1 1 00:00:00,530 --> 00:00:02,580 We first talked about data flows back 2 2 00:00:02,580 --> 00:00:05,060 in IPv4 earlier in this section. 3 3 00:00:05,060 --> 00:00:08,090 But they changed a little bit here in IPv6. 4 4 00:00:08,090 --> 00:00:09,790 Now, there's still three data flows, 5 5 00:00:09,790 --> 00:00:11,450 but one of them has changed. 6 6 00:00:11,450 --> 00:00:14,120 We still have unicast, we still have multicast, 7 7 00:00:14,120 --> 00:00:16,300 but now we've done away with broadcast 8 8 00:00:16,300 --> 00:00:19,320 and we've introduced something called anycast instead. 9 9 00:00:19,320 --> 00:00:22,490 Now, unicast works just like it did in IPv4, 10 10 00:00:22,490 --> 00:00:24,600 but instead of using IPv4 addresses, 11 11 00:00:24,600 --> 00:00:26,990 we're going to use IPv6 addresses. 12 12 00:00:26,990 --> 00:00:27,823 Now, in this case, 13 13 00:00:27,823 --> 00:00:29,470 let's say my server wants to send a message 14 14 00:00:29,470 --> 00:00:31,690 to both PC1 and PC2. 15 15 00:00:31,690 --> 00:00:33,580 Well, it's going to have to send out two copies 16 16 00:00:33,580 --> 00:00:36,360 of the same message, one intended for each host, 17 17 00:00:36,360 --> 00:00:38,680 because it's going from one server to one host 18 18 00:00:38,680 --> 00:00:41,410 and then back from one server to the other host. 19 19 00:00:41,410 --> 00:00:44,250 Notice the only difference here is their IP addresses. 20 20 00:00:44,250 --> 00:00:46,950 We're using ABCD::1 21 21 00:00:46,950 --> 00:00:49,590 and all that space in between those two colons 22 22 00:00:49,590 --> 00:00:50,850 will be filled up with zeros 23 23 00:00:50,850 --> 00:00:53,890 to get us back to 32 hexadecimal digits. 24 24 00:00:53,890 --> 00:00:55,350 Next, we have multicast. 25 25 00:00:55,350 --> 00:00:59,920 And in multicast, just like IPv4, we use multicast groups. 26 26 00:00:59,920 --> 00:01:01,410 The server is going to address the message 27 27 00:01:01,410 --> 00:01:05,920 to the multicast group, in this case, FF00::A. 28 28 00:01:05,920 --> 00:01:08,050 Remember, anything that starts with FF 29 29 00:01:08,050 --> 00:01:09,550 is a multicast address. 30 30 00:01:09,550 --> 00:01:11,350 And then it's going to get to the switch. 31 31 00:01:11,350 --> 00:01:12,750 And when it gets to the switch, 32 32 00:01:12,750 --> 00:01:14,530 it distributes the additional copies 33 33 00:01:14,530 --> 00:01:15,640 to each of the recipients 34 34 00:01:15,640 --> 00:01:18,670 in the multicast group number based on this number one 35 35 00:01:18,670 --> 00:01:20,050 that we're using. 36 36 00:01:20,050 --> 00:01:21,900 Data is going to travel from the single source, 37 37 00:01:21,900 --> 00:01:25,920 our server, to multiple but specific destination devices. 38 38 00:01:25,920 --> 00:01:28,590 The third type of data flow we have is known as anycast. 39 39 00:01:28,590 --> 00:01:31,440 And this is the different one from IPv4. 40 40 00:01:31,440 --> 00:01:33,640 This is the one that's unique to IPv6 41 41 00:01:33,640 --> 00:01:36,660 because we did away with broadcast in IPv4. 42 42 00:01:36,660 --> 00:01:39,340 Now, anycast is designed to let one host initiate 43 43 00:01:39,340 --> 00:01:41,400 an efficient updating of router tables 44 44 00:01:41,400 --> 00:01:43,180 for a group of other hosts. 45 45 00:01:43,180 --> 00:01:46,030 IPv6 is able to determine which gateway the host 46 46 00:01:46,030 --> 00:01:48,930 is closest to and send the packets to that gateway 47 47 00:01:48,930 --> 00:01:51,500 as though it was a unicast communication. 48 48 00:01:51,500 --> 00:01:53,470 The gateway is then going to broadcast that 49 49 00:01:53,470 --> 00:01:56,700 through the anycast to any other hosts in the group until 50 50 00:01:56,700 --> 00:01:58,700 all of the routing tables are updated. 51 51 00:01:58,700 --> 00:02:00,380 Now, what does this really look like? 52 52 00:02:00,380 --> 00:02:02,610 Well, let's take a look at this diagram on the screen. 53 53 00:02:02,610 --> 00:02:04,680 Here we have a server and the router there 54 54 00:02:04,680 --> 00:02:05,513 is gone on the left 55 55 00:02:05,513 --> 00:02:07,740 is going to send things out through anycast. 56 56 00:02:07,740 --> 00:02:09,180 It sends it out to the internet 57 57 00:02:09,180 --> 00:02:11,390 and it's going to go to whatever the closest place is 58 58 00:02:11,390 --> 00:02:12,700 that has a router. 59 59 00:02:12,700 --> 00:02:14,170 Now in this case, it's the router 60 60 00:02:14,170 --> 00:02:16,060 that's at the top of the screen here. 61 61 00:02:16,060 --> 00:02:17,820 Now, once it gets to that router on top, 62 62 00:02:17,820 --> 00:02:19,710 it's then going to go to the DNS server 63 63 00:02:19,710 --> 00:02:22,560 and it will reroute down through the routers onto the bottom 64 64 00:02:22,560 --> 00:02:23,950 and keep pushing that around, 65 65 00:02:23,950 --> 00:02:25,470 but the original router on the left side 66 66 00:02:25,470 --> 00:02:28,510 of the screen only had to send out that message once. 67 67 00:02:28,510 --> 00:02:29,470 And then from there, 68 68 00:02:29,470 --> 00:02:32,010 all of the other routers will figure out the best way 69 69 00:02:32,010 --> 00:02:34,160 to update everybody else's tables. 70 70 00:02:34,160 --> 00:02:36,640 That's the benefit of using something like anycast, 71 71 00:02:36,640 --> 00:02:39,210 as opposed to using another way to update your routers. 72 72 00:02:39,210 --> 00:02:40,970 And this becomes very efficient 73 73 00:02:40,970 --> 00:02:43,373 and it's one of the benefits of using IPv6.