1 00:00:01,290 --> 00:00:10,400 Now unlike FedEx or DHL we're not sending physical packages between network devices we're sending packets. 2 00:00:10,980 --> 00:00:17,860 So how does a phone indicate to a switch that its traffic is of great importance. 3 00:00:17,970 --> 00:00:24,040 And how does one switch indicate to another switch that some packets are more important than others. 4 00:00:24,090 --> 00:00:31,020 So this is called classification and marking a phone would classify its own traffic as being important 5 00:00:31,320 --> 00:00:36,470 but the traffic from a P.C. would be classified as not being important. 6 00:00:36,480 --> 00:00:43,080 A switch can be configured with access lists or it could use other technologies such as Anbar or network 7 00:00:43,080 --> 00:00:51,660 based application recognition to recognize certain applications such as HDP or voice traffic or video 8 00:00:51,660 --> 00:00:55,320 traffic and then pro tries that traffic accordingly. 9 00:00:55,320 --> 00:01:03,570 So essentially a phone sees its own traffic as important but not the traffic of a P.C. a switch or a 10 00:01:03,570 --> 00:01:09,600 router has many options that you can use to put traffic into classes. 11 00:01:09,600 --> 00:01:16,200 Again you could use an access list or network based application recognition but once you've put your 12 00:01:16,200 --> 00:01:20,660 traffic into a class so as an example the phone says its traffic is important. 13 00:01:20,700 --> 00:01:22,110 It's voice traffic. 14 00:01:22,350 --> 00:01:26,850 It needs to mark the traffic and send it to the first switch. 15 00:01:26,850 --> 00:01:32,040 So all packets are sent from the phone to the switch need to be marked as important. 16 00:01:32,040 --> 00:01:39,210 Now that can be done at a layer to using editor at 1 Q So on Ethernet we would require attitude at one 17 00:01:39,210 --> 00:01:46,650 Q links and in the editor to one Q header we can change what's called the Cost field or plus of service 18 00:01:46,650 --> 00:01:54,810 field to indicate the importance of the traffic that is known as 82 two to one P or edited to 1 priority 19 00:01:54,810 --> 00:02:02,310 but we could also use MPEG less experimental bits to indicate that the traffic is important at least 20 00:02:02,330 --> 00:02:10,470 three in the IP header we've got IP precedents and differentiated services code points or DCP IP explicit 21 00:02:10,470 --> 00:02:17,210 congestion notification or ECM can also be used but that's not covered in the CCN a course the layer 22 00:02:17,240 --> 00:02:22,660 two and layer three parameters are the ones that you should concentrate on for the CCMA exam so layer 23 00:02:22,760 --> 00:02:29,780 two we have added to the one Q or editor the one PE class of service but there are three bits in the 24 00:02:29,780 --> 00:02:35,490 header which equate it to eight classes of service in the range 0 to 7. 25 00:02:35,780 --> 00:02:37,730 So let's look at that practically. 26 00:02:37,730 --> 00:02:42,590 I'm gonna capture traffic on this link between the phone and the switch 27 00:02:46,240 --> 00:02:47,890 so why shock is capturing traffic 28 00:02:52,470 --> 00:02:57,330 now this phone icon is actually in austere not a node which is a packet generator 29 00:03:00,400 --> 00:03:08,190 in the packet a generator I can specify the protein bits of an attitude at one Q header. 30 00:03:08,560 --> 00:03:17,180 Notice the values of from 0 to 7 because this is a phone I'm going to set the priority to 5 click okay 31 00:03:17,690 --> 00:03:22,400 and then I'm going to start generating packets of packets of being sent into the network. 32 00:03:22,400 --> 00:03:33,060 These are UDP packets that I'm sending so here's one of the packets that have been generated and notice 33 00:03:33,070 --> 00:03:39,540 that Ethernet to we have a source and destination MAC Address we are generating an attitude at one Q 34 00:03:39,540 --> 00:03:42,500 frame and in the edit to the one Q frame. 35 00:03:42,510 --> 00:03:50,250 Notice we've got a priority field so the priority field or cost field consists of three binary bits 36 00:03:50,730 --> 00:03:54,930 in the range 0 0 0 up to 1 1 1. 37 00:03:54,930 --> 00:04:02,310 In other words in the range 0 2 7 there are eight binary values that we can configure and in this case 38 00:04:02,320 --> 00:04:06,600 offset the value to five to indicate voice traffic. 