WEBVTT 00:05.290 --> 00:07.000 So welcome back, guys. 00:07.000 --> 00:12.310 In this section of the course, we will going to discuss and understand the concept of Tlvs. 00:12.310 --> 00:15.550 So Tlv stands for type, length and value. 00:15.700 --> 00:21.400 Tlv is a mechanism of packaging the data in a type length value order. 00:21.430 --> 00:22.150 Right. 00:22.150 --> 00:29.230 And the benefits of the Tlv is that that it's a very flexible mechanism to package the data and send 00:29.230 --> 00:30.790 it out to the recipient. 00:30.820 --> 00:33.790 It is easy to add or remove the data. 00:33.880 --> 00:41.890 The concept of TLB requires that there is no need to define any additional key structures in your program. 00:41.890 --> 00:42.790 Right. 00:42.790 --> 00:49.600 And the recipient machine can ignore the data which recipient machine do not understand, and the recipient 00:49.600 --> 00:54.460 machine can selectively process the data which it recognizes. 00:55.020 --> 01:02.100 So you will understand these benefits better once we will be finished up with the concept and do the 01:02.100 --> 01:03.120 assignment. 01:03.570 --> 01:09.420 Those who are already familiar with the concept can straightaway jump to the assignment section. 01:10.650 --> 01:12.300 And those who are listening. 01:12.300 --> 01:14.250 The term TV for the first time. 01:14.250 --> 01:15.870 Please stay with me. 01:15.900 --> 01:20.460 So now let us try to understand the Tlv with the help of an example straight away. 01:20.580 --> 01:26.460 So you can see that the diagram of the right hand side shows three TVs packed together. 01:26.760 --> 01:33.420 This is the first tlv followed by the second tlv and followed by the third tlv. 01:33.690 --> 01:39.570 You can see that in each Tlv there are three parts type length and value. 01:40.020 --> 01:43.200 The type field of the Tlv is one byte. 01:43.230 --> 01:50.490 The length field of the Tlv is one byte, whereas the value field of the Tlv is of variable size. 01:52.910 --> 01:58.040 Each TLB is identified using a unique code called type. 01:58.730 --> 02:04.040 And since we are giving only one byte of space to represent the type value. 02:04.070 --> 02:08.690 Therefore, type field goes from value 0 to 255. 02:08.690 --> 02:09.350 Right. 02:09.380 --> 02:14.870 Similarly, we have taken only one byte of space in order to represent the length. 02:14.900 --> 02:21.530 This length value represents the length of the data which is present in the value part of the TLB. 02:23.210 --> 02:30.260 So in this example, the name Abhishek Sagar is actually 32 bytes long because the length field of the 02:30.260 --> 02:32.180 Tlv is set to 32. 02:32.210 --> 02:32.950 Right. 02:32.960 --> 02:40.820 Similarly, in the second Tlv, the length of the value field is 64 bytes and the length of the value 02:40.820 --> 02:44.020 field in the third Tlv is only eight bytes. 02:44.030 --> 02:44.750 Right. 02:45.740 --> 02:55.700 Now, technically we have defined three types of tlvs here the Tlv type one, type two and type three. 02:55.730 --> 02:56.390 Right. 02:56.390 --> 03:03.590 So you can define these constants in your program and assign a unique integer number to these constants. 03:04.430 --> 03:06.410 Now let us try to understand that. 03:06.410 --> 03:08.210 What is the information? 03:08.240 --> 03:10.030 A given type. 03:10.070 --> 03:11.210 Tell us. 03:11.600 --> 03:15.830 So let us suppose that I define a tlv of type one. 03:16.010 --> 03:19.520 So in this case the Tlv of type one. 03:19.520 --> 03:21.270 Tell me two type of information. 03:21.290 --> 03:27.260 The first information is that that the type of information which is present in the value part of the 03:27.260 --> 03:33.740 tlv is of type string and the length of one unit of data is 32 bytes. 03:34.340 --> 03:41.930 Similarly, the second type of tlv I have defined as website tlv code whose value I have taken it as 03:41.930 --> 03:42.650 two. 03:42.650 --> 03:48.260 And when I say that I have a tlv of type two, it conveys me two types of information. 03:48.470 --> 03:54.770 The first information is that that the data which is present in the value part of the Tlv is of type 03:54.770 --> 03:55.460 string. 03:55.760 --> 04:01.910 And the second information is that that the unit length of this data is 64 bytes. 04:02.710 --> 04:07.210 Similarly, the Tlv of type three tell me two types of information. 04:07.300 --> 04:12.640 The first information is that that the type of the data which is present in the value part of the Tlv 04:12.670 --> 04:20.470 is of type integer and the size of unit data of this tlv is only eight bytes. 04:21.230 --> 04:27.530 So tlv code points that is these values one, two and three gives me two information. 04:27.530 --> 04:29.600 What is the data type of the value? 04:29.600 --> 04:30.500 Is it a string? 04:30.500 --> 04:31.520 Is it integer? 04:31.520 --> 04:32.330 Is it float? 04:32.330 --> 04:35.450 Is it IP address or is it something else? 04:35.480 --> 04:42.830 And the second information that the Tlv type gives me is that that what is the length of one unit of 04:42.830 --> 04:45.680 data present in the value part of the Tlv? 04:45.920 --> 04:54.680 And also note that that the one byte of Tlv type and one byte of tlv length together they are called 04:54.710 --> 04:56.000 tlv overhead. 04:56.000 --> 04:56.600 Right? 04:56.600 --> 05:00.770 And the size of the tlv overhead is two bytes which is constant. 05:00.770 --> 05:01.520 Right. 05:01.760 --> 05:07.720 The type and the length portion of the Tlv is often termed as tlv overhead. 05:07.730 --> 05:13.460 So in the next lecture video we will going to understand more about Tlv using second example.