WEBVTT 0:00:05.260000 --> 0:00:09.120000 So I think a very good place to start out our discussion of ethernet, 0:00:09.120000 --> 0:00:13.240000 especially if you have no idea what ethernet is, is to talk a little bit 0:00:13.240000 --> 0:00:17.320000 about its an overview of it and its history, how it came to be and how 0:00:17.320000 --> 0:00:18.600000 it was developed. 0:00:18.600000 --> 0:00:22.700000 So let's say that you've never heard of this term ethernet before. 0:00:22.700000 --> 0:00:25.020000 This is the first time you've never read anything. 0:00:25.020000 --> 0:00:26.720000 You've never watched any videos on it. 0:00:26.720000 --> 0:00:29.840000 This is the first time you're hearing that term and you're wondering what 0:00:29.840000 --> 0:00:33.640000 is ethernet and why should I care? 0:00:33.640000 --> 0:00:35.520000 Hence the title of this video series. 0:00:35.520000 --> 0:00:38.760000 Well, think about the concept of networking. 0:00:38.760000 --> 0:00:42.760000 Now imagine that you could actually see with your eyes what was going 0:00:42.760000 --> 0:00:46.760000 on inside your laptop when things are being networked. 0:00:46.760000 --> 0:00:52.040000 So at a very high level, your processor, your CPU and your laptop, and 0:00:52.040000 --> 0:00:59.160000 I'm just going to use wired ethernet. 0:00:59.160000 --> 0:01:02.100000 The processor in your laptop is running basically two different kinds 0:01:02.100000 --> 0:01:03.500000 of applications. 0:01:03.500000 --> 0:01:08.080000 You've got those applications which are non-networked applications. 0:01:08.080000 --> 0:01:14.020000 For example, notepad if you're in Windows or Microsoft Excel, right? 0:01:14.020000 --> 0:01:16.460000 Or maybe a Windows photo viewer. 0:01:16.460000 --> 0:01:19.800000 These are all things that are self -contained within your laptop. 0:01:19.800000 --> 0:01:22.220000 They have no idea there's an outside world. 0:01:22.220000 --> 0:01:26.600000 There's nothing built into those applications to fetch data or to push 0:01:26.600000 --> 0:01:30.400000 data to or from remote locations. 0:01:30.400000 --> 0:01:33.040000 That's a non-networked application. 0:01:33.040000 --> 0:01:37.640000 Then you have networked applications such as Google Chrome or Microsoft 0:01:37.640000 --> 0:01:40.100000 Outlook or something like that. 0:01:40.100000 --> 0:01:43.500000 These are applications that within the program for that application, there's 0:01:43.500000 --> 0:01:48.720000 a component of the program that says, okay, to get this data, it's not 0:01:48.720000 --> 0:01:50.220000 here in my laptop. 0:01:50.220000 --> 0:01:50.980000 I have to go elsewhere. 0:01:50.980000 --> 0:01:54.880000 I have to go out to the network to fetch that data or I have to push this 0:01:54.880000 --> 0:01:56.680000 data out of the network. 0:01:56.680000 --> 0:02:00.500000 So when you're using that type of an application, you're going to do something. 0:02:00.500000 --> 0:02:01.640000 You're going to click some button. 0:02:01.640000 --> 0:02:05.740000 You're going to select some drop-down menu which is going to invoke that 0:02:05.740000 --> 0:02:09.280000 networking portion of that application. 0:02:09.280000 --> 0:02:11.920000 And so then that application is going to talk to your CPU and it's going 0:02:11.920000 --> 0:02:14.900000 to say, hey, CPU, I need this data. 0:02:14.900000 --> 0:02:17.100000 It's not located on me. 0:02:17.100000 --> 0:02:18.260000 Here's where it is. 0:02:18.260000 --> 0:02:23.500000 It will probably provide like an IP address or a domain name or something 0:02:23.500000 --> 0:02:25.960000 like that to get that data. 0:02:25.960000 --> 0:02:30.500000 So at that level, networking is taking place where there's some interaction 0:02:30.500000 --> 0:02:33.040000 between the application, the CPU. 0:02:33.040000 --> 0:02:39.220000 The CPU then has to invoke another application like TCP or UDP, which 0:02:39.220000 --> 0:02:42.020000 will then spin off another application of IP. 0:02:42.020000 --> 0:02:48.840000 So it can take this data, format it inside of a TCP segment, put that 0:02:48.840000 --> 0:02:50.420000 inside of an IP packet. 