1 1 00:00:00,750 --> 00:00:03,940 In the last lesson, we just finished talking about DSL. 2 2 00:00:03,940 --> 00:00:06,220 And I mentioned that there was a decline in popularity, 3 3 00:00:06,220 --> 00:00:09,520 because cable modems and fiber modems started taking over. 4 4 00:00:09,520 --> 00:00:12,280 So let's talk about cable modems for a moment. 5 5 00:00:12,280 --> 00:00:14,550 Cable modems use the cable TV network, 6 6 00:00:14,550 --> 00:00:17,450 which is made up of a hybrid fiber-coax solution, 7 7 00:00:17,450 --> 00:00:19,040 known as HFC, 8 8 00:00:19,040 --> 00:00:21,540 and this is the type of distribution network it has. 9 9 00:00:21,540 --> 00:00:24,110 If you see the term HFC on the exam, 10 10 00:00:24,110 --> 00:00:26,790 remember we're talking about cable modems here. 11 11 00:00:26,790 --> 00:00:29,040 Now cable TV can write on top of it, 12 12 00:00:29,040 --> 00:00:31,180 but so can our internet signals. 13 13 00:00:31,180 --> 00:00:33,470 And so this mixture of coax and fiber cables 14 14 00:00:33,470 --> 00:00:34,930 made it very fast. 15 15 00:00:34,930 --> 00:00:36,620 They're specific frequency ranges 16 16 00:00:36,620 --> 00:00:39,310 that are used for upstream and downstream transmissions, 17 17 00:00:39,310 --> 00:00:41,680 as determined by a standard called DOCSIS, 18 18 00:00:41,680 --> 00:00:45,240 which is Data-Over-Cable Service Interface Specification. 19 19 00:00:45,240 --> 00:00:47,120 D-O-C-S-I-S. 20 20 00:00:47,120 --> 00:00:48,900 So again, for the exam, 21 21 00:00:48,900 --> 00:00:52,240 anytime you see HFC or D-O-C-S-I-S, 22 22 00:00:52,240 --> 00:00:53,510 I want you to think about the answer 23 23 00:00:53,510 --> 00:00:55,830 being something to do with cable modems. 24 24 00:00:55,830 --> 00:00:59,280 Now, upstream, these use between five and 42 megahertz, 25 25 00:00:59,280 --> 00:01:02,960 and downstream, they use between 50 and 860 megahertz. 26 26 00:01:02,960 --> 00:01:05,380 Don't worry about those frequencies for the exam, 27 27 00:01:05,380 --> 00:01:08,130 just remember the terms HFC and DOCSIS 28 28 00:01:08,130 --> 00:01:11,080 are associated with cable modems, and you'll do fine. 29 29 00:01:11,080 --> 00:01:13,340 Now, these systems can transmit and receive 30 30 00:01:13,340 --> 00:01:15,690 over the current cable TV infrastructure, 31 31 00:01:15,690 --> 00:01:17,950 which is already rolled out to most of America 32 32 00:01:17,950 --> 00:01:19,720 and many other places worldwide. 33 33 00:01:19,720 --> 00:01:22,200 And this made it a very quick sell to get cable modems 34 34 00:01:22,200 --> 00:01:23,620 into the marketplace, 35 35 00:01:23,620 --> 00:01:26,220 and they offered increased speed over DSL, 36 36 00:01:26,220 --> 00:01:28,430 which made them even more popular. 37 37 00:01:28,430 --> 00:01:29,470 Now, the next one we have, 38 38 00:01:29,470 --> 00:01:31,190 is what's known as a satellite modem. 39 39 00:01:31,190 --> 00:01:32,970 I've already mentioned satellites a little bit, 40 40 00:01:32,970 --> 00:01:34,490 but I want to go a little bit more in-depth here, 41 41 00:01:34,490 --> 00:01:36,830 because now we're talking about the technology itself 42 42 00:01:36,830 --> 00:01:38,560 and not just the concept. 43 43 00:01:38,560 --> 00:01:40,980 Satellite modems are used in remote, rural, 44 44 00:01:40,980 --> 00:01:42,610 or disconnected locations. 45 45 00:01:42,610 --> 00:01:44,910 Like if you're out to sea or you're in some farmland 46 46 00:01:44,910 --> 00:01:46,300 in the middle of nowhere. 