39 00:04:06,980 --> 00:04:16,780 So back in Austin Noto I'll change the cost value to seven and what I'll do is generate more frames. 40 00:04:17,060 --> 00:04:20,730 So scrolling down to the latest frames. 41 00:04:20,800 --> 00:04:29,290 Notice the party but is three binary ones which equates to network control in this case a filter for 42 00:04:29,290 --> 00:04:34,890 UDP in the previous frame it showed up as video. 43 00:04:34,920 --> 00:04:37,940 In other words we require low latency and jitter. 44 00:04:38,010 --> 00:04:46,420 Now that's used by Cisco phones to indicate important voice traffic the SRM D guide has some recommendations 45 00:04:46,420 --> 00:04:55,000 for what you should mock traffic as so act layer to causal NPL is experimental but a course of five 46 00:04:55,360 --> 00:05:02,940 is what she used for voice video Cisco recommend using a cost value for mission critical data should 47 00:05:02,940 --> 00:05:08,190 have a cost value of three calls signaling to set up telephone calls should have a cost value of three 48 00:05:09,060 --> 00:05:14,020 and then it goes all the way down to best effort which has a cost value of zero. 49 00:05:14,220 --> 00:05:22,770 So as an example if we were sending calls signaling something like SAP or a should 3 the car's value 50 00:05:22,770 --> 00:05:24,820 should be set to 3. 51 00:05:24,900 --> 00:05:32,340 So we should set the course value here to 3 and generate some frames. 52 00:05:32,660 --> 00:05:40,230 And it is over here that cost value is set to three binary 0 1 1 decimal is 3. 53 00:05:40,260 --> 00:05:45,790 Now applications should follow the conventions but sometimes they don't. 54 00:05:45,890 --> 00:05:49,040 And this is where the trust boundary is important. 55 00:05:49,040 --> 00:05:54,440 Would you trust your users to set their quality of service correctly. 56 00:05:54,440 --> 00:06:01,080 Typically not in this case the switch can trust the markings that it receives from the phone but not 57 00:06:01,080 --> 00:06:04,560 necessarily the markings that it receives from this P.C.. 58 00:06:05,220 --> 00:06:07,480 So again they are different ways to mock. 59 00:06:07,590 --> 00:06:12,650 We can market layer two in Ethernet frames using an editor the one Q header. 60 00:06:12,840 --> 00:06:18,370 As I've demonstrated there are eight classes in the range 0 to 7. 61 00:06:18,450 --> 00:06:27,270 We can also mark type of service which is at least three so in the type of service header. 62 00:06:27,510 --> 00:06:33,900 There are eight binary bits and in the old days we used to have what is called IP precedents which marked 63 00:06:34,110 --> 00:06:36,650 the most significant three bits. 64 00:06:36,660 --> 00:06:43,140 Today we use differentiated services code points or serve bits which is a marking of the most significant 65 00:06:43,230 --> 00:06:44,650 six bits. 66 00:06:44,670 --> 00:06:51,690 I'll talk about this in more detail in a moment but just to demonstrate it what we could do is under 67 00:06:51,690 --> 00:07:03,370 the IP header we can set a type of service or DCP Valley so if we send a frame into the network notice 68 00:07:03,370 --> 00:07:09,430 at least two we have the editor of one Q header set to a cost value of 3. 69 00:07:09,730 --> 00:07:18,250 But at least 3 we have a differentiated services code point set in this example to expedited forwarding 70 00:07:18,700 --> 00:07:20,040 or 46. 71 00:07:20,200 --> 00:07:28,570 So we've marked one two three four five six but in the IP header explicit congestion notification the 72 00:07:28,570 --> 00:07:35,740 last 2 bits here are not used and you don't need to know ECM for the CCMA exam but notice the type of 73 00:07:35,740 --> 00:07:44,200 service field in the IP for header is 8 but since size IP precedence uses the most significant three 74 00:07:44,200 --> 00:07:49,510 bits differentiated services code points uses the most significant six bits. 75 00:07:49,610 --> 00:07:55,410 ESPN uses the least significant two bits and that's what we can see here. 76 00:07:55,420 --> 00:08:00,300 Here's an example of DCP and ESPN. 77 00:08:00,310 --> 00:08:02,570 Notice this is just a standard IP packet. 78 00:08:02,590 --> 00:08:05,990 We have source address destination address. 79 00:08:06,130 --> 00:08:13,660 We have the protocol being UDP but one of the fields is the tops field or type of service field which 80 00:08:13,660 --> 00:08:16,360 consists of DCP and ECM. 81 00:08:16,360 --> 00:08:16,840 Today.