0:02:50.420000 --> 0:02:53.820000 So now all that has happened inside of your laptop. 0:02:53.820000 --> 0:02:56.480000 Nothing has actually left your laptop yet. 0:02:56.480000 --> 0:03:02.940000 Now, to actually get onto the network, to get this data out of your laptop, 0:03:02.940000 --> 0:03:04.780000 two things have to occur. 0:03:04.780000 --> 0:03:09.520000 Number one, your laptop has to know, how do I physically connect to the 0:03:09.520000 --> 0:03:13.280000 outside world? With your laptop, you basically have three methods. 0:03:13.280000 --> 0:03:15.880000 You've got some sort of wired cable and that's what we're going to be 0:03:15.880000 --> 0:03:20.160000 focusing on is wired ethernet, some sort of actual cable stuck in there. 0:03:20.160000 --> 0:03:24.480000 You could be doing Wi-Fi or you could potentially even be doing Bluetooth. 0:03:24.480000 --> 0:03:27.140000 And there's probably one or two other options as well, but those are like 0:03:27.140000 --> 0:03:30.200000 the top three most popular ones. 0:03:30.200000 --> 0:03:34.860000 So in the case of ethernet, ethernet is a protocol where your laptop says, 0:03:34.860000 --> 0:03:42.900000 okay, in case somebody who needs it, I need to go out this cable. 0:03:42.900000 --> 0:03:46.080000 I know I'm connected to this cable, this cable is connected to this physical 0:03:46.080000 --> 0:03:48.260000 adapter that's connected to me. 0:03:48.260000 --> 0:03:52.500000 All right. So ethernet involves some sort of physical layer. 0:03:52.500000 --> 0:03:57.280000 In other words, something physical you can touch and see to connect to 0:03:57.280000 --> 0:03:59.640000 the network, which is your cable. 0:03:59.640000 --> 0:04:04.840000 But in addition to that, any networking protocol that is in charge of 0:04:04.840000 --> 0:04:10.560000 pushing that data out, whether it be via a cable or Wi-Fi or whatever, 0:04:10.560000 --> 0:04:14.180000 the next thing it has to know is not only physically what it's going to 0:04:14.180000 --> 0:04:19.320000 use and where that physical device resides on the laptop or the tablet, 0:04:19.320000 --> 0:04:24.140000 it also has to know what are the rules for using that device. 0:04:24.140000 --> 0:04:28.820000 In other words, things like, okay, this particular cable, what are the 0:04:28.820000 --> 0:04:30.040000 rules for me using it? 0:04:30.040000 --> 0:04:32.600000 Can I send data whenever I want? 0:04:32.600000 --> 0:04:35.060000 Or is there some rule that says, okay, I have to wait a certain amount 0:04:35.060000 --> 0:04:39.340000 of time. Make sure the cable's free, nobody else is using it. 0:04:39.340000 --> 0:04:41.000000 And then I can send my data. 0:04:41.000000 --> 0:04:44.100000 Other rules about, okay, once I start setting my bits, can I just do so 0:04:44.100000 --> 0:04:47.260000 in a continuous stream and just go and go and go and go for the next 30 0:04:47.260000 --> 0:04:49.320000 minutes until I'm finally done? 0:04:49.320000 --> 0:04:52.720000 Or is there a rule that says every once in a while I have to stop so that 0:04:52.720000 --> 0:04:56.200000 somebody else can use that networking cable in addition to me? 0:04:56.200000 --> 0:04:57.820000 And all sorts of other rules as well. 0:04:57.820000 --> 0:05:00.740000 So that's also another component of ethernet. 0:05:00.740000 --> 0:05:04.040000 Ethernet, if you actually read the specification, which is hundreds of 0:05:04.040000 --> 0:05:08.100000 pages long, not only would you read all sorts of things about cabling, 0:05:08.100000 --> 0:05:11.860000 like, you know, how thick the wire should be, how long the wire can be 0:05:11.860000 --> 0:05:16.520000 from an electricity perspective, how do we manipulate electricity to represent 0:05:16.520000 --> 0:05:22.020000 a one or a zero, how long do we make those electrical changes on the cable? 