47 47 00:01:46,300 --> 00:01:49,290 Now satellite modems provide us with relatively fast speeds, 48 48 00:01:49,290 --> 00:01:50,720 like a DSL modem, 49 49 00:01:50,720 --> 00:01:53,940 but not nearly as speeds of cable or fiber. 50 50 00:01:53,940 --> 00:01:55,570 Now, the bad thing about satellite, 51 51 00:01:55,570 --> 00:01:58,380 is that it provides us with very low usage caps. 52 52 00:01:58,380 --> 00:01:59,499 Now, what I mean by that is, 53 53 00:01:59,499 --> 00:02:01,450 if you're going to do a lot of streaming video services, 54 54 00:02:01,450 --> 00:02:03,870 satellite is probably not the right answer for you, 55 55 00:02:03,870 --> 00:02:05,130 because they may only let you have 56 56 00:02:05,130 --> 00:02:07,670 five or 10 gigabytes per month of service, 57 57 00:02:07,670 --> 00:02:10,510 and after that, you'd end up having to pay a lot more money. 58 58 00:02:10,510 --> 00:02:12,800 If you end up watching a couple hours of Netflix, 59 59 00:02:12,800 --> 00:02:15,150 you can quickly use a gigabyte or more of data, 60 60 00:02:15,150 --> 00:02:16,990 and so this is a concern. 61 61 00:02:16,990 --> 00:02:19,090 Now, there are some other issues with using satellite 62 62 00:02:19,090 --> 00:02:20,620 that you have to be concerned with, 63 63 00:02:20,620 --> 00:02:22,660 and one of them is the delay. 64 64 00:02:22,660 --> 00:02:24,540 You have to realize that when you're going from up 65 65 00:02:24,540 --> 00:02:26,010 to a satellite and down, 66 66 00:02:26,010 --> 00:02:27,700 you're not just going across the country, 67 67 00:02:27,700 --> 00:02:29,810 but you're actually going all the way out to space. 68 68 00:02:29,810 --> 00:02:31,140 And if you have your satellite terminal 69 69 00:02:31,140 --> 00:02:32,550 going all the way up to space, 70 70 00:02:32,550 --> 00:02:34,560 and then all the way down to a ground station, 71 71 00:02:34,560 --> 00:02:36,300 that adds up time. 72 72 00:02:36,300 --> 00:02:38,490 Every time the satellite has to go up and down 73 73 00:02:38,490 --> 00:02:39,370 from the satellite, 74 74 00:02:39,370 --> 00:02:42,430 there's about a quarter of a second right off the bat delay. 75 75 00:02:42,430 --> 00:02:43,460 So if you're trying to do something like 76 76 00:02:43,460 --> 00:02:45,600 Voice over IP over satellite, 77 77 00:02:45,600 --> 00:02:47,570 you're going to have this kind of echo-y sound, 78 78 00:02:47,570 --> 00:02:49,230 because there's a delay in your voice. 79 79 00:02:49,230 --> 00:02:50,180 It's like, hey, hey, 80 80 00:02:50,180 --> 00:02:51,013 how, how, 81 81 00:02:51,013 --> 00:02:51,846 are, are, 82 82 00:02:51,846 --> 00:02:52,679 you, you? 83 83 00:02:52,679 --> 00:02:54,560 It just gets really annoying. 84 84 00:02:54,560 --> 00:02:56,120 Well, when you have that connectivity 85 85 00:02:56,120 --> 00:02:58,760 versus no connectivity, it really is better than nothing. 86 86 00:02:58,760 --> 00:03:00,140 But if you have another choice, 87 87 00:03:00,140 --> 00:03:02,850 you probably want to choose something other than satellite. 88 88 00:03:02,850 --> 00:03:04,420 Now, the other issue with satellite 89 89 00:03:04,420 --> 00:03:06,290 is that there's weather issues too. 90 90 00:03:06,290 --> 00:03:08,880 Anytime you have a big thunderstorm or a snowstorm, 91 91 00:03:08,880 --> 00:03:09,890 that's putting interference 92 92 00:03:09,890 --> 00:03:12,790 between your satellite dish and the satellite in space, 93 93 00:03:12,790 --> 00:03:15,530 and this can cause issues and cause loss of service. 