1
00:00:00,870 --> 00:00:03,000
We spent a lot of time in the last lesson

2
00:00:03,000 --> 00:00:06,120
talking about the different physical and logical topologies.

3
00:00:06,120 --> 00:00:07,710
Now, all of those logical ones

4
00:00:07,710 --> 00:00:10,020
are still going to apply to our wireless networks,

5
00:00:10,020 --> 00:00:12,088
but when we talk about it from a physical perspective,

6
00:00:12,088 --> 00:00:14,490
wireless does add two different modes

7
00:00:14,490 --> 00:00:16,020
that we need to understand.

8
00:00:16,020 --> 00:00:17,490
So when we look at the first one,

9
00:00:17,490 --> 00:00:19,560
this is called infrastructure mode.

10
00:00:19,560 --> 00:00:21,480
Infrastructure mode is the most common type

11
00:00:21,480 --> 00:00:22,650
of wireless network.

12
00:00:22,650 --> 00:00:24,240
In fact, it's probably the one you're using

13
00:00:24,240 --> 00:00:25,740
to watch this video.

14
00:00:25,740 --> 00:00:28,290
If you're sitting at home, you have wireless in your house

15
00:00:28,290 --> 00:00:29,820
and it connects to an outside provider

16
00:00:29,820 --> 00:00:31,770
through your cable or your fiber modem,

17
00:00:31,770 --> 00:00:33,720
this is infrastructure mode.

18
00:00:33,720 --> 00:00:35,370
You have a centrally managed device,

19
00:00:35,370 --> 00:00:36,870
your wireless access point,

20
00:00:36,870 --> 00:00:39,389
and that you've given it a name, probably a password,

21
00:00:39,389 --> 00:00:41,970
and you use that as you would a star topology

22
00:00:41,970 --> 00:00:44,960
in a physical network, but you're doing it wirelessly.

23
00:00:44,960 --> 00:00:47,790
Now, this is going to support wireless security controls

24
00:00:47,790 --> 00:00:49,770
and other benefits that you just don't get

25
00:00:49,770 --> 00:00:53,070
when you go to our second mode, which is known as ad hoc.

26
00:00:53,070 --> 00:00:55,260
Now, ad hoc is decentralized.

27
00:00:55,260 --> 00:00:57,540
It operates like a peer-to-peer network does.

28
00:00:57,540 --> 00:00:59,820
There's no routers, there's no access points.

29
00:00:59,820 --> 00:01:02,700
Instead, I connect my laptop to your laptop,

30
00:01:02,700 --> 00:01:04,860
and we can make those routing decisions on the fly

31
00:01:04,860 --> 00:01:06,510
and make them dynamically.

32
00:01:06,510 --> 00:01:07,920
This can allow people to jump in

33
00:01:07,920 --> 00:01:10,200
and jump out of the network as much as they want.

34
00:01:10,200 --> 00:01:12,360
It's almost like the old school chat rooms we used to have

35
00:01:12,360 --> 00:01:14,220
on AOL or CompuServe, right?

36
00:01:14,220 --> 00:01:16,650
People would come in, they'd talk, and then they'd leave

37
00:01:16,650 --> 00:01:18,900
and they would just come in and out all of the time.

38
00:01:18,900 --> 00:01:20,940
Well, that's how this wireless network would work

39
00:01:20,940 --> 00:01:22,950
when you're dealing with ad hoc mode.

40
00:01:22,950 --> 00:01:24,720
Now, there is a third type that we have,

41
00:01:24,720 --> 00:01:26,550
which is called a wireless mesh,

42
00:01:26,550 --> 00:01:28,200
and you might think, oh, well,

43
00:01:28,200 --> 00:01:30,510
that's just going to be a combination of the other two.

44
00:01:30,510 --> 00:01:32,190
Well, not really.

45
00:01:32,190 --> 00:01:34,620
A wireless mesh is actually completely different.

46
00:01:34,620 --> 00:01:36,510
A wireless mesh is an interconnection

47
00:01:36,510 --> 00:01:39,360
of different types of nodes, devices, and radios

48
00:01:39,360 --> 00:01:41,490
to create this mesh topology.

49
00:01:41,490 --> 00:01:43,200
So if we're going to have different routers

50
00:01:43,200 --> 00:01:46,110
and gateways and clients and servers and radio antennas,

51
00:01:46,110 --> 00:01:47,190
we're going to mesh them all together

52
00:01:47,190 --> 00:01:49,320
and create this unique network.

53
00:01:49,320 --> 00:01:51,000
So we can use different radio frequencies

54
00:01:51,000 --> 00:01:54,000
like Bluetooth and Wi-Fi, and microwave and cellular

55
00:01:54,000 --> 00:01:55,709
and satellite, and all of them can combine

56
00:01:55,709 --> 00:01:58,110
into this single wireless network

57
00:01:58,110 --> 00:02:00,390
so that we can expand our network access.

