1 00:00:00,090 --> 00:00:00,960 In this lesson, 2 00:00:00,960 --> 00:00:03,180 we're going to talk about VoIP issues. 3 00:00:03,180 --> 00:00:06,270 Now, VoIP stands for the voiceover internet protocol, 4 00:00:06,270 --> 00:00:08,250 and this is a set of protocols that we use to be able 5 00:00:08,250 --> 00:00:11,490 to send streaming voice and video in real time. 6 00:00:11,490 --> 00:00:15,420 Now, unlike traditional network protocols like HTTP, FTP 7 00:00:15,420 --> 00:00:18,810 or email, when you're dealing with a real-time application, 8 00:00:18,810 --> 00:00:20,340 being able to have a very low latency 9 00:00:20,340 --> 00:00:23,280 and a very high quality of service is imperative 10 00:00:23,280 --> 00:00:24,990 to having a good voice connection 11 00:00:24,990 --> 00:00:27,150 or video connection when using real-time 12 00:00:27,150 --> 00:00:29,250 protocols such as VoIP. 13 00:00:29,250 --> 00:00:31,440 Now, when you're dealing with VoIP services, 14 00:00:31,440 --> 00:00:32,670 traditionally this is used 15 00:00:32,670 --> 00:00:34,920 to make phone calls over the internet. 16 00:00:34,920 --> 00:00:36,750 If you have poor VoIP service, 17 00:00:36,750 --> 00:00:39,570 you're going to have issues like dropouts in the calls, issues 18 00:00:39,570 --> 00:00:41,070 where you hear echoing from the other end 19 00:00:41,070 --> 00:00:44,190 or other kinds of glitches inside of the call. 20 00:00:44,190 --> 00:00:47,040 Now, when you're sending ordinary data over the network, 21 00:00:47,040 --> 00:00:49,110 you can have the packets delivered in any order, 22 00:00:49,110 --> 00:00:51,120 and it can take longer or shorter, 23 00:00:51,120 --> 00:00:52,860 and it really won't make a difference. 24 00:00:52,860 --> 00:00:55,440 But if we're having a phone call, you need to make sure 25 00:00:55,440 --> 00:00:57,000 that the things I'm saying are coming 26 00:00:57,000 --> 00:01:00,210 to you in the proper order and at the proper time, 27 00:01:00,210 --> 00:01:03,660 and this is why real time protocols like VoIP really have 28 00:01:03,660 --> 00:01:06,122 to rely on a high quality of service level. 29 00:01:06,122 --> 00:01:08,820 Now, if you don't have a very good quality of service, 30 00:01:08,820 --> 00:01:11,250 you're going to see that you're going to get two major quality 31 00:01:11,250 --> 00:01:13,950 issues that affect VoIP drastically. 32 00:01:13,950 --> 00:01:16,410 This is known as latency and jitter. 33 00:01:16,410 --> 00:01:18,930 Now, latency is the time it takes for a signal 34 00:01:18,930 --> 00:01:20,610 to reach the intended client, 35 00:01:20,610 --> 00:01:22,710 and this is measured in milliseconds. 36 00:01:22,710 --> 00:01:25,530 Now, in general, milliseconds are very fast. 37 00:01:25,530 --> 00:01:27,270 We're talking about 1/1000th 38 00:01:27,270 --> 00:01:29,430 of a second is one millisecond. 39 00:01:29,430 --> 00:01:31,620 But if we're talking using a VoIP connection 40 00:01:31,620 --> 00:01:35,610 and the latency increases to over 100 to 200 milliseconds, 41 00:01:35,610 --> 00:01:37,440 it's actually going to be noticeable in the 42 00:01:37,440 --> 00:01:39,330 audio when you're listening to me. 43 00:01:39,330 --> 00:01:41,640 For example, if you're using a satellite internet 44 00:01:41,640 --> 00:01:44,010 connection, generally you're going to have somewhere 45 00:01:44,010 --> 00:01:48,060 between 150 to 250 milliseconds added to every single thing 46 00:01:48,060 --> 00:01:50,280 that you send because of the time it takes to go up 47 00:01:50,280 --> 00:01:51,921 to the satellite, down from the satellite, 48 00:01:51,921 --> 00:01:54,480 over across the internet, up to the satellite, 49 00:01:54,480 --> 00:01:57,510 down from the satellite, and be able to send all that data. 50 00:01:57,510 --> 00:02:00,090 Now, because of that, that means you have a higher latency, 51 00:02:00,090 --> 00:02:02,940 and in most applications, this wouldn't be a big deal. 52 00:02:02,940 --> 00:02:04,950 But with VoIP it is. 53 00:02:04,950 --> 00:02:06,357 As you have a higher latency, 54 00:02:06,357 --> 00:02:08,496 that means you may start hearing echoes inside 55 00:02:08,496 --> 00:02:11,160 of your connections and you'll hear your own voice repeated 56 00:02:11,160 --> 00:02:14,040 back to you as you're talking over a VoIP connection. 