94 94 00:03:15,530 --> 00:03:18,070 Also, if the ground station that you're connecting to, 95 95 00:03:18,070 --> 00:03:20,940 has rain delays in their area or snow in their area, 96 96 00:03:20,940 --> 00:03:23,190 that can actually cause service issues for you, 97 97 00:03:23,190 --> 00:03:25,810 even if you have good weather in your area. 98 98 00:03:25,810 --> 00:03:27,320 Now, the next one we need to talk about, 99 99 00:03:27,320 --> 00:03:31,140 is what's known as the Plain Old Telephone Service or POTS. 100 100 00:03:31,140 --> 00:03:33,400 POTS runs on what's called the PSTN, 101 101 00:03:33,400 --> 00:03:35,970 or the public switched telephone network. 102 102 00:03:35,970 --> 00:03:37,790 This consists of all the telephone carriers 103 103 00:03:37,790 --> 00:03:39,490 from around the globe. 104 104 00:03:39,490 --> 00:03:42,320 I can make a phone call from my house to my neighbor's house 105 105 00:03:42,320 --> 00:03:44,890 or from my house to the other side of the world, 106 106 00:03:44,890 --> 00:03:48,480 and it's still running on the PSTN using POTS service. 107 107 00:03:48,480 --> 00:03:50,770 This is what we call analog phone service, 108 108 00:03:50,770 --> 00:03:53,640 and it's all based on beeps and bops. 109 109 00:03:53,640 --> 00:03:56,410 Now these analog connections can be voiced when I'm talking, 110 110 00:03:56,410 --> 00:03:59,440 or it can be data that's being converted from ones and zeros 111 111 00:03:59,440 --> 00:04:03,110 into a modulation of that sound using those beeps and bops. 112 112 00:04:03,110 --> 00:04:05,320 This is how PSTN works. 113 113 00:04:05,320 --> 00:04:07,300 Now, these are often called dial-up connections 114 114 00:04:07,300 --> 00:04:08,780 or POTS connections. 115 115 00:04:08,780 --> 00:04:10,650 Now, if you're an older person like me, 116 116 00:04:10,650 --> 00:04:13,160 you might've used a dial-up modem back in the day. 117 117 00:04:13,160 --> 00:04:15,040 You might remember the dial-up modems 118 118 00:04:15,040 --> 00:04:18,850 have a maximum bandwidth of 53.3 kilobits per second, 119 119 00:04:18,850 --> 00:04:20,730 which means they're really slow. 120 120 00:04:20,730 --> 00:04:21,850 The reason for this, 121 121 00:04:21,850 --> 00:04:24,330 is the phone system worked on these T1 channels, 122 122 00:04:24,330 --> 00:04:27,000 and each one is only 64 kilobits per second. 123 123 00:04:27,000 --> 00:04:28,150 And so essentially, 124 124 00:04:28,150 --> 00:04:31,240 POTS ran over the same technology as a T1 connection, 125 125 00:04:31,240 --> 00:04:33,490 or 1/24th of a T1 connection. 126 126 00:04:33,490 --> 00:04:37,040 So when you made a phone call, you only had access to 64k, 127 127 00:04:37,040 --> 00:04:39,470 and part of that was being eaten up by overhead, 128 128 00:04:39,470 --> 00:04:42,990 so you got a maximum of 53.3 kilobits per second. 129 129 00:04:42,990 --> 00:04:45,460 Now I just gave you a lot of information about dial-up, 130 130 00:04:45,460 --> 00:04:47,590 and you really don't need to memorize all the specifics 131 131 00:04:47,590 --> 00:04:50,950 because honestly, most people don't use dial-up anymore. 132 132 00:04:50,950 --> 00:04:52,800 In fact, if you're still running dial-up, 133 133 00:04:52,800 --> 00:04:54,270 you're not watching this video, 134 134 00:04:54,270 --> 00:04:56,280 because it's just not fast enough, right? 135 135 00:04:56,280 --> 00:04:58,610 It's too darn slow for anything you really want to do 136 136 00:04:58,610 --> 00:05:00,420 on the real internet nowadays. 