1 1 00:00:00,590 --> 00:00:03,560 Why do we need quality of service or QoS? 2 2 00:00:03,560 --> 00:00:06,530 Well, nowadays we operate converge networks, 3 3 00:00:06,530 --> 00:00:09,380 which means all of our networks are carrying voice, data 4 4 00:00:09,380 --> 00:00:11,970 and video content over the same wire. 5 5 00:00:11,970 --> 00:00:14,260 We don't have them all separate out like we used to. 6 6 00:00:14,260 --> 00:00:16,900 We used to have networks for phones and ones for data 7 7 00:00:16,900 --> 00:00:18,040 and ones for video, 8 8 00:00:18,040 --> 00:00:21,840 but now everything's riding over the same IP networks. 9 9 00:00:21,840 --> 00:00:24,650 So, because of this convergence of mediums, 10 10 00:00:24,650 --> 00:00:25,670 we have these networks 11 11 00:00:25,670 --> 00:00:27,970 that now have a high level availability 12 12 00:00:27,970 --> 00:00:29,340 to ensure proper delivery 13 13 00:00:29,340 --> 00:00:31,190 over all of these different medians, 14 14 00:00:31,190 --> 00:00:32,460 because we want a phone to work 15 15 00:00:32,460 --> 00:00:34,430 every time we pick up the phone, right? 16 16 00:00:34,430 --> 00:00:37,460 Well, by using QoS, we can optimize our network 17 17 00:00:37,460 --> 00:00:40,520 to efficiently utilize all the bandwidth at the right time 18 18 00:00:40,520 --> 00:00:42,400 to deliver the right service to our users 19 19 00:00:42,400 --> 00:00:45,040 and give a success and cost savings. 20 20 00:00:45,040 --> 00:00:47,260 Now, we want to have an excellent quality of service, 21 21 00:00:47,260 --> 00:00:49,090 an excellent service for our customers, 22 22 00:00:49,090 --> 00:00:52,160 and that's what we're going to start doing by using QoS. 23 23 00:00:52,160 --> 00:00:54,640 So what exactly is QoS? 24 24 00:00:54,640 --> 00:00:56,440 Well, quality of service enables us 25 25 00:00:56,440 --> 00:00:59,050 to strategically optimize our network performance 26 26 00:00:59,050 --> 00:01:01,090 based on different types of traffic. 27 27 00:01:01,090 --> 00:01:03,020 Previously, we talked about the fact 28 28 00:01:03,020 --> 00:01:05,570 that we want to categorize our different traffic types. 29 29 00:01:05,570 --> 00:01:08,890 I might have web traffic and voice traffic and video traffic 30 30 00:01:08,890 --> 00:01:10,060 and email traffic. 31 31 00:01:10,060 --> 00:01:11,380 And by categorizing it 32 32 00:01:11,380 --> 00:01:13,660 and identifying these different types of traffic, 33 33 00:01:13,660 --> 00:01:17,120 I can then prioritize that traffic and route it differently. 34 34 00:01:17,120 --> 00:01:19,540 So I might determine how much bandwidth is required 35 35 00:01:19,540 --> 00:01:21,120 for each of those types of traffic. 36 36 00:01:21,120 --> 00:01:23,830 And I can efficiently use my wide area network links 37 37 00:01:23,830 --> 00:01:27,070 and all that bandwidth available, for maximum utilization, 38 38 00:01:27,070 --> 00:01:29,660 and save me bandwidth costs over time. 39 39 00:01:29,660 --> 00:01:31,560 This can help me identify 40 40 00:01:31,560 --> 00:01:32,490 the types of traffic that I should drop 41 41 00:01:32,490 --> 00:01:34,390 whenever there's going to be some kind of congestion, 42 42 00:01:34,390 --> 00:01:35,960 because if you look at the average load, 43 43 00:01:35,960 --> 00:01:38,480 there's always going to be some peaks and some valleys. 44 44 00:01:38,480 --> 00:01:40,440 And so we want to be able to figure that out. 45 45 00:01:40,440 --> 00:01:41,770 So for example, here on the screen, 46 46 00:01:41,770 --> 00:01:44,130 you can see the peaks and the valleys. 47 47 00:01:44,130 --> 00:01:45,370 The peaks over time, 48 48 00:01:45,370 --> 00:01:46,950 and we need to be able to categorize things 49 49 00:01:46,950 --> 00:01:49,150 to fit within our bandwidth limitations. 