1 00:00:00,300 --> 00:00:07,680 What I'd like to point out once again is that each website is resolved to a different IP address. 2 00:00:08,039 --> 00:00:15,810 Lastly, if I ping CNN.com, notice that that also resolves to an IP address, but it's different to 3 00:00:15,810 --> 00:00:17,370 the previous examples. 4 00:00:17,670 --> 00:00:23,790 DNS is doing the name resolution, so it's resolving a domain name to an IP address. 5 00:00:23,790 --> 00:00:28,650 And that's how I'm learning the IP address of CNN.com or Google.com. 6 00:00:28,770 --> 00:00:34,800 You can ping many of the well known websites on the Internet to find out what the IP addresses are. 7 00:00:34,830 --> 00:00:42,150 You could also use GNSS lookup, which just does a DNS resolution of a domain name rather than trying 8 00:00:42,150 --> 00:00:43,710 to ping the server. 9 00:00:44,010 --> 00:00:50,250 So in summary, the devices on the Internet have been configured with IP version for addresses. 10 00:00:50,310 --> 00:00:55,140 I'll explain more about the formatting of IP addresses in the next few minutes. 11 00:00:55,140 --> 00:01:02,520 But for now, just take note that every device has an IP address and that includes my own machine. 12 00:01:02,790 --> 00:01:09,170 The command IP config will show me the IP address on my local machine when using windows. 13 00:01:09,180 --> 00:01:14,340 So in this example, my IP version for address is ten .0.0.6. 14 00:01:14,490 --> 00:01:20,220 You'll also notice here that I have an IP version six address of 2001. 15 00:01:20,220 --> 00:01:21,280 Colon 20. 16 00:01:21,300 --> 00:01:22,950 Colon Colon two. 17 00:01:22,980 --> 00:01:28,530 In this video, we concentrating on IP version four addresses, but in another video, I'll explain 18 00:01:28,530 --> 00:01:30,060 IP version six. 19 00:01:30,240 --> 00:01:36,030 IP version six is becoming more and more important because IP addresses are now exhausted in certain 20 00:01:36,030 --> 00:01:37,200 parts of the world. 21 00:01:37,620 --> 00:01:45,660 IP version four or Internet protocol version four is a layer three or network layer protocol as per 22 00:01:45,660 --> 00:01:47,190 the OCI model. 23 00:01:47,310 --> 00:01:50,270 In a different video I explained the OCI model. 24 00:01:50,280 --> 00:01:53,880 So if you're not sure about layers, please refer to that video. 25 00:01:54,090 --> 00:01:57,280 IP version four is a connection less protocol. 26 00:01:57,300 --> 00:01:59,730 In other words, there are no sessions formed. 27 00:01:59,730 --> 00:02:06,510 When traffic is transmitted, the transmitter simply sends data without notification to the receiver. 28 00:02:06,540 --> 00:02:10,350 No status information is sent back from the receiver to the transmitter. 29 00:02:10,350 --> 00:02:11,700 It's totally connection. 30 00:02:11,700 --> 00:02:18,300 Less TCP IP or transmission control protocol, on the other hand is connection orientated. 31 00:02:18,540 --> 00:02:25,650 TCP will set up a session, so before transmission takes place in TCP IP, the transmitter sends what's 32 00:02:25,650 --> 00:02:29,940 called a sun or synchronization message to the receiver. 33 00:02:29,970 --> 00:02:38,220 There's a sun ack message from the receiver to the transmitter and then a ack or acknowledgement message 34 00:02:38,220 --> 00:02:40,170 from the transmitter to the receiver. 35 00:02:40,170 --> 00:02:48,510 So before any data is transmitted, but devices using TCP go through what's called the three way handshake 36 00:02:48,600 --> 00:02:51,480 syn sent EC and ACH. 37 00:02:51,600 --> 00:02:54,750 IP, on the other hand, doesn't do any of that. 38 00:02:54,780 --> 00:02:58,620 Each packet is treated independently of other packets. 39 00:02:58,620 --> 00:03:03,720 That's why traffic can take different paths to get to a destination. 40 00:03:04,020 --> 00:03:10,140 Routers will route the traffic via different paths based on options such as load balancing. 41 00:03:10,140 --> 00:03:17,070 Because each packet is independent and IP is a connection less protocol routers can also base routing 42 00:03:17,070 --> 00:03:25,260 decisions on different values, such as bandwidth or hop count, but it is possible that packets from 43 00:03:25,260 --> 00:03:31,650 one session take divergent or different paths to get to a destination. 