58
00:02:00,390 --> 00:02:02,490
This gives us redundant and reliable connections

59
00:02:02,490 --> 00:02:05,400
as we move forward, especially in harsh environments.

60
00:02:05,400 --> 00:02:08,070
So where might we use a wireless mesh topology?

61
00:02:08,070 --> 00:02:09,990
Well, after there's a hurricane

62
00:02:09,990 --> 00:02:12,810
or another disaster-related event, people may come in

63
00:02:12,810 --> 00:02:14,970
to do humanitarian assistance in the area,

64
00:02:14,970 --> 00:02:15,803
and when they come,

65
00:02:15,803 --> 00:02:17,160
they're going to bring their networks with them

66
00:02:17,160 --> 00:02:18,579
because they need a way to communicate back

67
00:02:18,579 --> 00:02:20,370
to where they came from.

68
00:02:20,370 --> 00:02:22,140
So some of them will communicate over cellular

69
00:02:22,140 --> 00:02:23,760
if the cellular network still works,

70
00:02:23,760 --> 00:02:26,070
some over wireless that they bring in and set up,

71
00:02:26,070 --> 00:02:28,680
some over satellite, some over microwave,

72
00:02:28,680 --> 00:02:30,210
some over a landline.

73
00:02:30,210 --> 00:02:32,640
But even if you had a landline, it may not be reliable

74
00:02:32,640 --> 00:02:34,260
because there was a disaster there,

75
00:02:34,260 --> 00:02:36,840
and so they might back that up using a wireless signal

76
00:02:36,840 --> 00:02:39,090
or a satellite or a cellular modem.

77
00:02:39,090 --> 00:02:39,990
Now as we have

78
00:02:39,990 --> 00:02:41,641
all these different connections working together,

79
00:02:41,641 --> 00:02:44,190
this gives us our mesh topology.

80
00:02:44,190 --> 00:02:47,280
So maybe we set up a basecamp that has Wi-Fi in it

81
00:02:47,280 --> 00:02:48,570
for everybody to access,

82
00:02:48,570 --> 00:02:50,700
but then we have it connecting to another base camp

83
00:02:50,700 --> 00:02:52,050
over a microwave link,

84
00:02:52,050 --> 00:02:54,060
and then we have that connecting back over satellite

85
00:02:54,060 --> 00:02:55,680
back to their home country.

86
00:02:55,680 --> 00:02:58,500
This is the idea of using this wireless mesh network.

87
00:02:58,500 --> 00:03:00,480
We're combining these two or three or four

88
00:03:00,480 --> 00:03:02,700
different technologies to create a mesh network

89
00:03:02,700 --> 00:03:04,440
that can be used by anyone.

90
00:03:04,440 --> 00:03:07,260
Now, as we keep expanding our networks over a large area

91
00:03:07,260 --> 00:03:09,630
by combining things with microwave and satellite

92
00:03:09,630 --> 00:03:12,240
and cellular, this is going to allow us

93
00:03:12,240 --> 00:03:14,520
to be able to have all the stuff working together well,

94
00:03:14,520 --> 00:03:15,870
because we have wifi,

95
00:03:15,870 --> 00:03:18,390
that can only go maybe a hundred or 200 feet, right?

96
00:03:18,390 --> 00:03:20,788
But a microwave link can go 30 or 40 miles,

97
00:03:20,788 --> 00:03:24,660
and satellite can go hundreds or thousands of miles.

98
00:03:24,660 --> 00:03:26,040
And so this is the idea here.

99
00:03:26,040 --> 00:03:28,849
As we create this mesh, we can keep expanding our access.

100
00:03:28,849 --> 00:03:30,369
As you can see here in the diagram

101
00:03:30,369 --> 00:03:31,860
where I'm going to be using satellite

102
00:03:31,860 --> 00:03:33,450
to go for thousands of miles,

103
00:03:33,450 --> 00:03:35,400
microwaves to go tens of miles,

104
00:03:35,400 --> 00:03:36,990
and then wireless, which goes, you know,

105
00:03:36,990 --> 00:03:39,090
maybe tens of feet or hundreds of feet.

106
00:03:39,090 --> 00:03:40,500
And we can pull all of this together

107
00:03:40,500 --> 00:03:42,270
to create this great, reliable,

108
00:03:42,270 --> 00:03:43,890
redundant network that we can use

109
00:03:43,890 --> 00:03:46,920
during a disaster or humanitarian assistance type mission.

110
00:03:46,920 --> 00:03:48,060
That's the idea.

111
00:03:48,060 --> 00:03:51,300
So as we talk about topology specific to wireless,

112
00:03:51,300 --> 00:03:52,649
I want you to remember the three types,

113
00:03:52,649 --> 00:03:56,133
infrastructure, ad hoc and mesh topology.