137 137 00:05:00,420 --> 00:05:02,960 But you may find it in some very specialized, 138 138 00:05:02,960 --> 00:05:04,370 unique situations, 139 139 00:05:04,370 --> 00:05:07,030 or what we call legacy systems in your network. 140 140 00:05:07,030 --> 00:05:09,600 Now legacy system means it's an old system, 141 141 00:05:09,600 --> 00:05:11,620 but we still need it for some critical function, 142 142 00:05:11,620 --> 00:05:13,470 and it just can't work on the internet itself, 143 143 00:05:13,470 --> 00:05:16,070 so it still relies on something like a dial-up modem. 144 144 00:05:16,070 --> 00:05:17,810 Now for the home and office user, 145 145 00:05:17,810 --> 00:05:20,200 you're just not going to find these dial-up modems anymore, 146 146 00:05:20,200 --> 00:05:22,500 because most people just don't use them. 147 147 00:05:22,500 --> 00:05:25,090 You may find something known as ISDN though, 148 148 00:05:25,090 --> 00:05:27,720 which is the Integrated Service Digital Network. 149 149 00:05:27,720 --> 00:05:29,570 Now, I mentioned this briefly when we talked about 150 150 00:05:29,570 --> 00:05:31,070 circuit switch technologies, 151 151 00:05:31,070 --> 00:05:32,960 because ISDN is a great example 152 152 00:05:32,960 --> 00:05:35,040 of a circuit switch technology. 153 153 00:05:35,040 --> 00:05:38,200 It supports taking multiple 64k bearer channels 154 154 00:05:38,200 --> 00:05:39,540 and putting them together. 155 155 00:05:39,540 --> 00:05:41,080 So it works a lot like dial-up, 156 156 00:05:41,080 --> 00:05:43,230 but you could bind those channels together 157 157 00:05:43,230 --> 00:05:46,080 and get speeds up to a T1 connection. 158 158 00:05:46,080 --> 00:05:48,240 Now, again, this is an older technology, 159 159 00:05:48,240 --> 00:05:50,360 designed to carry voice, video, or data 160 160 00:05:50,360 --> 00:05:52,880 over these B channels, these bearer channels. 161 161 00:05:52,880 --> 00:05:56,120 They also had D channels, which were data or delta channels, 162 162 00:05:56,120 --> 00:05:57,600 that existed for signaling, 163 163 00:05:57,600 --> 00:05:59,480 that was able to do control measures. 164 164 00:05:59,480 --> 00:06:01,810 Now we're not going to go too in-depth into ISDN here, 165 165 00:06:01,810 --> 00:06:04,530 because honestly, you're probably never going to run across one 166 166 00:06:04,530 --> 00:06:06,770 in the real world here in 2020, 167 167 00:06:06,770 --> 00:06:09,260 because most people have already moved to cable, or fiber, 168 168 00:06:09,260 --> 00:06:11,120 or even a T1 connection. 169 169 00:06:11,120 --> 00:06:13,610 But if you work for some organizations, 170 170 00:06:13,610 --> 00:06:15,480 they may have some legacy thing out there 171 171 00:06:15,480 --> 00:06:16,780 that still has an ISDN. 172 172 00:06:16,780 --> 00:06:19,260 I actually ran into one about six months ago, 173 173 00:06:19,260 --> 00:06:20,720 when I was doing some contracting. 174 174 00:06:20,720 --> 00:06:23,990 So it is something you may come across, but not likely. 175 175 00:06:23,990 --> 00:06:27,110 Now these again, were popular back in the late 90s. 176 176 00:06:27,110 --> 00:06:30,400 And when we dealt with T1s, they work the same kind of way. 177 177 00:06:30,400 --> 00:06:33,717 They had two different circuits, they had BRIs and PRIs. 178 178 00:06:33,717 --> 00:06:35,740 BRIs are Basic Rate Interface, 179 179 00:06:35,740 --> 00:06:38,090 and PRIs are Primary Rate Interface. 180 180 00:06:38,090 --> 00:06:40,650 With the Basic Rate Interface for ISDN, 181 181 00:06:40,650 --> 00:06:43,100 it would give you 128 kilobits per second 182 182 00:06:43,100 --> 00:06:45,490 by tying two B channels together. 