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These are the user uploaded subtitles that are being translated: 1 00:00:00,000 --> 00:00:07,000 align:middle line:84% So what is the difference between a routed protocol and a routing protocol? 2 00:00:07,000 --> 00:00:16,000 align:middle line:84% Now a routed protocol carries user data, example, would be IPv4 or IPv6. 3 00:00:16,000 --> 00:00:21,000 align:middle line:84% When you use a higher layer protocols such asHTTP or FTP 4 00:00:21,000 --> 00:00:26,000 align:middle line:84% that protocol is using a lower layer protocols 5 00:00:26,000 --> 00:00:33,000 align:middle line:84% such as IPv4 or IPv6 to carry the user data from one device to another. 6 00:00:33,000 --> 00:00:35,000 align:middle line:84% So when you connect to a website 7 00:00:35,000 --> 00:00:42,000 align:middle line:84% and you're viewing a webpage that would be deemed to be routed data. 8 00:00:42,000 --> 00:00:48,000 align:middle line:84% Data from the web server is being routed to your PC 9 00:00:48,000 --> 00:00:56,000 align:middle line:84% now the addressing scheme used by routed protocol is based on this specific protocol 10 00:00:56,000 --> 00:01:04,000 align:middle line:84% such a IPv4 using a 32 bit address and IPv6 using 128 bit address. 11 00:01:04,000 --> 00:01:10,000 align:middle line:84% Now how do routers know where devices are in a network? 12 00:01:10,000 --> 00:01:14,000 align:middle line:84% As an example, my PC is based in the UK 13 00:01:14,000 --> 00:01:20,000 align:middle line:84% but when I go to Facebook.com traffic is sent from my PC 14 00:01:20,000 --> 00:01:24,000 align:middle line:84% to Facebook based in California and back again, 15 00:01:24,000 --> 00:01:30,000 align:middle line:84% How does my device actually reach the facebook service 16 00:01:30,000 --> 00:01:37,000 align:middle line:84% in a data center in California and how does the data get back to my PC in the UK? 17 00:01:37,000 --> 00:01:42,000 align:middle line:84% How is the user data forwarded from one device to another? 18 00:01:42,000 --> 00:01:45,000 align:middle line:84% Now it’s important to realize that every router 19 00:01:45,000 --> 00:01:51,000 align:middle line:84% along the path between my PC in the UK and facebook.com 20 00:01:51,000 --> 00:01:54,000 align:middle line:84% makes an independent routing decision. 21 00:01:54,000 --> 00:01:59,000 align:middle line:84% As an example, if I trace to facebook.com 22 00:01:59,000 --> 00:02:01,000 align:middle line:84% and in this case, I’m going to set the timeout 23 00:02:01,000 --> 00:02:05,000 align:middle line:84% to a low value such as 50 milliseconds. 24 00:02:05,000 --> 00:02:11,000 align:middle line:84% Traffic is being forwarded from my PC 25 00:02:11,000 --> 00:02:17,000 align:middle line:84% on hop-by-hop bases from 1 router to the next 26 00:02:17,000 --> 00:02:20,000 align:middle line:84% until it hopefully reaches facebook.com 27 00:02:20,000 --> 00:02:24,000 align:middle line:84% every one of these hops is an independent router 28 00:02:24,000 --> 00:02:27,000 align:middle line:84% making independent routing decisions. 29 00:02:27,000 --> 00:02:31,000 align:middle line:84% Now Facebook and a lot of other big websites 30 00:02:31,000 --> 00:02:34,000 align:middle line:84% will have data centers scattered around the world 31 00:02:34,000 --> 00:02:38,000 align:middle line:84% so my traffic may not actually be going all the way to the US 32 00:02:38,000 --> 00:02:41,000 align:middle line:84% but maybe going to a local data center in Europe 33 00:02:41,000 --> 00:02:45,000 align:middle line:84% that all depends on how the network is configured. 34 00:02:45,000 --> 00:02:48,000 align:middle line:84% These routing decisions made by routers 35 00:02:48,000 --> 00:02:52,000 align:middle line:84% is known as the hop-by-hop routing paradigm 36 00:02:52,000 --> 00:02:57,000 align:middle line:84% with unicast traffic routing is based on destination address only 37 00:02:57,000 --> 00:02:59,000 align:middle line:84% not on source address 38 00:02:59,000 --> 00:03:03,000 align:middle line:84% so routers decide where traffic goes based on the destination IP address 39 00:03:03,000 --> 00:03:08,000 align:middle line:84% in my example it's this address and routers will decide 40 00:03:08,000 --> 00:03:13,000 align:middle line:84% where to route traffic based on the destination IP address 41 00:03:13,000 --> 00:03:15,000 align:middle line:84% and information stored in routing tables. 