0:05:22.020000 --> 0:05:25.440000 That's all physical layer stuff, low level stuff, but that same document 0:05:25.440000 --> 0:05:30.120000 would also provide you these rules about when can you use the cable, when 0:05:30.120000 --> 0:05:33.480000 must you stop, how do you know when somebody else is using it and a whole 0:05:33.480000 --> 0:05:35.000000 bunch of other stuff? 0:05:35.000000 --> 0:05:37.940000 So all of that is built into ethernet. 0:05:37.940000 --> 0:05:39.180000 So that's what we're going to talk about. 0:05:39.180000 --> 0:05:41.420000 Now there's other protocols that do that as well. 0:05:41.420000 --> 0:05:44.840000 For example, when ethernet came out, there was a competing technology 0:05:44.840000 --> 0:05:46.960000 at the time called token ring. 0:05:46.960000 --> 0:05:50.160000 Token ring also used a cable. 0:05:50.160000 --> 0:05:53.820000 Token ring also had its own special adapter, but the rules for accessing 0:05:53.820000 --> 0:05:57.620000 that cable, the rules for putting data on and off of it were very different 0:05:57.620000 --> 0:06:01.720000 than ethernet. So ethernet and token ring are both examples of protocols 0:06:01.720000 --> 0:06:06.140000 that are designed to say, how do I actually get to the outside world? 0:06:06.140000 --> 0:06:13.680000 What's the physical media and how do I access that physical media? 0:06:13.680000 --> 0:06:19.240000 So ethernet was originally developed by Xerox in 1973, and then they patented 0:06:19.240000 --> 0:06:23.420000 it in 1977. I'm going to go into a little bit more details of that in 0:06:23.420000 --> 0:06:28.680000 just a moment. I'm going to go to the bottom for quite a while. 0:06:28.680000 --> 0:06:31.740000 The first IEEE standard was published in 1985. 0:06:31.740000 --> 0:06:35.520000 So you can see there was a 12-year period from the time it was originally 0:06:35.520000 --> 0:06:39.960000 developed until the first IEEE standard was derived, and that was the 0:06:39.960000 --> 0:06:46.380000 IEEE 802.3 standard. 0:06:46.380000 --> 0:06:49.240000 And when people are talking about ethernet, when they're throwing that 0:06:49.240000 --> 0:06:58.580000 term around, you know, the original flavor, and we'll look at that, and 0:06:58.580000 --> 0:07:03.440000 then there's the IEEE standard, 802 .3, and they're very, very similar, 0:07:03.440000 --> 0:07:06.560000 but there are a couple of unique differences that may be relevant when 0:07:06.560000 --> 0:07:09.860000 it comes to troubleshooting things, and so you really should know what 0:07:09.860000 --> 0:07:12.360000 type of ethernet somebody is talking about. 0:07:12.360000 --> 0:07:18.500000 And various cabling types and speeds are supported. 0:07:18.500000 --> 0:07:22.340000 Back when it was first developed in 1973, there was only one kind of cable 0:07:22.340000 --> 0:07:25.240000 that it used, and only one kind of speed. 0:07:25.240000 --> 0:07:30.280000 But we're going to see here how it has definitely evolved over time. 0:07:30.280000 --> 0:07:35.720000 Okay, I found this fact a little interesting when I did my research, and 0:07:35.720000 --> 0:07:38.820000 I just thought I'd throw it in here for those of you who are like me and 0:07:38.820000 --> 0:07:41.320000 find this kind of stuff fascinating. 0:07:41.320000 --> 0:07:45.160000 So many of these protocols, these networking protocols and stuff we use 0:07:45.160000 --> 0:07:50.440000 today were created because somebody saw something older, and they thought, 0:07:50.440000 --> 0:07:51.460000 I can do better than that. 0:07:51.460000 --> 0:07:55.580000 I can use some of the same concepts in that older protocol and tweak them, 0:07:55.580000 --> 0:07:58.620000 revise them, and make it better and make my own thing. 0:07:58.620000 --> 0:08:00.080000 And that's the same way with ethernet. 0:08:00.080000 --> 0:08:08.440000 So actually, there was a network before ethernet called the Aloha Net, 0:08:08.440000 --> 0:08:12.620000 and Aloha. Yes, Hawaii was developed at the University of Hawaii, and 0:08:12.620000 --> 0:08:15.580000 it became operational in 1971. 