183 183 00:06:45,490 --> 00:06:48,170 PRI, on the other hand, would give you about T1 speeds 184 184 00:06:48,170 --> 00:06:50,820 by taking 23 B channels, putting them together, 185 185 00:06:50,820 --> 00:06:53,220 and then using one as a data channel. 186 186 00:06:53,220 --> 00:06:55,070 Now, the next technology we want to talk about, 187 187 00:06:55,070 --> 00:06:56,220 is frame relay. 188 188 00:06:56,220 --> 00:06:58,130 And this is losing market share as well, 189 189 00:06:58,130 --> 00:07:01,050 due to the cheapness of cable and DSL. 190 190 00:07:01,050 --> 00:07:04,270 Frame relay was where we were able to use virtual circuits. 191 191 00:07:04,270 --> 00:07:06,930 If I had two branch offices and a headquarters, 192 192 00:07:06,930 --> 00:07:08,630 I could connect them through point-to-point, 193 193 00:07:08,630 --> 00:07:11,950 or point to multi-point as shown in this diagram. 194 194 00:07:11,950 --> 00:07:14,310 Now, this is a point to multi-point connection, 195 195 00:07:14,310 --> 00:07:17,010 and they were low-cost and widely available. 196 196 00:07:17,010 --> 00:07:19,030 It provided always on or on-demand, 197 197 00:07:19,030 --> 00:07:20,670 depending on how much you wanted to pay, 198 198 00:07:20,670 --> 00:07:23,340 and these were considered a Layer 2 technology. 199 199 00:07:23,340 --> 00:07:25,870 Now frame relay was really great for a long time, 200 200 00:07:25,870 --> 00:07:29,240 but because of the lower cost of fiber, cable, and DSL, 201 201 00:07:29,240 --> 00:07:31,640 most small business environments switched away 202 202 00:07:31,640 --> 00:07:35,240 from frame relay and into one of those solutions instead. 203 203 00:07:35,240 --> 00:07:36,850 Next, we have SONET, 204 204 00:07:36,850 --> 00:07:39,510 and SONET is a Synchronous Optical Network. 205 205 00:07:39,510 --> 00:07:43,290 It is a Layer 1 technology that uses fiber as its media. 206 206 00:07:43,290 --> 00:07:46,000 Now, this is fast, really, really fast. 207 207 00:07:46,000 --> 00:07:47,700 Now, when we talk about T1 connections, 208 208 00:07:47,700 --> 00:07:50,690 we were talking about 1.5 megabits per second. 209 209 00:07:50,690 --> 00:07:52,380 When we talked about a T3 connection, 210 210 00:07:52,380 --> 00:07:54,950 we were talking about 45 megabits per second. 211 211 00:07:54,950 --> 00:07:56,480 When I'm talking about SONET, 212 212 00:07:56,480 --> 00:07:59,950 I'm talking about speeds of 155 megabits per second 213 213 00:07:59,950 --> 00:08:01,080 to start with, 214 214 00:08:01,080 --> 00:08:01,913 and then they go up 215 215 00:08:01,913 --> 00:08:05,040 all the way to 10 gigabits per second or more. 216 216 00:08:05,040 --> 00:08:07,290 SONET uses Transport Layer 2 encryption, 217 217 00:08:07,290 --> 00:08:09,940 like ATM or Asynchronous Transfer Mode, 218 218 00:08:09,940 --> 00:08:11,750 to do all the shaping of those frames 219 219 00:08:11,750 --> 00:08:13,360 and really send stuff around 220 220 00:08:13,360 --> 00:08:14,670 really, really fast, 221 221 00:08:14,670 --> 00:08:15,920 because it's all fiber, 222 222 00:08:15,920 --> 00:08:17,970 and it can go really long distances too, 223 223 00:08:17,970 --> 00:08:21,300 of 20 to 250 kilometers or more. 224 224 00:08:21,300 --> 00:08:22,820 Now the physical topology of this, 225 225 00:08:22,820 --> 00:08:24,860 can be either a bus or a ring. 226 226 00:08:24,860 --> 00:08:27,220 I've seen this implemented as what's known as a FDDI ring, 227 227 00:08:27,220 --> 00:08:28,920 a fiber distribution ring, 228 228 00:08:28,920 --> 00:08:31,900 which has two counter-rotating rings for redundancy. 