50 50 00:01:49,150 --> 00:01:51,320 So for example, if we have things like VoIP, 51 51 00:01:51,320 --> 00:01:53,800 or voice over IP, or video service, 52 52 00:01:53,800 --> 00:01:55,400 they need to have a higher priority, 53 53 00:01:55,400 --> 00:01:57,150 because if I'm talking to you on a phone, 54 54 00:01:57,150 --> 00:01:59,150 I don't want a high amount of latency. 55 55 00:01:59,150 --> 00:02:01,320 From checking my bank balance, for instance, though, 56 56 00:02:01,320 --> 00:02:04,190 I can wait another half a second for the web page to load. 57 57 00:02:04,190 --> 00:02:06,770 From listening to you talk, that half a second delay 58 58 00:02:06,770 --> 00:02:08,140 starts sending like an echo, 59 59 00:02:08,140 --> 00:02:10,090 and it gives me a horrible service level. 60 60 00:02:10,090 --> 00:02:11,810 So we want to be able to solve that, 61 61 00:02:11,810 --> 00:02:14,610 and to do that, we use quality of service. 62 62 00:02:14,610 --> 00:02:17,330 Now there are different categories of quality of service. 63 63 00:02:17,330 --> 00:02:21,190 There are three big ones known as delay, jitter and drops. 64 64 00:02:21,190 --> 00:02:22,600 When I talk about delay, 65 65 00:02:22,600 --> 00:02:24,430 this happens when you look at the time 66 66 00:02:24,430 --> 00:02:27,510 that a packet travels from the source to the destination, 67 67 00:02:27,510 --> 00:02:29,300 this is measured in milliseconds, 68 68 00:02:29,300 --> 00:02:31,760 and it's not a big deal if you're dealing with data traffic, 69 69 00:02:31,760 --> 00:02:33,860 but if you're dealing with voice or video, 70 70 00:02:33,860 --> 00:02:35,870 delay is an especially big thing, 71 71 00:02:35,870 --> 00:02:38,110 especially if you're doing things live, 72 72 00:02:38,110 --> 00:02:40,330 like talking on the phone or doing a live stream, 73 73 00:02:40,330 --> 00:02:42,000 or something like that. 74 74 00:02:42,000 --> 00:02:44,970 Now, jitter is an uneven arrival of packets, 75 75 00:02:44,970 --> 00:02:47,800 and this is especially bad in voiceover IP traffic, 76 76 00:02:47,800 --> 00:02:49,640 because you're using something like UDP. 77 77 00:02:49,640 --> 00:02:52,800 And so if I sing something to you, like, "my name is Jason," 78 78 00:02:52,800 --> 00:02:54,840 and you got "Jason my name is," 79 79 00:02:54,840 --> 00:02:56,530 it sounds kind of weird, right? 80 80 00:02:56,530 --> 00:02:58,490 Now, usually it's not big chunks like that, 81 81 00:02:58,490 --> 00:02:59,890 but instead it's little bits 82 82 00:02:59,890 --> 00:03:01,990 and you'll hear these glick and glock sounds 83 83 00:03:01,990 --> 00:03:04,610 that make it jumble up because of that jitter. 84 84 00:03:04,610 --> 00:03:07,350 And this really sounds bad, and it's a bad user experience 85 85 00:03:07,350 --> 00:03:09,130 if you're using voiceover IP. 86 86 00:03:09,130 --> 00:03:10,980 And so jitter is a really bad thing 87 87 00:03:10,980 --> 00:03:12,940 when you're dealing with voice and video. 88 88 00:03:12,940 --> 00:03:15,630 Now, the third thing we have is what's known as a drop. 89 89 00:03:15,630 --> 00:03:18,350 Drops are going to occur during network congestion. 90 90 00:03:18,350 --> 00:03:20,180 When the network becomes too congested, 91 91 00:03:20,180 --> 00:03:22,260 the router simply can't keep up with demand, 92 92 00:03:22,260 --> 00:03:23,860 and the queue starts overflowing, 93 93 00:03:23,860 --> 00:03:25,710 and it'll start dropping packets. 94 94 00:03:25,710 --> 00:03:27,630 This is the way it deals with packet loss, 95 95 00:03:27,630 --> 00:03:30,530 and if you're using TCP, it'll just send it again. 96 96 00:03:30,530 --> 00:03:33,950 But again, if I'm dealing with VoIP, VoIP is usually UDP. 97 97 00:03:33,950 --> 00:03:34,890 And so if we're talking 98 98 00:03:34,890 --> 00:03:36,760 and all of a sudden my voice cuts out like that, 99 99 00:03:36,760 --> 00:03:38,100 that would be bad too. 100 100 00:03:38,100 --> 00:03:41,140 That's why we don't want to have packet drop on a VoIP call. 101 101 00:03:41,140 --> 00:03:43,400 And so we want to make sure that that doesn't happen. 