0:08:15.580000 --> 0:08:18.480000 And the purpose of this network, it was a radio network. 0:08:18.480000 --> 0:08:23.420000 It was like early Wi-Fi before Wi-Fi even came out, a radio network for 0:08:23.420000 --> 0:08:26.240000 communicating among the Hawaiian islands. 0:08:26.240000 --> 0:08:29.440000 Now if you're kind of like me, Aloha is actually an acronym, believe it 0:08:29.440000 --> 0:08:34.800000 or not, it stood for the Additive Links Online Hawaii Area. 0:08:34.800000 --> 0:08:38.980000 That's right, Additive Links Online Hawaii Area Network. 0:08:38.980000 --> 0:08:43.500000 Kind of cool. And it was a very simple wireless mechanism. 0:08:43.500000 --> 0:08:48.780000 Basically it was, okay, any device connected to the Aloha network could 0:08:48.780000 --> 0:08:50.780000 transmit at any time. 0:08:50.780000 --> 0:08:55.340000 If it had something to send, it could transmit over this wireless Aloha 0:08:55.340000 --> 0:08:59.700000 network. And the idea was once you're done transmitting, you need to get 0:08:59.700000 --> 0:09:01.280000 an acknowledgment back. 0:09:01.280000 --> 0:09:04.060000 That's how you knew that your transmission was successful. 0:09:04.060000 --> 0:09:08.360000 But because any device could transmit at any time, there was nothing preventing 0:09:08.360000 --> 0:09:11.980000 multiple devices from transmitting at the same time. 0:09:11.980000 --> 0:09:15.500000 And then their wireless signals would collide with each other. 0:09:15.500000 --> 0:09:19.940000 And then that electromagnetic, that RF, that radio frequency would become 0:09:19.940000 --> 0:09:24.200000 distorted. And they'll see signals would be meaningless. 0:09:24.200000 --> 0:09:25.600000 That was called a collision. 0:09:25.600000 --> 0:09:28.840000 So in the Aloha network, basically you just transmitted. 0:09:28.840000 --> 0:09:32.100000 If there was a collision, you wouldn't get an acknowledgment. 0:09:32.100000 --> 0:09:34.980000 That's how you knew that there had been a collision. 0:09:34.980000 --> 0:09:37.700000 So then you would just retransmit because you assumed that there was an 0:09:37.700000 --> 0:09:40.480000 acknowledgment, that there was no acknowledgment. 0:09:40.480000 --> 0:09:45.180000 So real simple network. 0:09:45.180000 --> 0:09:49.140000 So let's bring in Dr. 0:09:49.140000 --> 0:09:54.400000 Robert Metcalf. So in 1973 we had this brilliant guy called Dr. 0:09:54.400000 --> 0:09:57.600000 Robert Metcalf. I believe he was a physicist at the time. 0:09:57.600000 --> 0:10:00.000000 And he was working at Xerox. 0:10:00.000000 --> 0:10:03.800000 He was actually working at the Palo Alto Research Center in Palo Alto, 0:10:03.800000 --> 0:10:09.480000 California. And he was thinking to himself, he said, you know what? 0:10:09.480000 --> 0:10:12.320000 We at Xerox have created some pretty cool things. 0:10:12.320000 --> 0:10:14.980000 We've created like the first personal computer. 0:10:14.980000 --> 0:10:16.900000 There it is, the Xerox Alto. 0:10:16.900000 --> 0:10:18.140000 That's a picture of it right there. 0:10:18.140000 --> 0:10:20.760000 The Xerox will make this a little bit bigger so you can see it. 0:10:20.760000 --> 0:10:24.060000 They had also developed some of the first laser printers at that time. 0:10:24.060000 --> 0:10:25.220000 And he said, you know what? 0:10:25.220000 --> 0:10:30.260000 It would be nice if a whole bunch of these Xerox Alto's could somehow 0:10:30.260000 --> 0:10:34.520000 be networked together to make use of this laser printer so that every 0:10:34.520000 --> 0:10:37.720000 person doesn't need their own individual laser printer. 0:10:37.720000 --> 0:10:41.000000 It'd be nice if the whole floor or the whole company could all share that 0:10:41.000000 --> 0:10:45.920000 resource. And so he started thinking about that. 0:10:45.920000 --> 0:10:49.380000 And he thought about the Aloha Network. 