addresses.
We're using A, B, C, D, colon colon one,
and all this space in between those two colons
will be filled up with zeros
to get us back to 32 hexa decimal digits.
Next we have multicast.
And in multicast, just like IPv4,
we use multicast groups.
The server's going to address the message
to the multicast group.
In this case FF zero zero colon colon A.
Remember, anything that starts
with FF is a multicast address,
and then it's going to get to the switch.
And when it gets to the switch,
it distributes the additional copies to each
of the recipients in the multicast group number
based on this number one that we're using.
Data is going to travel from a single source, our server
to multiple but specific destination devices.
The third type of data flow we have is known as anycast.
And this is the different one from IPv4.
This is the one that's unique to IPv6
because we did away with broadcast in IPv4.
Now any cast is designed
to let one host initiate an efficient updating
of router tables for a group of other hosts.
IPV six is able to determine which gateway the host
is closest to and send the packets to that gateway
as though it was a unicast communication.
The gateway is then going to broadcast that through the anycast
to any other host in the group until all
of the routing tables are updated.
Now what does this really look like?
Well, let's take a look at this diagram on the screen.
Here we have a server, and the router there is gone left,
is going to send things out through anycast,
it sends it out to the internet, and it's going to go
to whatever the closest place is that has a router.
Now, in this case, it's the router
that's at the top of the screen here.
Now once it gets to that router on top, it's then going to go
to the DNS server and it'll reroute down
through the routers onto the bottom
and keep pushing that around,
but the original router on the left side
of the screen only had to send out that message once,
and then from there,
all of the other routers will figure out the best way
to update everybody else's tables.
That's the benefit of using something like anycast
as opposed to using another way to update your routers.
And this becomes very efficient
and it's one of the benefits of using IPv6.