1 00:00:04,850 --> 00:00:11,250 So again protocol at Layer 4 is TTP which Layer 7 protocol is used. 2 00:00:11,390 --> 00:00:16,100 Notice destination port is 80 80 is HDP. 3 00:00:17,220 --> 00:00:29,150 Notice we've got what's called a destination port we could search in Google for port numbers and let's 4 00:00:29,150 --> 00:00:38,800 go to the eye on a Web site which is the Internet Assigned Numbers Authority and if we search for 80 5 00:00:39,100 --> 00:00:45,440 in that list you can see that HP port 80 is world wide web. 6 00:00:45,490 --> 00:00:48,810 A GDP. 7 00:00:48,870 --> 00:00:56,400 Now some protocols such as DNS or domain name server or domain name system as it's sometimes called 8 00:00:57,120 --> 00:01:04,350 uses both DCP and UDP HDP generally uses TTP because we want reliability. 9 00:01:04,350 --> 00:01:14,160 So again Layer 3 protocol is IP version 4 Layer 4 protocol is TTP we are indicating the application 10 00:01:14,490 --> 00:01:19,110 that we want to send the data to by the port number. 11 00:01:19,110 --> 00:01:24,930 Think of it as follows The server is running multiple services and I want you to see these services 12 00:01:24,930 --> 00:01:27,510 and look at the protocols going to the services. 13 00:01:27,510 --> 00:01:31,080 So under services we've got an HP server. 14 00:01:31,200 --> 00:01:33,330 We've also got a TFT P server. 15 00:01:33,450 --> 00:01:38,850 We've got an FTB server and email server and various other servers. 16 00:01:39,270 --> 00:01:40,940 Where should the data go. 17 00:01:40,950 --> 00:01:43,260 It needs to go to the right application. 18 00:01:43,350 --> 00:01:49,930 You're not going to open up a MP 3 music file in a word processor. 19 00:01:50,010 --> 00:01:51,000 It's not going to work. 20 00:01:51,000 --> 00:01:59,730 Word opens word processing files an application such as a music application gets used to open music 21 00:01:59,730 --> 00:02:00,560 files. 22 00:02:00,660 --> 00:02:05,760 So you need the right application or right service to work with the right data. 23 00:02:05,820 --> 00:02:14,070 So again you use a port number to send the ATP traffic to the HP server you use a port number like 53 24 00:02:14,070 --> 00:02:16,290 to send traffic to a DNS server. 25 00:02:16,380 --> 00:02:25,430 You use Port 21 to send it to FCP server or service sixty nine to a TFT IP service. 26 00:02:25,560 --> 00:02:31,380 You have one physical server running different processes or different applications and you want to send 27 00:02:31,380 --> 00:02:36,420 the data to the correct service or correct server application. 28 00:02:36,480 --> 00:02:40,130 Those applications listen on a specific port number. 29 00:02:40,140 --> 00:02:48,750 So the HDP server listens and port 80 the NDP server will listen on Port 21 TFT people listen on Port 30 00:02:48,750 --> 00:02:50,440 69. 31 00:02:50,510 --> 00:02:58,130 So this is indicating to the server that this data needs to go to the application listening on port 32 00:02:58,130 --> 00:03:01,650 80 and you can see the HBP request. 33 00:03:01,910 --> 00:03:11,030 So packet gets sent to the server the server because it's listening on that port will receive the data 34 00:03:11,270 --> 00:03:13,740 and send it to the relevant application. 35 00:03:13,790 --> 00:03:19,360 What you'll also notice here is the source port is 1025. 36 00:03:19,430 --> 00:03:21,790 So let's talk about port numbers and a bit more detail. 37 00:03:21,800 --> 00:03:29,840 A server service will listen on what's called a well known port number but when you initiate a session 38 00:03:29,840 --> 00:03:38,090 to a well-known port number such as 80 you will use what's called a femoral or random port number. 39 00:03:38,240 --> 00:03:47,460 Now going back to the Iona we told that service names are assigned on a first come first serve basis 40 00:03:47,520 --> 00:03:54,060 as documented in this or if sea service names and port numbers are used to distinguish between services 41 00:03:54,060 --> 00:03:59,420 that run over transport protocols such as TCB UDP and others. 42 00:03:59,490 --> 00:04:00,980 This is the important part. 43 00:04:00,990 --> 00:04:11,640 These port numbers in the range 0 to 1023 are signed as system port numbers so 80 is in that range. 44 00:04:11,640 --> 00:04:16,940 We have what's called a user port numbers in this range and then we have what are called dynamic or 45 00:04:16,950 --> 00:04:21,060 private port numbers also called ephemeral port numbers. 46 00:04:21,060 --> 00:04:23,400 Again people use different terms. 47 00:04:23,400 --> 00:04:24,280 Is it a router. 48 00:04:24,330 --> 00:04:25,560 Is it a router. 49 00:04:25,560 --> 00:04:27,830 Is it a highway or a motorway. 50 00:04:27,870 --> 00:04:29,200 Is it a sneaker. 51 00:04:29,220 --> 00:04:31,290 Is it a trainer or in South Africa. 52 00:04:31,290 --> 00:04:34,980 Is it a tacky tacky as a word that comes from Afrikaans. 53 00:04:35,160 --> 00:04:37,800 But we use that as the English word in South Africa. 54 00:04:37,800 --> 00:04:39,630 So is it a tacky. 55 00:04:39,630 --> 00:04:41,550 Is it a trainer. 