1 00:00:00,770 --> 00:00:06,380 ‫All right, so since there's really nothing much to say about the physical layer, I mean, because 2 00:00:07,520 --> 00:00:11,060 ‫in this course we're really looking at the digital side of networking. 3 00:00:11,090 --> 00:00:13,880 ‫I'd like to just skip that and start with the second one. 4 00:00:14,300 --> 00:00:16,130 ‫The data link layer. 5 00:00:17,240 --> 00:00:25,610 ‫The datalink layer is a second layer and the Osai Open Systems Interconnection seven layer reference 6 00:00:25,610 --> 00:00:26,040 ‫model. 7 00:00:26,600 --> 00:00:34,610 ‫Now it responds to service requests from the network layer above it and issues service requests to the 8 00:00:34,610 --> 00:00:37,130 ‫physical layer below it, right? 9 00:00:37,910 --> 00:00:44,870 ‫So the data link layer is responsible for encoding bits into packets prior to transmission and then 10 00:00:44,870 --> 00:00:47,960 ‫decoding the packets back in the bits at the destination. 11 00:00:49,000 --> 00:00:54,280 ‫And --, 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 --> 00:01:05,820 ‫in other communications networks as well. 14 00:01:07,690 --> 00:01:10,720 ‫So the data link layer is also responsible for. 15 00:01:12,080 --> 00:01:21,770 ‫Logical link, control, media access control, hardware, addressing error detection and handling and 16 00:01:21,770 --> 00:01:24,320 ‫defining physical layer standards. 17 00:01:25,650 --> 00:01:32,640 ‫It provides reliable data transfer by transmitting packet with a necessary synchronization, error control 18 00:01:32,850 --> 00:01:33,930 ‫and flow control. 19 00:01:34,950 --> 00:01:38,250 ‫The data link layer is divided into two sub layers. 20 00:01:39,300 --> 00:01:48,180 ‫First, the media access control Mac Sub Layer governs protocol access to the physical network medium 21 00:01:49,020 --> 00:01:52,980 ‫through the Mac addresses that are typically assigned to all ports on a router. 22 00:01:53,820 --> 00:02:00,060 ‫Multiple devices on the same physical link can uniquely identify one another at the data link layer. 23 00:02:01,000 --> 00:02:06,520 ‫Mac addresses are used in addition to the network addresses that are typically configured manually on 24 00:02:06,520 --> 00:02:07,920 ‫ports within a network. 25 00:02:09,880 --> 00:02:17,350 ‫Now, secondly, the Logical Link Control, or LLC sub layer, manages communications between devices 26 00:02:17,350 --> 00:02:19,420 ‫over a single link of a network. 27 00:02:20,140 --> 00:02:28,240 ‫This sub layer supports fields in link layer frames that enable multiple higher layer protocols to share 28 00:02:28,450 --> 00:02:29,950 ‫a single physical link. 29 00:02:31,590 --> 00:02:38,580 ‫So here we have some protocols and the data link layer and some physical media and connection methodologies 30 00:02:38,580 --> 00:02:39,750 ‫in the physical layer. 31 00:02:41,250 --> 00:02:47,610 ‫Ethernet and 8.2.1 one wireless LAN are the best known protocols of the data link layer. 32 00:02:49,840 --> 00:02:55,810 ‫Ethernet is the name of the most commonly used network protocol that controls how data is transmitted 33 00:02:55,810 --> 00:02:58,840 ‫over land, which is a local area network. 34 00:02:59,950 --> 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 00:03:07,760 --> 00:03:12,080 ‫I know it probably seems pretty obvious to you, but I just wanted to make sure that we're all on the 36 00:03:12,080 --> 00:03:12,680 ‫same page. 37 00:03:14,020 --> 00:03:21,640 ‫A wireless local area network, or W LAN, is a wireless computer network protocol that links two or 38 00:03:21,640 --> 00:03:28,570 ‫more devices using wireless communication within a limited area such as a home or school computer lab 39 00:03:28,570 --> 00:03:29,710 ‫or office building. 40 00:03:31,370 --> 00:03:37,550 ‫And this gives users the ability to move around within a local coverage area and still be connected 41 00:03:37,550 --> 00:03:38,360 ‫to the network. 42 00:03:39,610 --> 00:03:48,640 ‫Most modern lands are based on the eye Tripoli 8.2.1 one standard and are marketed under the Wi-Fi brand 43 00:03:48,640 --> 00:03:48,880 ‫name.