1
00:00:00,300 --> 00:00:02,880
Now voice is very different to data.

2
00:00:03,000 --> 00:00:10,260
Voice calls are smooth in that they require a certain amount of bandwidth and they require that all

3
00:00:10,260 --> 00:00:11,130
the time.

4
00:00:11,370 --> 00:00:14,670
They don't burst like a data application's do.

5
00:00:14,790 --> 00:00:22,290
Voice codecs such as G 7 to 9 or G 711 use a certain amount of bandwidth and they need that for the

6
00:00:22,290 --> 00:00:23,670
entire voice call.

7
00:00:23,940 --> 00:00:26,540
So they said to be smooth, they benign.

8
00:00:26,550 --> 00:00:32,310
They don't try and grab bandwidth from other applications, but they are very drop sensitive and very

9
00:00:32,310 --> 00:00:33,480
delay sensitive.

10
00:00:33,510 --> 00:00:38,690
If your voice packets are dropped or delayed, it will affect the voice conversation.

11
00:00:38,700 --> 00:00:45,990
So in a voice over IP scenario, it's very important that packets arrive without a lot of delay and

12
00:00:45,990 --> 00:00:47,670
packets are not dropped.

13
00:00:48,150 --> 00:00:54,600
Voice is transmitted across UDP, so there's no capability to retransmit loss to voice.

14
00:00:54,720 --> 00:00:57,840
These are the one way requirements for voice latency.

15
00:00:57,840 --> 00:01:05,349
Less than 150 milliseconds jitter less than 30 milliseconds lost less than 1% bandwidth.

16
00:01:05,349 --> 00:01:11,040
It does vary depending on the codec used, but as an example, it's in the range 30 kilobits per second,

17
00:01:11,040 --> 00:01:13,380
228 kilobits per second.

18
00:01:14,280 --> 00:01:20,700
Video has characteristics of voice and characteristics of data in that it's bursty and greedy.

19
00:01:21,420 --> 00:01:28,110
A video with a lot of movement requires more bandwidth than a video where there's not a lot of movement.

20
00:01:28,680 --> 00:01:36,060
So as an example, if you were watching a video stream where there's a lot of action on the screen so

21
00:01:36,060 --> 00:01:42,570
people are moving around or cause a racing or an ultimate example would be a video of a fire.

22
00:01:42,630 --> 00:01:46,260
There's a lot of changes on the screen when videoing fire.

23
00:01:46,410 --> 00:01:49,290
It's going to grab a lot of bandwidth and be very bursty.

24
00:01:49,650 --> 00:01:55,800
If you were videoing a stall scene, so as an example, you were videoing a wall on a building with

25
00:01:55,800 --> 00:01:59,460
no movement, the bandwidth requirements would be a lot less.

26
00:01:59,880 --> 00:02:02,910
Video, however, is drop sensitive like voice.

27
00:02:02,910 --> 00:02:08,090
It's delay sensitive like voice and it uses UDP rather than TCP.

28
00:02:08,580 --> 00:02:16,560
So the one way requirements for video are similar to voice delay or latency less than 150 milliseconds

29
00:02:16,560 --> 00:02:22,020
jitter less than 30 milliseconds lost between 0.1 and 1%.

30
00:02:22,410 --> 00:02:25,510
Bandwidth does vary depending on the video stream.

31
00:02:25,530 --> 00:02:32,610
As an example, if you're watching 720 PE or 180 PE or high definition, the bandwidth requirements

32
00:02:32,610 --> 00:02:33,810
can be a lot higher.

33
00:02:34,140 --> 00:02:42,060
But for the CNA will use a value of 384 kilobits per second to 20 plus megabits per second.

34
00:02:42,060 --> 00:02:46,890
So the thing to remember is that video and voice or delay sensitive.

35
00:02:46,980 --> 00:02:48,900
They are drop sensitive.

36
00:02:48,930 --> 00:02:52,140
A lot of data traffic doesn't have those requirements.

37
00:02:52,260 --> 00:02:58,920
So data traffic such as FTP can be dropped, it can be delayed, but voice traffic in a audio stream

38
00:02:58,950 --> 00:03:03,330
or a video conference needs to be prioritized.

39
00:03:03,930 --> 00:03:09,960
So the idea with quality of service is that we're going to give priority to some sessions over other

40
00:03:09,960 --> 00:03:10,770
sessions.

41
00:03:10,890 --> 00:03:17,280
The packets of delay sensitive applications such as voice and video are going to be prioritized over

42
00:03:17,280 --> 00:03:21,210
traffic from non delay sensitive applications such as FTP.

43
00:03:21,240 --> 00:03:26,200
We'll drop FTP packets before we drop voice packets with FTP.

44
00:03:26,220 --> 00:03:27,030
It doesn't matter.

45
00:03:27,030 --> 00:03:28,680
It will retransmit.

46
00:03:28,860 --> 00:03:34,110
But if we did drop voice packets and video packets, it would affect the user experience.

47
00:03:34,350 --> 00:03:40,530
So with quality of service, we are going to create policies and implement policies using quality of

48
00:03:40,530 --> 00:03:47,730
service mechanisms on a network to prioritize certain traffic types over other traffic types.