57 00:02:14,040 --> 00:02:15,660 To be able to minimize this, we need 58 00:02:15,660 --> 00:02:17,790 to ensure the latency stays low. 59 00:02:17,790 --> 00:02:19,650 Generally, to have a high quality of service 60 00:02:19,650 --> 00:02:21,120 when using a VoIP connection, 61 00:02:21,120 --> 00:02:23,880 you want to make sure you keep your latency under about 50 62 00:02:23,880 --> 00:02:25,620 to 100 milliseconds. 63 00:02:25,620 --> 00:02:27,270 I can tell you from personal experience, 64 00:02:27,270 --> 00:02:29,760 when I was using VoIP over a satellite connection 65 00:02:29,760 --> 00:02:32,430 that was using a satellite out in geosynchronous orbit, 66 00:02:32,430 --> 00:02:35,280 it was about a 500 millisecond round trip. 67 00:02:35,280 --> 00:02:37,770 Now, because of that, once I said something, I would have 68 00:02:37,770 --> 00:02:39,300 to wait about half a second 69 00:02:39,300 --> 00:02:41,850 before the other person heard it, said something back, 70 00:02:41,850 --> 00:02:43,350 and then I would receive that. 71 00:02:43,350 --> 00:02:45,990 So we always had this delay in our conversation, 72 00:02:45,990 --> 00:02:48,840 and it got to the point when we had significant latency up 73 00:02:48,840 --> 00:02:51,810 to about 1000 milliseconds where I basically have to say 74 00:02:51,810 --> 00:02:53,580 what I was going to say and then use some kind 75 00:02:53,580 --> 00:02:56,400 of a keyword like "Over," so they knew that I was done in 76 00:02:56,400 --> 00:02:58,860 that sentence and it was safe for them to start talking. 77 00:02:58,860 --> 00:03:01,530 This a really unpleasant experience if you're using VoIP 78 00:03:01,530 --> 00:03:03,270 over a high latency connection, 79 00:03:03,270 --> 00:03:05,370 but in some cases you just don't have a choice 80 00:03:05,370 --> 00:03:06,360 because you're dealing with something 81 00:03:06,360 --> 00:03:08,130 like a satellite connection. 82 00:03:08,130 --> 00:03:09,570 The second issue you may experience 83 00:03:09,570 --> 00:03:11,940 with VoIP is what's known as jitter. 84 00:03:11,940 --> 00:03:13,440 Now, jitter is a measurement 85 00:03:13,440 --> 00:03:15,471 of the variation in delay over time, 86 00:03:15,471 --> 00:03:17,880 and it's measured by sampling the elapsed time 87 00:03:17,880 --> 00:03:19,590 between when the packets are arriving 88 00:03:19,590 --> 00:03:21,450 and when they were originally sent. 89 00:03:21,450 --> 00:03:24,420 Now, in general, most VoIP services are going to send their 90 00:03:24,420 --> 00:03:26,820 data over a UDP connection. 91 00:03:26,820 --> 00:03:29,760 Because of this, that data can arrive in any order 92 00:03:29,760 --> 00:03:30,990 as it crosses the network, 93 00:03:30,990 --> 00:03:32,250 and then the system tries to put it 94 00:03:32,250 --> 00:03:33,780 back into the correct order. 95 00:03:33,780 --> 00:03:36,630 So as your latency increases up around 30 96 00:03:36,630 --> 00:03:38,010 to 50 milliseconds, 97 00:03:38,010 --> 00:03:40,650 you're going to start having impacts on your call quality 98 00:03:40,650 --> 00:03:42,540 and you're going to start hearing jitter. 99 00:03:42,540 --> 00:03:45,120 Now, jitter can happen because of a high latency environment 100 00:03:45,120 --> 00:03:47,850 or because your packets are taking different routes across 101 00:03:47,850 --> 00:03:50,760 the internet and being reassembled in the incorrect order 102 00:03:50,760 --> 00:03:53,160 because we're dealing with a real-time protocol. 103 00:03:53,160 --> 00:03:55,380 For example, if I started talking to you 104 00:03:55,380 --> 00:03:57,420 and instead of saying, "One, two, three," 105 00:03:57,420 --> 00:04:00,750 you heard those packets as "One, three, two," that means 106 00:04:00,750 --> 00:04:03,300 that packet three got there before packet two. 107 00:04:03,300 --> 00:04:05,857 Now generally, you're not going to hear the entire word like 108 00:04:05,857 --> 00:04:08,040 "One, two, and three," in the wrong order, 109 00:04:08,040 --> 00:04:10,080 but instead just pieces of the word. 110 00:04:10,080 --> 00:04:12,570 And this is why you'll hear almost like a robotic static 111 00:04:12,570 --> 00:04:14,963 inside of a VoIP conversation if you have a low 112 00:04:14,963 --> 00:04:16,860 quality of service. 