42 00:03:15,000 --> 00:03:20,000 align:middle line:84% Every router along the path needs to determine 43 00:03:20,000 --> 00:03:25,000 align:middle line:84% an outgoing interface to forward traffic to reach the destination IP address. 44 00:03:25,000 --> 00:03:32,000 align:middle line:84% To do that routers communicate information about networks using routing protocols. 45 00:03:32,000 --> 00:03:38,000 align:middle line:84% They will then determine the best path to the destination IP address 46 00:03:38,000 --> 00:03:43,000 align:middle line:84% using criteria specific to that individual routing protocol. 47 00:03:43,000 --> 00:03:48,000 align:middle line:84% As an example, RIP uses hop count to determine the best path. 48 00:03:48,000 --> 00:03:53,000 align:middle line:84% OSPF uses the bandwidth of interfaces to determine the best path. 49 00:03:53,000 --> 00:03:59,000 align:middle line:84% EIGRP uses bandwidth and delays to determine the best path. 50 00:03:59,000 --> 00:04:04,000 align:middle line:84% So routing protocols are used to automatically advertise networks 51 00:04:04,000 --> 00:04:07,000 align:middle line:84% between routers and that’s how routers learn 52 00:04:07,000 --> 00:04:11,000 align:middle line:84% about the available networks in a topology. 53 00:04:11,000 --> 00:04:13,000 align:middle line:84% It’s also important to note 54 00:04:13,000 --> 00:04:17,000 align:middle line:84% that if a router doesn’t know about the destination IP address. 55 00:04:17,000 --> 00:04:22,000 align:middle line:84% In other words, information about that destination IP address 56 00:04:22,000 --> 00:04:27,000 align:middle line:84% is not in its routing table it will drop unicast packets. 57 00:04:27,000 --> 00:04:30,000 align:middle line:84% Destination IP address is a match against networks 58 00:04:30,000 --> 00:04:33,000 align:middle line:84% and subnets in the routers routing table 59 00:04:33,000 --> 00:04:38,000 align:middle line:84% so if a router receives traffic going to an IP address of let say 10.1.1.1 60 00:04:38,000 --> 00:04:44,000 align:middle line:84% but that IP address doesn’t match a network in the routers routing table. 61 00:04:44,000 --> 00:04:49,000 align:middle line:84% The router will drop the packets because it doesn’t know where to forward them 62 00:04:49,000 --> 00:04:56,000 align:middle line:84% Essentially if you tell a router send traffic to IP address 10.1.1.1 63 00:04:56,000 --> 00:05:02,000 align:middle line:84% and the router doesn’t know how to get to that network or IP address. 64 00:05:02,000 --> 00:05:05,000 align:middle line:84% The router will drop that traffic 65 00:05:05,000 --> 00:05:09,000 align:middle line:84% if there is no matching route in the routing table traffic gets dropped. 66 00:05:09,000 --> 00:05:13,000 align:middle line:84% This applies specifically to unicast packets 67 00:05:13,000 --> 00:05:17,000 align:middle line:84% where we are doing routers based on destination IP address. 68 00:05:17,000 --> 00:05:23,000 align:middle line:84% So in summary, routing protocols allow routers to learn about destination networks. 69 00:05:23,000 --> 00:05:29,000 align:middle line:84% That facilitates the change of routed information between devices. 70 00:05:29,000 --> 00:05:34,000 align:middle line:84% Routers can dynamically learn about networks in the topology 71 00:05:34,000 --> 00:05:39,000 align:middle line:84% and can then make routing decisions based on different criteria 72 00:05:39,000 --> 00:05:45,000 align:middle line:84% such as bandwidth hop count or delay to determine the best path. 73 00:05:45,000 --> 00:05:50,000 align:middle line:84% Routers then simply choose an outgoing interface based on the routing table 74 00:05:50,000 --> 00:05:55,000 align:middle line:84% and will then forward packets out of that interface to reach a destination. 8969