0:10:49.380000 --> 0:10:50.740000 And he said, you know what? 0:10:50.740000 --> 0:10:53.900000 The Aloha Network, I could use that. 0:10:53.900000 --> 0:10:57.620000 Why don't I just make that into a network that uses cables instead of 0:10:57.620000 --> 0:11:02.100000 wireless? And I'm going to make it a little bit better so there's less 0:11:02.100000 --> 0:11:05.480000 chances of collisions so we can speed it up, make it a little bit more 0:11:05.480000 --> 0:11:10.620000 efficient. And what he came up with was Ethernet. 0:11:10.620000 --> 0:11:15.780000 So Xerox Park, that stands for the Palo Alto Research Center. 0:11:15.780000 --> 0:11:21.580000 And so in his design, his Ethernet design, his design used cables, whereas 0:11:21.580000 --> 0:11:24.280000 the Aloha Network was wireless between islands. 0:11:24.280000 --> 0:11:26.960000 It was designed to interconnect LAN systems. 0:11:26.960000 --> 0:11:30.040000 It was based on those concepts in the Aloha Network. 0:11:30.040000 --> 0:11:32.500000 But here was one of the key differences. 0:11:32.500000 --> 0:11:37.260000 He said, the main problem with the Aloha Network is that any device can 0:11:37.260000 --> 0:11:39.480000 transmit whenever it wants. 0:11:39.480000 --> 0:11:43.640000 And the way it knows if it was successful or not was if it gets an acknowledgment 0:11:43.640000 --> 0:11:47.440000 back. If it doesn't get acknowledgment, try again. 0:11:47.440000 --> 0:11:51.680000 And he thought, what if I created some way of arbitrating access? 0:11:51.680000 --> 0:11:56.480000 In other words, well, let's try to make a little bit more fair, where 0:11:56.480000 --> 0:12:00.600000 devices don't step on each other's toes, and there's more of a chance 0:12:00.600000 --> 0:12:04.420000 of when you're talking, nobody else is talking, when you're talking, everybody 0:12:04.420000 --> 0:12:09.060000 knows that they need to listen, and less chance of the collisions happening. 0:12:09.060000 --> 0:12:14.600000 And so he, along with somebody else, invented the CSMA CD algorithm that 0:12:14.600000 --> 0:12:18.920000 we'll be talking about, which significantly speeded up the process of 0:12:18.920000 --> 0:12:21.960000 accessing the network. 0:12:21.960000 --> 0:12:26.960000 Just some other sort of random facts here. 0:12:26.960000 --> 0:12:32.720000 So when the original invention of Ethernet was tested at the Palo Alto 0:12:32.720000 --> 0:12:37.180000 Research Center, the cabling that it used at that time was not like the 0:12:37.180000 --> 0:12:38.420000 cabling of Ethernet today. 0:12:38.420000 --> 0:12:42.720000 It was this real thick, not so easy to bend, sort of coaxial cable. 0:12:42.720000 --> 0:12:45.560000 And if you're not familiar with that term coaxial cable, just to think 0:12:45.560000 --> 0:12:48.160000 about your cable TV, right? 0:12:48.160000 --> 0:12:50.880000 That real thick cable that you plug into the wall and you plug into the 0:12:50.880000 --> 0:12:54.500000 back of your cable box, that is coaxial cable. 0:12:54.500000 --> 0:12:58.280000 So something very similar to that, but even thicker, was used by Ethernet 0:12:58.280000 --> 0:13:02.820000 at the time. And the way they developed this was that in the Palo Alto 0:13:02.820000 --> 0:13:07.680000 Research Center, down every hall, there would be this long coaxial cable 0:13:07.680000 --> 0:13:12.300000 running down the hall, running up and down vertically through the floors 0:13:12.300000 --> 0:13:13.460000 of the building. 0:13:13.460000 --> 0:13:16.860000 And the idea was all of these Xerox Altos and these laser printers would 0:13:16.860000 --> 0:13:19.440000 be physically tapped into this cable. 0:13:19.440000 --> 0:13:24.460000 So you literally had one long stretch of copper wire that all these devices 0:13:24.460000 --> 0:13:26.880000 were tapped into. 0:13:26.880000 --> 0:13:30.260000 And then they were using CSMA CD for access. 