113 00:04:16,860 --> 00:04:19,709 So how do you solve latency and jitter? 114 00:04:19,709 --> 00:04:21,480 Well, there's two ways to do it. 115 00:04:21,480 --> 00:04:23,458 First, you can increase the performance overall 116 00:04:23,458 --> 00:04:25,260 of the entire network. 117 00:04:25,260 --> 00:04:26,550 Now, that's pretty hard to do 118 00:04:26,550 --> 00:04:28,470 because you have to consider every single piece 119 00:04:28,470 --> 00:04:31,170 of the network from that VoIP handset all the way 120 00:04:31,170 --> 00:04:33,720 through the network and your WAN connection. 121 00:04:33,720 --> 00:04:35,070 The second thing you can do though, 122 00:04:35,070 --> 00:04:37,500 is you can implement quality of service. 123 00:04:37,500 --> 00:04:39,720 Now, quality of service is an important tool 124 00:04:39,720 --> 00:04:41,220 inside of your network. 125 00:04:41,220 --> 00:04:42,750 This is a mechanism that allows you 126 00:04:42,750 --> 00:04:45,840 to prioritize certain traffic over others. 127 00:04:45,840 --> 00:04:48,960 For example, in your small office home office network, 128 00:04:48,960 --> 00:04:50,520 you can actually configure your devices 129 00:04:50,520 --> 00:04:52,290 to prioritize your VoIP traffic 130 00:04:52,290 --> 00:04:55,170 and make it the highest priority in your network. 131 00:04:55,170 --> 00:04:57,540 Now, in most small office home office environments, 132 00:04:57,540 --> 00:04:59,340 that would be a very true statement. 133 00:04:59,340 --> 00:05:01,500 Your voice traffic should be the most important 134 00:05:01,500 --> 00:05:04,560 because it is the most susceptible to high latency 135 00:05:04,560 --> 00:05:07,680 and this effective jitter when packets arrive out of order. 136 00:05:07,680 --> 00:05:09,510 So by configuring your network devices 137 00:05:09,510 --> 00:05:12,240 to identify those Voice over IP packets, 138 00:05:12,240 --> 00:05:14,610 you can prioritize those over everything else in your 139 00:05:14,610 --> 00:05:17,310 network, and this will reduce your latency and your jitter 140 00:05:17,310 --> 00:05:20,070 and give you a higher quality of service to your end user. 141 00:05:20,070 --> 00:05:22,380 Now keep in mind the settings you set for quality 142 00:05:22,380 --> 00:05:25,560 of service only affect things inside of your network. 143 00:05:25,560 --> 00:05:27,930 Once it gets to a public network like the internet, 144 00:05:27,930 --> 00:05:30,180 your quality of service rules no longer are going to be 145 00:05:30,180 --> 00:05:31,830 applied, and then it's up to each 146 00:05:31,830 --> 00:05:34,170 of those internet service providers across the internet on 147 00:05:34,170 --> 00:05:36,810 whether or not they're going to prioritize your VoIP traffic 148 00:05:36,810 --> 00:05:38,700 over other things that they're sending to be able 149 00:05:38,700 --> 00:05:40,560 to give you that higher quality of service. 150 00:05:40,560 --> 00:05:43,290 That said, it's still important to set up QoS 151 00:05:43,290 --> 00:05:45,570 or quality of service inside of your own network 152 00:05:45,570 --> 00:05:47,040 for your VoIP devices 153 00:05:47,040 --> 00:05:48,930 because this will allow you to prioritize it inside 154 00:05:48,930 --> 00:05:51,180 of your own network and at least get it a headstart 155 00:05:51,180 --> 00:05:52,902 out and onto the internet. 156 00:05:52,902 --> 00:05:55,830 So remember, when it comes to VoIP issues, 157 00:05:55,830 --> 00:05:58,320 the two biggest issues you're going to experience are high 158 00:05:58,320 --> 00:05:59,760 latency and jitter. 159 00:05:59,760 --> 00:06:02,220 And the best way to solve these is by implementing a quality 160 00:06:02,220 --> 00:06:04,260 of service policy inside of your own network 161 00:06:04,260 --> 00:06:06,003 to prioritize your VoIP traffic.