1 00:00:00,770 --> 00:00:06,410 All right, so since there's really nothing much to say about the physical layer, I mean, because 2 00:00:06,740 --> 00:00:11,090 in this course, we're really looking at the digital side of networking. 3 00:00:11,120 --> 00:00:16,130 I'd like to just skip that and start with the second one, the datalink layer. 4 00:00:17,240 --> 00:00:25,640 The datalink layer is the second layer and the U.S. Open Systems Interconnection seven layer reference 5 00:00:25,640 --> 00:00:26,050 model. 6 00:00:26,570 --> 00:00:34,640 Now it responds to service requests from the network layer above it and issues service requests to the 7 00:00:34,640 --> 00:00:36,170 physical layer below it. 8 00:00:36,800 --> 00:00:37,130 Right. 9 00:00:37,880 --> 00:00:45,440 So the datalink layer is responsible for encoding bits into packets prior to transmission and then decoding 10 00:00:45,440 --> 00:00:47,960 the packets back in the bits at the destination. 11 00:00:48,970 --> 00:00:54,310 And bit, by the way, are the most basic unit of information in computing and communications. 12 00:00:55,200 --> 00:01:03,540 Packets are the fundamental unit of information transport in all modern computer networks and increasingly 13 00:01:03,540 --> 00:01:05,850 in other communications networks as well. 14 00:01:07,660 --> 00:01:10,690 So the datalink layer is also responsible for. 15 00:01:12,110 --> 00:01:22,610 Logical link, control media access control hardware, addressing error detection and handling and defining 16 00:01:22,610 --> 00:01:24,350 physical labor standards. 17 00:01:25,650 --> 00:01:32,100 It provides reliable data transfer by transmitting packets with the necessary synchronization error 18 00:01:32,100 --> 00:01:33,930 control and flow control. 19 00:01:34,950 --> 00:01:38,310 The data link layer is divided into two sub layers. 20 00:01:39,300 --> 00:01:46,950 First, the media access control, MAK subletter, the governor's protocol, access to the physical 21 00:01:46,950 --> 00:01:54,390 network medium through the Mac addresses that are typically assigned to all ports on a router, multiple 22 00:01:54,390 --> 00:02:00,090 devices on the same physical link can uniquely identify one another at the data link layer. 23 00:02:01,000 --> 00:02:06,550 Mac addresses are used in addition to the network addresses that are typically configured manually on 24 00:02:06,550 --> 00:02:07,930 ports within a network. 25 00:02:09,880 --> 00:02:17,350 Now, secondly, the logical link control, or LLC subletter, manages communications between devices 26 00:02:17,350 --> 00:02:19,450 over a single link of a network. 27 00:02:20,140 --> 00:02:28,240 This subletter supports fields in link layer frames that enable multiple higher layer protocols to share 28 00:02:28,420 --> 00:02:29,980 a single physical link. 29 00:02:31,590 --> 00:02:38,610 So here we have some protocols and the datalink layer and some physical media and connection methodologies 30 00:02:38,610 --> 00:02:39,780 in the physical layer. 31 00:02:41,220 --> 00:02:47,610 Ethernet and Aido to dot one one wireless lan are the best known protocols of the datalink layer. 32 00:02:49,840 --> 00:02:55,840 Ethernet is the name of the most commonly used network protocol that controls how data is transmitted 33 00:02:55,870 --> 00:02:58,840 over land, which is a local area network. 34 00:02:59,920 --> 00:03:06,430 Now you need to have a network interface card in the device that you want to connect to the network. 35 00:03:07,730 --> 00:03:12,110 I know it probably seems pretty obvious to you, but I just wanted to make sure that we're all on the 36 00:03:12,110 --> 00:03:12,680 same page. 37 00:03:14,020 --> 00:03:21,850 A wireless local area network, or LAN, is a wireless computer network protocol that links two or more 38 00:03:21,850 --> 00:03:28,930 devices using wireless communication within a limited area such as a home or school computer lab or 39 00:03:28,930 --> 00:03:29,740 office building. 40 00:03:31,330 --> 00:03:37,580 And this gives users the ability to move around within a local coverage area and still be connected 41 00:03:37,580 --> 00:03:38,390 to the network. 42 00:03:39,610 --> 00:03:48,310 Most modern lands are based on the eye Tripoli Aido to one one standard and are marketed under the Wi-Fi 43 00:03:48,310 --> 00:03:48,880 brand name.