0:13:30.260000 --> 0:13:32.820000 One other thing I read, which is kind of interesting, is where did he 0:13:32.820000 --> 0:13:35.220000 come up with this term ether net? 0:13:35.220000 --> 0:13:36.980000 Where is the word ether comes from? 0:13:36.980000 --> 0:13:38.720000 It's actually kind of cool, the story behind that. 0:13:38.720000 --> 0:13:44.020000 So apparently back in the early 19th century, physicists were thinking 0:13:44.020000 --> 0:13:48.800000 about light. They were starting to explore with the idea of light, and 0:13:48.800000 --> 0:13:54.080000 they were trying to ask themselves, is light, is it matter, or is it energy? 0:13:54.080000 --> 0:13:55.960000 Which one is it, matter or energy? 0:13:55.960000 --> 0:13:58.680000 And they were looking at the properties of light. 0:13:58.680000 --> 0:14:01.080000 If you've ever done any research in physics, you know that some of the 0:14:01.080000 --> 0:14:05.940000 properties of light and the way it behaves, it's sort of like a wave, 0:14:05.940000 --> 0:14:06.820000 sort of like matter. 0:14:06.820000 --> 0:14:09.520000 It has characteristics of matter. 0:14:09.520000 --> 0:14:12.120000 It also has characteristics of energy as well. 0:14:12.120000 --> 0:14:14.840000 So these physicists thought, okay, we've got the sun, which is millions 0:14:14.840000 --> 0:14:17.280000 of miles away from the earth. 0:14:17.280000 --> 0:14:22.620000 If it's matter that it's sending to us, matter can't go through a vacuum. 0:14:22.620000 --> 0:14:24.500000 Something has to carry matter. 0:14:24.500000 --> 0:14:28.740000 And so these 19th century physicists, they came up with this idea that 0:14:28.740000 --> 0:14:34.620000 there was some invisible substance surrounding all in space. 0:14:34.620000 --> 0:14:38.240000 So what we think of as space, they actually thought there's some invisible 0:14:38.240000 --> 0:14:42.040000 substance out there. 0:14:42.040000 --> 0:14:46.120000 They called the luminous, what they call it here, the luminiferous ether. 0:14:46.120000 --> 0:14:47.200000 The luminiferous ether. 0:14:47.200000 --> 0:14:52.700000 They said that invisible substance is what's actually carrying light from 0:14:52.700000 --> 0:14:54.760000 the sun to the earth. 0:14:54.760000 --> 0:14:59.120000 So they said, here's some invisible passive medium, which is carrying 0:14:59.120000 --> 0:15:02.600000 electromagnetic waves. 0:15:02.600000 --> 0:15:08.260000 And so Dr. Metcalf said, well, I've got this cable, I've got this substance, 0:15:08.260000 --> 0:15:11.840000 which is passively just running all throughout the building up and down, 0:15:11.840000 --> 0:15:16.540000 left and right. Anything can tap into this substance, this cable. 0:15:16.540000 --> 0:15:21.340000 This substance is carrying electromagnetic energy. 0:15:21.340000 --> 0:15:23.680000 It's sort of like the luminiferous ether. 0:15:23.680000 --> 0:15:28.020000 So he called it ether net, a network made out of ether. 0:15:28.020000 --> 0:15:30.200000 And that's where he came up with the term for that. 0:15:30.200000 --> 0:15:37.680000 So an ether net first came out back in the mid 1970s. 0:15:37.680000 --> 0:15:41.040000 When it was very first tested at the Palo Alto Research Center, it was 0:15:41.040000 --> 0:15:45.580000 at a whopping 2.94 megabits per second. 0:15:45.580000 --> 0:15:48.760000 Wow, super fast. 0:15:48.760000 --> 0:15:53.160000 Then a little bit later Xerox partnered up with Digital Equipment Corporation 0:15:53.160000 --> 0:15:57.960000 and Intel. And all three of them said, you know what, we like this technology. 0:15:57.960000 --> 0:16:00.960000 We're going to start using it, we're going to start promoting it, and 0:16:00.960000 --> 0:16:03.780000 we're going to use it internally on all of our systems. 0:16:03.780000 --> 0:16:07.100000 So they created what's called the Dix consortium, standing for digital 0:16:07.100000 --> 0:16:13.120000 Intel in Xerox. And then they worked a little bit more on ether net, and 0:16:13.120000 --> 0:16:15.060000 then ether net version two came out. 0:16:15.060000 --> 0:16:17.540000 So they came out with ether net version two, and that's what ether net 0:16:17.540000 --> 0:16:20.020000 was first at 10 megabits per second. 