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These are the user uploaded subtitles that are being translated: 1 00:00:00,640 --> 00:00:03,020 So what is the USA model and how does it work. 2 00:00:05,070 --> 00:00:12,380 Of course you recall when we talked about the USA model so why don't we take a closer look. 3 00:00:13,140 --> 00:00:22,430 Get into some of these details as you may recall the U.S. model consists of seven layers and the U.S. 4 00:00:22,430 --> 00:00:33,600 I model raw data starting from the very top layer is transferred to a layer below by adding some additional 5 00:00:33,600 --> 00:00:38,090 information about that layer in Each subsequent layer. 6 00:00:38,100 --> 00:00:44,660 Then when the data is transmitted to the other party the data is transmitted from bottom to top 7 00:00:47,770 --> 00:00:59,250 So data is transmitted according to this always a model as follows Layer 7 application the application 8 00:00:59,250 --> 00:01:03,540 layer is where users actually communicate with a computer. 9 00:01:03,540 --> 00:01:11,370 OK so it doesn't have a top layer so that means it's not possible to provide service to that layer. 10 00:01:11,580 --> 00:01:19,030 The way we do another layer even if you remove all network components network guards etc from your system 11 00:01:19,030 --> 00:01:25,120 you can still use a browser such as Google Chrome Firefox to browse local HDL documents. 12 00:01:25,120 --> 00:01:33,340 Yeah however if you do want to access a Web page via HDP your browser will contact the application layer 13 00:01:34,060 --> 00:01:35,600 and then respond to your request. 14 00:01:39,290 --> 00:01:47,210 Well your 6 presentation so layer in which the data to be sent is converted into a common format that 15 00:01:47,220 --> 00:01:53,490 can be understood by the computer receiving the data resides on layer 6. 16 00:01:53,740 --> 00:02:02,790 This way is actually a converter if you will and it provides encoding and translation functions it performs 17 00:02:02,790 --> 00:02:10,700 tasks such as data compression and encryption and it ensures that the data that's transmitted from the 18 00:02:10,700 --> 00:02:20,130 application lever system can be read by the application layer of the other party layer five session 19 00:02:22,540 --> 00:02:29,430 on setting it up using and ending the session between two computers is done in this layer. 20 00:02:29,630 --> 00:02:36,440 So when a computer is in communication with multiple computers at the same time it will allow the user 21 00:02:36,440 --> 00:02:39,200 to speak to the current computers when necessary. 22 00:02:41,480 --> 00:02:50,970 Therefore transport this layer segments and then reassemble as data into a data stream the services 23 00:02:50,970 --> 00:02:58,890 in this layer divide reassemble and then combine data from top tier applications into the same data 24 00:02:58,890 --> 00:03:05,340 stream so in this way in case of data loss it will be a lot easier to respond because the data will 25 00:03:05,340 --> 00:03:08,430 be smaller. 26 00:03:08,440 --> 00:03:14,890 It also assigns a sequence number to each part in order to ensure that any missing parts will be identified 27 00:03:15,250 --> 00:03:24,040 and then completed by the recipient and TTP as well as UDP protocols will work in this layer. 28 00:03:27,430 --> 00:03:35,800 Layer 3 network so Layer 3 manages device addressing monitors the location of devices on the network 29 00:03:36,610 --> 00:03:42,610 determines the best way to move data it's responsible for transmitting traffic between devices that 30 00:03:42,610 --> 00:03:46,160 are not connected locally. 31 00:03:46,190 --> 00:03:54,010 So this is the layer that will select the best way to achieve the targeted data and this process is 32 00:03:54,010 --> 00:04:04,330 called routing and the device that performs this process is called you guessed it router Layer 2 data 33 00:04:04,330 --> 00:04:05,950 link. 34 00:04:05,980 --> 00:04:11,440 So basically this layer will convert messages from the network layer into bits for the physical layer 35 00:04:11,950 --> 00:04:18,090 most of the data link layer occurs within the network car it identifies other computers on the network 36 00:04:19,610 --> 00:04:28,290 it determines who is currently using the cable performs the tasks of checking data from the physical 37 00:04:28,290 --> 00:04:39,150 connection for errors and switches devices according to their MAC addresses so this layer faulty packages 38 00:04:39,150 --> 00:04:48,100 are checked and then sent again layer one physical layer the physical layer or the lowest layer is the 39 00:04:48,100 --> 00:04:55,520 layer closest to the physical network environment it's one that sends and receives bits so it deals 40 00:04:55,520 --> 00:05:02,160 with how to convert ones and zeros to electrical light or radio signals both parties must agree on the 41 00:05:02,160 --> 00:05:10,040 same rules to ensure communication and then when the data is transmitted to the other party this time 42 00:05:10,040 --> 00:05:15,410 the process from the first layer to the seventh layer is performed in reverse order. 5433