-: We first talked about data flows back 2 2
in IPv4 earlier in this section. 3 3
But they changed a little bit here in IPv6. 4 4
Now, there's still three data flows, 5 5
but one of them has changed. 6 6
We still have unicast, we still have multicast, 7 7
but now we've done away with broadcast 8 8
and we've introduced something called anycast instead. 9 9
Now, unicast works just like it did in IPv4, 10 10
but instead of using IPv4 addresses, 11 11
we're going to use IPv6 addresses. 12 12
Now, in this case, 13 13
let's say my server wants to send a message 14 14
to both PC1 and PC2. 15 15
Well, it's going to have to send out two copies 16 16
of the same message, one intended for each host, 17 17
because it's going from one server to one host 18 18
and then back from one server to the other host. 19 19
Notice the only difference here is their IP addresses. 20 20
We're using ABCD::1 21 21
and all that space in between those two colons 22 22
will be filled up with zeros 23 23
to get us back to 32 hexadecimal digits. 24 24
Next, we have multicast. 25 25
And in multicast, just like IPv4, we use multicast groups. 26 26
The server is going to address the message 27 27
to the multicast group, in this case, FF00::A. 28 28
Remember, anything that starts with FF 29 29
is a multicast address. 30 30
And then it's going to get to the switch. 31 31
And when it gets to the switch, 32 32
it distributes the additional copies 33 33
to each of the recipients 34 34
in the multicast group number based on this number one 35 35
that we're using. 36 36
Data is going to travel from the single source, 37 37
our server, to multiple but specific destination devices. 38 38
The third type of data flow we have is known as anycast. 39 39
And this is the different one from IPv4. 40 40
This is the one that's unique to IPv6 41 41
because we did away with broadcast in IPv4. 42 42
Now, anycast is designed to let one host initiate 43 43
an efficient updating of router tables 44 44
for a group of other hosts. 45 45
IPv6 is able to determine which gateway the host 46 46
is closest to and send the packets to that gateway 47 47
as though it was a unicast communication. 48 48
The gateway is then going to broadcast that 49 49
through the anycast to any other hosts in the group until 50 50
all of the routing tables are updated. 51 51
Now, what does this really look like? 52 52
Well, let's take a look at this diagram on the screen. 53 53
Here we have a server and the router there 54 54
is gone on the left 55 55
is going to send things out through anycast. 56 56
It sends it out to the internet 57 57
and it's going to go to whatever the closest place is 58 58
that has a router. 59 59
Now in this case, it's the router 60 60
that's at the top of the screen here. 61 61
Now, once it gets to that router on top, 62 62
it's then going to go to the DNS server 63 63
and it will reroute down through the routers onto the bottom 64 64
and keep pushing that around, 65 65
but the original router on the left side 66 66
of the screen only had to send out that message once. 67 67
And then from there, 68 68
all of the other routers will figure out the best way 69 69
to update everybody else's tables. 70 70
That's the benefit of using something like anycast, 71 71
as opposed to using another way to update your routers. 72 72
And this becomes very efficient 73 73
and it's one of the benefits of using IPv6.