229 229 00:08:31,900 --> 00:08:34,180 ATM then rides on top of SONET, 230 230 00:08:34,180 --> 00:08:37,050 and this is the Layer 2 way of shaping those frames 231 231 00:08:37,050 --> 00:08:38,720 and sending them over the network, 232 232 00:08:38,720 --> 00:08:41,940 much like we'd use Ethernet over copper cabling. 233 233 00:08:41,940 --> 00:08:44,290 Now this is going to use two different things. 234 234 00:08:44,290 --> 00:08:48,130 We can either have the permanent virtual circuits or PVCs, 235 235 00:08:48,130 --> 00:08:51,620 or we can use switched virtual circuits, SVCs. 236 236 00:08:51,620 --> 00:08:52,760 It's like frame relay, 237 237 00:08:52,760 --> 00:08:54,980 except all the frames have a fixed-length, 238 238 00:08:54,980 --> 00:08:56,340 and we call these cells, 239 239 00:08:56,340 --> 00:08:58,590 and we can move them around really, really fast 240 240 00:08:58,590 --> 00:09:00,200 because they're all fixed rate. 241 241 00:09:00,200 --> 00:09:01,610 And as we move them around, 242 242 00:09:01,610 --> 00:09:04,170 it's known as a protocol data unit. 243 243 00:09:04,170 --> 00:09:05,850 Now because they're all fixed-length, 244 244 00:09:05,850 --> 00:09:07,300 and they have the shortened header, 245 245 00:09:07,300 --> 00:09:09,170 which is only five bytes in size, 246 246 00:09:09,170 --> 00:09:10,570 this is going to save us a lot of time 247 247 00:09:10,570 --> 00:09:13,080 and makes things much, much faster. 248 248 00:09:13,080 --> 00:09:14,670 As you can see here on the diagram, 249 249 00:09:14,670 --> 00:09:17,370 I broke out what an ATM header looks like for you. 250 250 00:09:17,370 --> 00:09:19,070 Again, you don't have to memorize 251 251 00:09:19,070 --> 00:09:20,670 all of these pieces and parts, 252 252 00:09:20,670 --> 00:09:24,550 but do realize that ATM has a fixed header of five bytes, 253 253 00:09:24,550 --> 00:09:26,520 and a payload of 48 bytes, 254 254 00:09:26,520 --> 00:09:29,320 giving us a 53-byte cell for ATM, 255 255 00:09:29,320 --> 00:09:31,670 and because it's the same each and every time, 256 256 00:09:31,670 --> 00:09:34,940 it's really easy and really fast for us to move it around. 257 257 00:09:34,940 --> 00:09:37,100 When we look at ATM virtual circuits, 258 258 00:09:37,100 --> 00:09:39,420 they are designated in two different ways. 259 259 00:09:39,420 --> 00:09:41,910 The user-network interface or UNI, 260 260 00:09:41,910 --> 00:09:44,870 is what connects the ATM switches to the end points. 261 261 00:09:44,870 --> 00:09:47,400 Then we have these network node interfaces, 262 262 00:09:47,400 --> 00:09:50,210 and we connect the ATM switches together using those. 263 263 00:09:50,210 --> 00:09:53,100 Again, you don't need to know this in too much depth, 264 264 00:09:53,100 --> 00:09:56,200 except to know that if you see the terms ATM, 265 265 00:09:56,200 --> 00:09:57,490 when it comes to testing day, 266 266 00:09:57,490 --> 00:09:59,560 you need to realize that deals with fiber 267 267 00:09:59,560 --> 00:10:01,470 and SONET networks. 268 268 00:10:01,470 --> 00:10:04,410 The next one we have is what's known as MPLS, 269 269 00:10:04,410 --> 00:10:06,780 or Multiprotocol Label Switching. 270 270 00:10:06,780 --> 00:10:08,720 Now Multiprotocol Label Switching, 271 271 00:10:08,720 --> 00:10:11,930 is going to support multiple protocols on the same network. 