0:16:20.020000 --> 0:16:23.860000 So most of us, when we think about the slowest ether net has ever been, 0:16:23.860000 --> 0:16:28.080000 we think of 10 megabit per second ether net, which nobody uses anymore. 0:16:28.080000 --> 0:16:30.300000 But it's actually kind of interesting that when it was first tested, it 0:16:30.300000 --> 0:16:33.680000 was only 2.94 megabits per second. 0:16:33.680000 --> 0:16:40.160000 So here we're looking at like the late 1970s, you know 1970s, maybe 1980. 0:16:40.160000 --> 0:16:44.280000 And then, so what happened was Dr. 0:16:44.280000 --> 0:16:49.820000 Robert Metcalf left Xerox and he decided, hey, people are liking what 0:16:49.820000 --> 0:16:52.780000 I created here. They seem to really be liking this thing. 0:16:52.780000 --> 0:16:55.960000 I've got digital and I've got Intel signed up. 0:16:55.960000 --> 0:17:00.180000 And he went and he created his own company called 3COM Corporation. 0:17:00.180000 --> 0:17:05.500000 And he went and formed a new IEEE committee, the 802 committee. 0:17:05.500000 --> 0:17:07.920000 So it's actually interesting that Dr. 0:17:07.920000 --> 0:17:11.580000 Robert Metcalf was one of the original founders of the 802 committee. 0:17:11.580000 --> 0:17:17.020000 On that committee, they created the 802.3 working group and the 802.3 0:17:17.020000 --> 0:17:22.160000 working group in formalized ether net as 802.3. 0:17:22.160000 --> 0:17:29.400000 Then in 1995, so now we're looking at about 15 years later, the IEEE introduced 0:17:29.400000 --> 0:17:34.040000 the 802.3 U standard and dramatically increased the speed to 100 megabits 0:17:34.040000 --> 0:17:37.880000 per second. So now we're looking at what we call fast ether net. 0:17:37.880000 --> 0:17:42.320000 Now you can see here that there's less and less time being elapsed in 0:17:42.320000 --> 0:17:46.140000 shorter periods where ether is getting faster and faster and faster. 0:17:46.140000 --> 0:17:53.100000 So in 1998, gigabit ether net was introduced, 1 billion bits per second. 0:17:53.100000 --> 0:17:59.300000 In 2002, 10 gigabit ether net came out. 0:17:59.300000 --> 0:18:06.140000 And in 2010, the IEEE 802.3 BA standard was ratified, which standardized 0:18:06.140000 --> 0:18:10.340000 40 gigabit and 100 gigabit ether net. 0:18:10.340000 --> 0:18:14.480000 Which is still kind of hard to get interfaces that support that, but that 0:18:14.480000 --> 0:18:20.640000 did come out. So where does ether net fall within the scope of the OSI 0:18:20.640000 --> 0:18:23.500000 model, the open systems interconnect? 0:18:23.500000 --> 0:18:28.280000 So we know the OSI model is 7 layers, application layer down through the 0:18:28.280000 --> 0:18:33.580000 physical layer. So if you're actually to open up the 802.3 specification 0:18:33.580000 --> 0:18:37.620000 or the old ether net version 2 specification, one thing you would notice 0:18:37.620000 --> 0:18:40.420000 is it specifies the physical layer. 0:18:40.420000 --> 0:18:43.240000 Actually, these lines don't really quite add up a little bit, but that's 0:18:43.240000 --> 0:18:47.620000 all right. So, and the physical layer, they sort of divide that into two 0:18:47.620000 --> 0:18:48.520000 different sub layers. 0:18:48.520000 --> 0:18:53.700000 You've got media specifications, which is sort of like, okay, what's the 0:18:53.700000 --> 0:18:55.080000 net car going to look like? 0:18:55.080000 --> 0:18:56.260000 Is it made of plastic? 0:18:56.260000 --> 0:18:57.360000 Is it made of metal? 0:18:57.360000 --> 0:18:58.900000 How thick is the metal? 0:18:58.900000 --> 0:18:59.680000 How where's the plan? 0:18:59.680000 --> 0:19:01.760000 How many pins are in there? 0:19:01.760000 --> 0:19:03.700000 How are we connecting this stuff together? 0:19:03.700000 --> 0:19:06.300000 So that would all be the media specifications. 