WEBVTT 00:00:01.090 --> 00:00:03.190 Let's take a look at computer networking. 00:00:03.850 --> 00:00:07.390 The definition of a network is two or more devices 00:00:07.390 --> 00:00:09.340 that can communicate with each other. 00:00:09.750 --> 00:00:12.440 So the first networks were really quite simple. 00:00:12.670 --> 00:00:17.320 We put a crossover cable between two different systems and 00:00:17.320 --> 00:00:19.770 so they could communicate and share data. 00:00:20.210 --> 00:00:24.370 That expanded later to the idea of a hub where we had 00:00:24.370 --> 00:00:28.210 many devices that could all share data, and for example, 00:00:28.250 --> 00:00:33.310 now as we see in this diagram, three computers could share the same printer. 00:00:33.760 --> 00:00:39.150 The problem with a hub was that all the traffic going from one device 00:00:39.150 --> 00:00:42.340 to another was also shared with all of the others. 00:00:43.560 --> 00:00:47.690 So along came the idea of a switch, and in fact, 00:00:47.690 --> 00:00:52.510 joining switches together so we could have different local area networks, 00:00:52.520 --> 00:00:56.260 each attached to their own switch, but then joined together, 00:00:56.260 --> 00:00:59.570 and maybe we could call it a tree type of assembly. 00:01:00.100 --> 00:01:04.099 The advantage of a switch is that traffic going from one device to 00:01:04.099 --> 00:01:09.280 another only went to that destination device and wasn't shared with 00:01:09.290 --> 00:01:12.090 everybody else on the network as well. 00:01:13.600 --> 00:01:15.730 When we look at network transmission, 00:01:16.200 --> 00:01:19.870 the first network transmissions really were wired using 00:01:19.870 --> 00:01:23.470 copper to join two devices together, 00:01:23.470 --> 00:01:27.100 but then came the idea of using coaxial cable, 00:01:27.400 --> 00:01:31.620 a little higher bandwidth or more traffic you could put down. 00:01:31.620 --> 00:01:37.080 The idea of fiber greatly increased the speeds of many of our networks, 00:01:37.080 --> 00:01:41.990 but also we saw the development and evolution of different types of wireless. 00:01:42.500 --> 00:01:46.510 We had wireless access points and wireless fidelity, 00:01:46.510 --> 00:01:52.060 the idea of Wi‑Fi being that now we had a wireless access point 00:01:52.170 --> 00:01:55.750 that provided access to many devices in that area. 00:01:56.830 --> 00:02:02.070 Satellite and microwave were two of the types of wireless 00:02:02.070 --> 00:02:04.700 communications that required line of sight. 00:02:05.350 --> 00:02:08.699 The device that was going to communicate with a satellite, 00:02:08.699 --> 00:02:11.310 or between two microwave systems, 00:02:11.310 --> 00:02:15.650 had to be able to see that other destination point. 00:02:15.950 --> 00:02:19.120 We couldn't have trees or other things in the way. 00:02:20.220 --> 00:02:22.790 We also had the development of infrared, 00:02:22.790 --> 00:02:27.180 used a lot in conferences and so on where we could actually 00:02:27.180 --> 00:02:30.310 transmit data using infrared signals. 00:02:31.120 --> 00:02:34.530 So we have had many different types of networks. 00:02:34.740 --> 00:02:39.400 Some networks, by their very nature, are more secure than others. 00:02:39.420 --> 00:02:44.860 For example, fiber tends to be a rather secure type of network communications, 00:02:44.860 --> 00:02:47.200 whereas something like satellite, 00:02:47.440 --> 00:02:50.910 the traffic can be picked up by many thousands of devices 00:02:50.920 --> 00:02:53.930 over hundreds of square miles or kilometers. 00:02:55.350 --> 00:02:57.920 When we look at network types, we, of course, 00:02:57.920 --> 00:03:02.450 have local area networks, which are networks within one fixed, 00:03:02.450 --> 00:03:04.840 usually small geographic area. 00:03:05.640 --> 00:03:08.860 Then we had wide area networks where we could join 00:03:08.860 --> 00:03:13.260 different local area networks together, often a distance apart, 00:03:13.540 --> 00:03:18.170 usually using some type of leased line from a telecommunications carrier. 00:03:18.960 --> 00:03:20.930 We had personal area networks. 00:03:20.940 --> 00:03:23.340 Many of us are very familiar with this. 00:03:23.580 --> 00:03:30.430 We have maybe a set of AirPods in our ear talking to the phone on our hip, 00:03:30.620 --> 00:03:33.190 and those are communicating via Bluetooth, 00:03:33.190 --> 00:03:36.630 and we would call that a personal area network. 00:03:37.810 --> 00:03:41.040 We've also seen the development of DARPANET and, 00:03:41.040 --> 00:03:45.080 of course, the internet as a result of that, 00:03:45.080 --> 00:03:47.140 a combination of many, 00:03:47.140 --> 00:03:51.970 many networks joined together into an international network, 00:03:51.980 --> 00:03:54.290 which is why we call it internet. 00:03:54.290 --> 00:03:56.400 The idea, of course, 00:03:56.410 --> 00:04:01.920 of the internet is it that allows us to communicate now all over the world, 00:04:01.920 --> 00:04:05.380 and it's a network that's highly resilient to failure 00:04:05.470 --> 00:04:08.610 because if traffic has a problem in one area, 00:04:08.610 --> 00:04:12.530 it can route over a different direction or a different path. 00:04:14.040 --> 00:04:15.900 The Key Points Review. 00:04:15.900 --> 00:04:19.329 Networks can be very small, two devices, 00:04:19.329 --> 00:04:22.089 and very simple, but of course, 00:04:22.100 --> 00:04:27.480 we know that they can also become very large and complex and international.