272 272 00:10:11,930 --> 00:10:15,190 MPLS is not something you're going to use in your networks, 273 273 00:10:15,190 --> 00:10:17,380 but it is something that your service provider uses 274 274 00:10:17,380 --> 00:10:19,660 as the backbone for their networks. 275 275 00:10:19,660 --> 00:10:21,910 This can support frame relay and ATM 276 276 00:10:21,910 --> 00:10:24,030 on the same MPLS backbone, 277 277 00:10:24,030 --> 00:10:26,380 and because this is all using switching and labeling 278 278 00:10:26,380 --> 00:10:27,660 to transfer things around, 279 279 00:10:27,660 --> 00:10:30,250 it is extremely fast and works really well 280 280 00:10:30,250 --> 00:10:31,880 for backbone networks. 281 281 00:10:31,880 --> 00:10:33,850 This allows traffic to be dynamically routed 282 282 00:10:33,850 --> 00:10:37,000 based on low conditions and path availability. 283 283 00:10:37,000 --> 00:10:40,220 Now, using this label switching, it is much more efficient 284 284 00:10:40,220 --> 00:10:42,870 than standard logical Layer 3 IP addressing. 285 285 00:10:42,870 --> 00:10:44,620 And so it makes really quick work 286 286 00:10:44,620 --> 00:10:46,320 of all the routing and switching for us, 287 287 00:10:46,320 --> 00:10:48,500 as we take things around the globe. 288 288 00:10:48,500 --> 00:10:51,760 Again, this is used by backbone service providers, 289 289 00:10:51,760 --> 00:10:53,720 not us in our own networks. 290 290 00:10:53,720 --> 00:10:56,040 If you're working for a large telecom company, 291 291 00:10:56,040 --> 00:10:57,870 you may run into MPLS, 292 292 00:10:57,870 --> 00:11:00,410 but in your own small office, or home office, 293 293 00:11:00,410 --> 00:11:04,050 or medium-sized business, you're not going to see MPLS. 294 294 00:11:04,050 --> 00:11:05,560 MPLS is something the customer 295 295 00:11:05,560 --> 00:11:07,810 doesn't even know that exists half the time. 296 296 00:11:07,810 --> 00:11:11,250 It all happens behind the scenes at the service provider. 297 297 00:11:11,250 --> 00:11:14,360 Now, the last one we want to talk about is DMVPN. 298 298 00:11:14,360 --> 00:11:18,040 And this is the Dynamic Multipoint Virtual Private Network. 299 299 00:11:18,040 --> 00:11:19,650 This allows the internet itself, 300 300 00:11:19,650 --> 00:11:21,520 to be used as a WAN connection for us 301 301 00:11:21,520 --> 00:11:23,250 between two different sites and use it 302 302 00:11:23,250 --> 00:11:24,940 for secure communication. 303 303 00:11:24,940 --> 00:11:26,290 You can create a VPN tunnel 304 304 00:11:26,290 --> 00:11:28,130 with authentication and encryption, 305 305 00:11:28,130 --> 00:11:29,930 so the user on the unsecured network 306 306 00:11:29,930 --> 00:11:31,760 can't even see what you're doing. 307 307 00:11:31,760 --> 00:11:34,320 For example, if I have a couple of regional offices, 308 308 00:11:34,320 --> 00:11:36,790 I can connect them together over a VPN, 309 309 00:11:36,790 --> 00:11:39,710 instead of buying dedicated point-to-point connections. 310 310 00:11:39,710 --> 00:11:42,560 This allows me to buy maybe a cable modem or a DSL 311 311 00:11:42,560 --> 00:11:45,580 in that regional office for 50 or 100 dollars a month, 312 312 00:11:45,580 --> 00:11:48,280 instead of having to buy a dedicated T1 connection 313 313 00:11:48,280 --> 00:11:50,510 between my head office and my regional office, 314 314 00:11:50,510 --> 00:11:52,250 that can cost me thousands. 315 315 00:11:52,250 --> 00:11:54,440 This saves me a lot of time, and a lot of money, 316 316 00:11:54,440 --> 00:11:56,920 and I can connect remote users with low cost, 317 317 00:11:56,920 --> 00:11:59,720 without dedicated or leased line access. 