44 00:03:32,010 --> 00:03:39,060 So for example, RIP will base its routing decisions on hop count, which is not good, and hence REP 45 00:03:39,060 --> 00:03:41,370 is not used that often anymore. 46 00:03:41,610 --> 00:03:44,760 OSPF will base it on bandwidth. 47 00:03:44,850 --> 00:03:49,580 Other routing protocols will use their own metrics to determine the best path. 48 00:03:49,590 --> 00:03:56,550 I'll be discussing routing protocols in more detail later in this course, but in brief, routing protocols 49 00:03:56,550 --> 00:04:00,840 determine the best path or best route from A to B. 50 00:04:01,140 --> 00:04:07,950 This is based on the hierarchical addressing structure in IP version four and IP version six, where 51 00:04:07,950 --> 00:04:12,300 we have both a network and host portion as part of the address. 52 00:04:12,720 --> 00:04:18,390 Routers based their routing decisions on the network portion of the address rather than on the host 53 00:04:18,390 --> 00:04:20,250 portion of the address. 54 00:04:20,610 --> 00:04:24,240 And I'll explain network and host portions in a moment. 55 00:04:24,420 --> 00:04:28,680 IP also only gives best effort delivery of packets. 56 00:04:28,680 --> 00:04:31,890 There is no guarantee of packet delivery. 57 00:04:31,890 --> 00:04:39,090 Any packet could be misdirected, it could be duplicated, or it could be lost in transmission when 58 00:04:39,090 --> 00:04:40,890 sent to a destination. 59 00:04:40,890 --> 00:04:44,850 And that should be expected in IP transmissions. 60 00:04:45,180 --> 00:04:51,960 Once again, TCP, which is a connection orientated protocol, has the ability to retransmit packets 61 00:04:51,960 --> 00:04:53,010 that go missing. 62 00:04:53,070 --> 00:04:59,700 UDP Another layer for protocol doesn't retransmit packets if they get dropped. 63 00:04:59,980 --> 00:05:04,040 Simply lost and the applications need to take care of that. 64 00:05:04,060 --> 00:05:07,580 There is also no data recovery features in IP. 65 00:05:07,600 --> 00:05:14,590 If the packet, for example, gets corrupted, the end devices need to handle that and not the routers 66 00:05:14,590 --> 00:05:15,490 in between. 67 00:05:15,820 --> 00:05:22,120 So in summary, IP has no built in sessions, no data recovery, no transmissions. 68 00:05:22,330 --> 00:05:29,980 Higher layer protocols such as TCP IP will need to handle dropped packets, corrupted packets, misdirected 69 00:05:29,980 --> 00:05:31,510 packets and so forth. 70 00:05:31,540 --> 00:05:38,740 IP does not provide those features and relies on higher layer protocols to implement those features. 71 00:05:39,760 --> 00:05:43,660 So let's look at the format of an IP version for address. 72 00:05:43,750 --> 00:05:51,550 An IP version for address is 32 bits in size, normally written in dotted decimal notation such as this 73 00:05:51,550 --> 00:05:54,730 example 10.1 1.1. 74 00:05:55,120 --> 00:05:59,380 Each of value such as ten is eight bits in size. 75 00:05:59,560 --> 00:06:09,760 So in other words, we have x x x x with each x being eight bits in length, also known as an octet. 76 00:06:10,120 --> 00:06:13,180 The total size of the address is 32 bits. 77 00:06:13,210 --> 00:06:15,320 Please refer to the binary video. 78 00:06:15,340 --> 00:06:21,550 If you're not sure about bits and how to convert this address into binary and back again. 79 00:06:21,970 --> 00:06:28,480 IP addresses once again have a hierarchical structure to enable routing, which consists of two main 80 00:06:28,480 --> 00:06:29,260 parts. 81 00:06:29,380 --> 00:06:35,440 We have the network portion of an address and the host portion, and we'll look at that in more detail 82 00:06:35,440 --> 00:06:36,520 in a moment. 83 00:06:36,850 --> 00:06:45,520 IP addresses are used for routing in a very similar way to the way DHL or FedEx route parcels based 84 00:06:45,520 --> 00:06:47,320 on a destination address. 85 00:06:47,380 --> 00:06:53,950 Routers will route traffic to a destination address when unicast packets are transmitted. 86 00:06:54,160 --> 00:06:59,250 Multicast packets use a different mechanism and do their routing based on source address. 87 00:06:59,290 --> 00:07:08,350 So as an analogy, DHL or FedEx are sending the parcel to a destination based on the destination on 88 00:07:08,350 --> 00:07:09,430 the parcel. 89 00:07:09,430 --> 00:07:16,330 Routers are sending packets to destinations based on the destination address in the packet.