102 102 00:03:43,400 --> 00:03:45,720 These network drops are something that can be avoided 103 103 00:03:45,720 --> 00:03:48,470 by doing the proper quality of service as well. 104 104 00:03:48,470 --> 00:03:49,620 So when we deal with this, 105 105 00:03:49,620 --> 00:03:52,170 we have to think about effective bandwidth. 106 106 00:03:52,170 --> 00:03:53,630 What is our effective bandwidth? 107 107 00:03:53,630 --> 00:03:55,260 This is an important concept. 108 108 00:03:55,260 --> 00:03:57,360 So let's look at this client and this server. 109 109 00:03:57,360 --> 00:03:59,100 There's probably a lot more to this network 110 110 00:03:59,100 --> 00:04:00,410 than what I'm showing you here on the screen, 111 111 00:04:00,410 --> 00:04:02,960 but I've simplified it down for this example. 112 112 00:04:02,960 --> 00:04:04,880 Here, you can see I have my client on the left, 113 113 00:04:04,880 --> 00:04:06,580 and he wants to talk to the server. 114 114 00:04:06,580 --> 00:04:07,940 So he goes up through the switch, 115 115 00:04:07,940 --> 00:04:10,850 which uses 100 megabit per second Cat-5 cable. 116 116 00:04:10,850 --> 00:04:12,280 Then he goes through a WAN link 117 117 00:04:12,280 --> 00:04:15,050 over a 256 kilobit per second connection 118 118 00:04:15,050 --> 00:04:17,240 because he's using an old DSL line. 119 119 00:04:17,240 --> 00:04:20,830 Then that connects from that ISP over a T1 connection 120 120 00:04:20,830 --> 00:04:22,130 to another router. 121 121 00:04:22,130 --> 00:04:25,580 That router connects to an E1 connection to another router. 122 122 00:04:25,580 --> 00:04:27,900 And from that router, it goes down a WAN link 123 123 00:04:27,900 --> 00:04:30,510 over a 512 kilobit per second connection, 124 124 00:04:30,510 --> 00:04:33,490 and then down to a switch with a gigabit connection, 125 125 00:04:33,490 --> 00:04:34,810 down to the server. 126 126 00:04:34,810 --> 00:04:37,460 Now, what is my effective bandwidth? 127 127 00:04:37,460 --> 00:04:40,370 Well, it's 256 kilobits per second, 128 128 00:04:40,370 --> 00:04:42,930 because no matter how fast any of the other links are, 129 129 00:04:42,930 --> 00:04:45,600 whatever the lowest link is inside of this connection, 130 130 00:04:45,600 --> 00:04:47,720 that is going to be your effective bandwidth. 131 131 00:04:47,720 --> 00:04:49,680 So we talked about quality of service categories, 132 132 00:04:49,680 --> 00:04:51,560 in our next lesson, we're going to be talking about 133 133 00:04:51,560 --> 00:04:53,280 how we can alleviate this problem 134 134 00:04:53,280 --> 00:04:56,280 of this effective bandwidth, and try to get more out of it, 135 135 00:04:56,280 --> 00:04:57,113 because we need to be able 136 136 00:04:57,113 --> 00:05:00,370 to increase our available bandwidth, but in this example, 137 137 00:05:00,370 --> 00:05:02,620 we're limited to 256 kilobits, 138 138 00:05:02,620 --> 00:05:05,100 which is going to be really, really slow for us. 139 139 00:05:05,100 --> 00:05:07,070 Now, I like to think about effective bandwidth 140 140 00:05:07,070 --> 00:05:08,810 like water flowing through pipes. 141 141 00:05:08,810 --> 00:05:11,090 I can have big pipes and I can have little pipes. 142 142 00:05:11,090 --> 00:05:12,170 And if I have little pipes, 143 143 00:05:12,170 --> 00:05:14,250 I'm going to get less water per second through it 144 144 00:05:14,250 --> 00:05:15,950 than if I have a really big pipe. 145 145 00:05:15,950 --> 00:05:18,210 And so this is the idea, if you think about a big funnel, 146 146 00:05:18,210 --> 00:05:20,430 it can start to back up on us, right? 147 147 00:05:20,430 --> 00:05:21,370 That's the concept, 148 148 00:05:21,370 --> 00:05:23,140 And we have to figure out how we can fix that 149 149 00:05:23,140 --> 00:05:25,140 by using quality of service effectively, 150 150 00:05:25,140 --> 00:05:27,590 which we're going to discuss more in the next video.