318 318 00:11:59,720 --> 00:12:01,510 Now we're going to talk a lot more about VPNs 319 319 00:12:01,510 --> 00:12:02,590 in their own lecture, 320 320 00:12:02,590 --> 00:12:04,360 when we get into the network security section 321 321 00:12:04,360 --> 00:12:06,070 later on in the course. 322 322 00:12:06,070 --> 00:12:08,520 Now, I also want to talk about data rates here. 323 323 00:12:08,520 --> 00:12:09,790 When we talk about data rates, 324 324 00:12:09,790 --> 00:12:12,190 there are a couple of things that you just have to memorize. 325 325 00:12:12,190 --> 00:12:15,130 And so this chart is one that you should add to your notes. 326 326 00:12:15,130 --> 00:12:17,680 Bandwidth can be measured in kilobits per second, 327 327 00:12:17,680 --> 00:12:20,990 megabits per second, or gigabits per second. 328 328 00:12:20,990 --> 00:12:23,690 ATM and SONET are measured by optical carriers, 329 329 00:12:23,690 --> 00:12:25,450 known as OC connections. 330 330 00:12:25,450 --> 00:12:27,070 They start out with OC-1, 331 331 00:12:27,070 --> 00:12:29,880 which is 51.84 megabits per second, 332 332 00:12:29,880 --> 00:12:32,230 and everything else becomes a multiple of it. 333 333 00:12:32,230 --> 00:12:36,430 So if you have an OC-3, that is three times 51.84. 334 334 00:12:36,430 --> 00:12:40,200 If you're using an OC-12, it's 12 times 51.84. 335 335 00:12:40,200 --> 00:12:41,210 And so here on the chart, 336 336 00:12:41,210 --> 00:12:43,720 I'm going to show you a couple that you need to memorize. 337 337 00:12:43,720 --> 00:12:47,220 First, frame relay goes from 56 kilobits per second, 338 338 00:12:47,220 --> 00:12:48,700 which is a dial-up connection, 339 339 00:12:48,700 --> 00:12:50,480 all the way up to a T1 connection 340 340 00:12:50,480 --> 00:12:52,870 of 1.5 megabits per second. 341 341 00:12:52,870 --> 00:12:56,020 A T1 connection is 1.5 megabits per second. 342 342 00:12:56,020 --> 00:12:59,010 A T3 is 45 megabits per second. 343 343 00:12:59,010 --> 00:13:01,800 An E1 and an E3 are shown here on the board as well, 344 344 00:13:01,800 --> 00:13:04,200 and both of those are European standards. 345 345 00:13:04,200 --> 00:13:06,600 It's two megabits connection for an E1, 346 346 00:13:06,600 --> 00:13:09,600 and 34 megabit connection for an E3. 347 347 00:13:09,600 --> 00:13:12,248 The last two we have are both fiber networks. 348 348 00:13:12,248 --> 00:13:16,427 ATM, which can be anywhere from an OC-3 up to an OC-12, 349 349 00:13:16,427 --> 00:13:19,380 and SONET, which can use anything from an OC-1, 350 350 00:13:19,380 --> 00:13:22,640 all the way up to an OC-3072, 351 351 00:13:22,640 --> 00:13:25,540 which is 160 gigabits per second, 352 352 00:13:25,540 --> 00:13:27,450 which is really quite fast. 353 353 00:13:27,450 --> 00:13:28,590 Now, do you have to memorize 354 354 00:13:28,590 --> 00:13:29,910 all the decimal points like this, 355 355 00:13:29,910 --> 00:13:33,080 the 1.544 for a T1 and things like that? 356 356 00:13:33,080 --> 00:13:34,880 As I said before, no. 357 357 00:13:34,880 --> 00:13:37,340 Remember, this is a multiple choice exam. 358 358 00:13:37,340 --> 00:13:38,940 If you see one that looks close, 359 359 00:13:38,940 --> 00:13:40,480 that's going to be the right answer. 360 360 00:13:40,480 --> 00:13:41,860 So put this in your notes, 361 361 00:13:41,860 --> 00:13:43,890 look it over a couple of times before test day, 362 362 00:13:43,890 --> 00:13:45,100 and you should do just fine 363 363 00:13:45,100 --> 00:13:47,150 when you get these questions on the exam.