0:19:06.300000 --> 0:19:09.580000 And then you have the physical signaling sub layer, which is in charge 0:19:09.580000 --> 0:19:14.080000 of things like, okay, how are we going to use electricity to specify a 0:19:14.080000 --> 0:19:19.280000 1? Specify a 0. If I'm changing the voltage to be a certain voltage level 0:19:19.280000 --> 0:19:22.200000 for 1, how long do I hold it at that level? 0:19:22.200000 --> 0:19:25.460000 So all that stuff dealing with electricity and how we use that to represent 0:19:25.460000 --> 0:19:29.280000 binary is in the physical signaling sub layer. 0:19:29.280000 --> 0:19:34.560000 And that the data link layer, that's also subdivided into two sub layers. 0:19:34.560000 --> 0:19:37.700000 You've got the media access control sub layer. 0:19:37.700000 --> 0:19:41.080000 And the media access control sub layer is the sub layer of the data link 0:19:41.080000 --> 0:19:45.960000 layer that says things like, what are the rules for accessing the physical 0:19:45.960000 --> 0:19:48.340000 layer? Can I talk whenever I want? 0:19:48.340000 --> 0:19:49.620000 Or do I have to wait? 0:19:49.620000 --> 0:19:52.440000 If I have to wait, how long do I wait? 0:19:52.440000 --> 0:19:55.460000 When I do start talking, how long can I start talking? 0:19:55.460000 --> 0:19:59.180000 How long can I start transmitting data until I have to stop? 0:19:59.180000 --> 0:20:00.860000 When data is coming in? 0:20:00.860000 --> 0:20:04.260000 How do I know if it's for me or for somebody else? 0:20:04.260000 --> 0:20:07.700000 Should I use an address so somebody wants to send data to me they know 0:20:07.700000 --> 0:20:08.540000 what my address is? 0:20:08.540000 --> 0:20:11.340000 And if so, what does that address look like? 0:20:11.340000 --> 0:20:15.140000 All those types of things are answered at the media access control sub 0:20:15.140000 --> 0:20:21.100000 layer. And then above that, you have the logical link control sub layer, 0:20:21.100000 --> 0:20:27.540000 which defines, okay, how do multiple things at layer 3, for example, IPv4, 0:20:27.540000 --> 0:20:32.980000 IPv6, Apple Talk, Netware, you know, all sorts of other stuff. 0:20:32.980000 --> 0:20:38.240000 How do they all make use of this layer 2 protocol? 0:20:38.240000 --> 0:20:42.440000 And how, when a layer 2 frame is coming in, how do we send it up to the 0:20:42.440000 --> 0:20:46.360000 appropriate layer 3 process that's running in the CPU? 0:20:46.360000 --> 0:20:50.500000 That's all defined at the logical link control sub layer. 0:20:50.500000 --> 0:20:55.300000 So as far as the Ethernet specification, as far as 802.3 is concerned, 0:20:55.300000 --> 0:20:59.020000 if you were to open up the 802.3 document, you would see that it specifies 0:20:59.020000 --> 0:21:00.440000 those things in blue there. 0:21:00.440000 --> 0:21:04.240000 So from media specifications, all the way up to the media access control 0:21:04.240000 --> 0:21:09.420000 sub layer. It does not specify the logical link control sub layer. 0:21:09.420000 --> 0:21:14.100000 There was actually a different working group called the 802.2 working 0:21:14.100000 --> 0:21:17.320000 group. Remember 802 .3 was Ethernet. 0:21:17.320000 --> 0:21:20.880000 802.2 was the logical link control sub layer. 0:21:20.880000 --> 0:21:23.460000 And they create a whole unique working group for that because they said, 0:21:23.460000 --> 0:21:27.300000 hey, what we come up with, we actually want that to be applicable across 0:21:27.300000 --> 0:21:29.460000 other layer 2 technologies. 0:21:29.460000 --> 0:21:34.980000 We would like to come up with a way of how multiple things that layer 0:21:34.980000 --> 0:21:42.420000 3 can access Ethernet, token ring, FITI, and maybe other layer 2 technologies, 0:21:42.420000 --> 0:21:43.980000 not just Ethernet. 0:21:43.980000 --> 0:21:45.060000 So that's why it's separate. 0:21:45.060000 --> 0:21:47.940000 That's why it's in its own separate white box here. 0:21:47.940000 --> 0:21:52.600000 So that concludes this section on Ethernet history and overview. 0:21:52.600000 --> 0:21:55.760000 And in the next section, we'll be talking about carrier sense multiple 0:21:55.760000 --> 0:21:57.680000 access with collision detect.