56 00:04:41,580 --> 00:04:42,880 Like in the UK. 57 00:04:42,970 --> 00:04:45,500 Was it a sneaker in the USA. 58 00:04:45,540 --> 00:04:51,990 Different terms used by different people but dynamic or random port numbers or private port numbers 59 00:04:52,230 --> 00:04:56,460 or ephemeral port numbers are dynamically or randomly used. 60 00:04:56,460 --> 00:05:04,920 Now you'll notice packet traces actually using a port number in this range 1025 is the source port number 61 00:05:06,000 --> 00:05:12,200 things change over time if I do a search in Google for a femoral port numbers 62 00:05:15,060 --> 00:05:16,590 on Wikipedia. 63 00:05:16,860 --> 00:05:24,030 You can read more detail about how the eye honor recommends those port numbers for dynamic or private 64 00:05:24,030 --> 00:05:24,740 ports. 65 00:05:24,870 --> 00:05:32,380 But many Linux kernels use this range BSD used this range. 66 00:05:32,460 --> 00:05:36,810 Windows XP used this range by default. 67 00:05:36,810 --> 00:05:41,120 So 1025 not 1024 Vista. 68 00:05:41,160 --> 00:05:43,150 Windows 7 2008. 69 00:05:43,170 --> 00:05:51,330 You use the AI on a range Windows 2003 used this range basically different operating systems used different 70 00:05:51,390 --> 00:05:58,950 ranges and then we told all versions of Windows since Windows 2000 to allow you to specify a custom 71 00:05:58,950 --> 00:06:05,370 range in that range 1025 to sixty five thousand five hundred and thirty five. 72 00:06:05,400 --> 00:06:11,220 You can also see that Windows allows you to customize this so you can specify a custom range. 73 00:06:11,220 --> 00:06:17,220 The moral of the story is servers and for the CCMA you need to worry about some of the well-known port 74 00:06:17,220 --> 00:06:25,150 numbers 80 HDP 21 f DP 69 TFT P and there's a few others. 75 00:06:25,270 --> 00:06:26,440 23 is telnet. 76 00:06:26,440 --> 00:06:28,510 22 is SS H. 77 00:06:28,590 --> 00:06:38,320 No the well-known protocols HDP s as an example is 443 you'll get to know the protocols as you work 78 00:06:38,440 --> 00:06:39,390 with networks. 79 00:06:39,490 --> 00:06:44,650 But for the exam study the well-known port numbers and well-known protocols. 80 00:06:44,710 --> 00:06:50,990 So here we can see the pieces using this source port number going to the server. 81 00:06:51,010 --> 00:06:56,980 However what you'll notice and let's show that in the PD you is that the port numbers get swapped round 82 00:06:57,700 --> 00:07:00,070 when the server replies. 83 00:07:00,220 --> 00:07:01,670 So this is the inbound PD. 84 00:07:01,690 --> 00:07:05,950 This is the PD you from the P.C. to the server. 85 00:07:05,950 --> 00:07:12,420 Source mac addresses the P.C. source IP addresses the P.C. source port number is 1025. 86 00:07:12,790 --> 00:07:18,730 But for the reply that gets reversed round source MAC address is the server. 87 00:07:18,730 --> 00:07:25,810 Destination is the P.C. source IP addresses the server destination is the P.C. source port number is 88 00:07:25,890 --> 00:07:26,450 80. 89 00:07:26,470 --> 00:07:29,150 Destination Port number is 1025. 90 00:07:29,470 --> 00:07:35,200 So basically for our communication MAC addresses get swapped round IP addresses get swapped round and 91 00:07:35,200 --> 00:07:36,780 port numbers get swapped round. 92 00:07:36,790 --> 00:07:43,300 So if you talk from your P.C. to my server and port 80 I'll reply from port 80 to the port number that 93 00:07:43,300 --> 00:07:44,800 you've chosen. 94 00:07:44,800 --> 00:07:50,230 The reason why the PRC will choose dynamic port numbers is if you open up two sessions to my server 95 00:07:50,500 --> 00:07:56,510 your first session may use port number 1025 and your second session may use port number one thousand 96 00:07:56,510 --> 00:07:57,470 twenty six. 97 00:07:57,490 --> 00:08:01,830 They should be randomize but often they're not and that's why hackers can often guess what port number 98 00:08:01,830 --> 00:08:06,000 is going to be used next by application but there you go. 99 00:08:06,030 --> 00:08:13,540 That's an example of layer to layer 3 layer for and layer 7. 100 00:08:13,620 --> 00:08:21,570 If we look in the OSA model here they don't show Layer 7 as the protocol here but that's actually the 101 00:08:21,570 --> 00:08:25,900 protocol used in the TPP IP protocol stack. 102 00:08:26,190 --> 00:08:31,050 Again TTP IP model originally 4 layers we now have 5 layers. 103 00:08:31,140 --> 00:08:35,730 So we group layer 5 6 and 7 together as the application. 104 00:08:35,730 --> 00:08:41,270 But we talk about Layer 7 because of the history with the OSA model. 105 00:08:41,340 --> 00:08:43,820 Okay so that was quite detailed. 106 00:08:43,830 --> 00:08:49,230 I'm hoping that helps you understand a bit about port numbers protocol numbers Ethernet types and so 107 00:08:49,230 --> 00:08:49,880 forth. 108 00:08:50,040 --> 00:08:52,500 In the next video I'm going to show you another protocol. 109 00:08:52,710 --> 00:08:59,910 Let's use email and let's say FCP spend some time however going through this yourself having a look 110 00:08:59,910 --> 00:09:01,020 at the different protocols.