WEBVTT 00:00.660 --> 00:10.200 The PDU, The protocol data unit in each layer contains the payload data that is being transmitted, 00:10.200 --> 00:17.040 and it's a common to prefix a header which contains information required for the payload data to be 00:17.040 --> 00:23.250 transmitted, such as the addresses of the source and destination nodes on the network to the payload 00:23.250 --> 00:23.710 data. 00:23.730 --> 00:33.480 So sometimes the protocol data unit PDU also has a footer here that is suffixed to the payload data 00:33.480 --> 00:39.900 and contains values needed to ensure correct transmission, such as error checking information. 00:39.900 --> 00:48.960 And here in this diagram I created how pdus are laid out in the eips. 00:48.990 --> 00:55.260 Remember from the previous lectures IPS means Internet protocol suite. 00:58.880 --> 01:01.880 So let's get started with the application layer here. 01:01.880 --> 01:09.380 So you can see here we have layer four, we have application session, um, internet layer and the link 01:09.380 --> 01:09.920 layer. 01:09.950 --> 01:15.830 Now I will explain all of these layers and their payloads heaters one by one. 01:15.830 --> 01:23.720 So the TCP header contains a source and destination port number which is here. 01:25.280 --> 01:28.910 Source and destination port number here. 01:29.630 --> 01:36.860 And these port numbers allow a single node to have a multiple unique network. 01:36.860 --> 01:49.580 Connections and port numbers for TCP and UDP ranges from 0 to 65,500. 01:51.060 --> 01:51.870 35. 01:57.010 --> 02:01.780 And the most port numbers are assigned as needed to new connections. 02:01.780 --> 02:08.350 But some numbers have been given a special assignment such as the Port 80 for HTTP. 02:08.380 --> 02:14.650 You can find the current list of assigned port numbers in the ATC services file on the most Unix like 02:14.650 --> 02:23.380 operating system, but you can also check in from the Wikipedia from internet and TCP payload and header 02:23.380 --> 02:32.290 are commonly called the segment where the UDP payload and header are commonly called a datagram. 02:33.370 --> 02:38.260 The IPA protocol uses a source and destination headers. 02:41.420 --> 02:51.290 The destination address lost the data to be sent to a specific node on the network and the source address. 02:51.320 --> 03:01.100 Lost the receiver of the data to know which node sent the data and lost the receiver to reply to the 03:01.100 --> 03:01.820 sender. 03:07.240 --> 03:15.910 IPv4 uses 32 bit addresses, which you will typically see written as a four numbers separated by dots 03:15.910 --> 03:17.500 such as this. 03:18.580 --> 03:20.950 192168. 03:25.040 --> 03:27.230 192168. 03:27.260 --> 03:28.040 Here. 03:29.420 --> 03:30.620 Ten and one. 03:30.620 --> 03:32.300 So this is an example. 03:32.330 --> 03:43.010 IP version four, IP address and IPv6 actually let me notify their IP version four. 03:44.430 --> 03:44.700 So. 03:45.090 --> 03:48.120 But the IPV six here. 03:50.180 --> 03:56.690 IPv6 uses 128 bit addresses. 03:58.850 --> 04:07.100 Because 32 bit addresses aren't sufficient for the numbers of nodes on the modern networks. 04:07.930 --> 04:14.810 IPv6 addresses are usually written as a hexadecimal number separated by colons such as. 04:14.830 --> 04:25.330 For example, if a 80 0004 times zero here, actually let me increase the size it here. 04:26.250 --> 04:27.240 000. 04:27.510 --> 04:28.740 And. 04:30.280 --> 04:32.620 So this is an example. 04:32.650 --> 04:35.800 IPV four IPV six address. 04:36.690 --> 04:39.510 Long strings of four times zero. 04:39.510 --> 04:41.910 As you can see here, we've written like that. 04:42.270 --> 04:48.960 Long strings of 000 numbers are collapsed into two columns. 04:48.960 --> 04:57.060 For example, if you want to read, write this IPV IP version six number easily. 04:57.060 --> 04:58.530 You can also write like that. 04:58.530 --> 04:59.190 For example. 04:59.190 --> 05:00.690 One, two, three. 05:00.780 --> 05:02.370 So one. 05:05.190 --> 05:05.820 Two, three. 05:13.860 --> 05:18.050 The Internet also contains source and destination address. 05:19.430 --> 05:22.090 Source and destination address. 05:22.950 --> 05:32.310 Ethernet uses a 64 bit value called a media access control address, which is typically set during a 05:32.310 --> 05:35.400 manufacture of the Ethernet adapter. 05:35.400 --> 05:44.370 And you will usually see MAC addresses written as a series of hexadecimal numbers separated by dashes 05:44.370 --> 05:45.810 or colons. 05:46.170 --> 05:49.980 For example, Mac Address three writes like this. 05:50.100 --> 05:51.270 Example zero. 05:51.870 --> 05:52.440 A. 05:53.440 --> 05:54.220 With dashes. 05:54.220 --> 05:55.430 We will separate here. 05:55.600 --> 05:58.330 28 and nine. 05:59.590 --> 06:02.080 For a five. 06:03.040 --> 06:12.370 So this is an example media access control address and the Ethernet payload, including the header and 06:12.370 --> 06:17.230 footer is commonly referred as frame.