1 00:00:00,630 --> 00:00:04,710 The internet makes it possible for one computer in one place to talk to 2 00:00:04,710 --> 00:00:09,088 another computer in a completely different place, but it hasn't always been this way. 3 00:00:09,088 --> 00:00:12,160 in the mid 1970's and early 1980's, the set 4 00:00:12,160 --> 00:00:17,420 of protocols that enables computers to talk to each other was being developed. 5 00:00:17,420 --> 00:00:20,050 The sending and receiving of data on the internet 6 00:00:20,050 --> 00:00:24,900 was made possible by two protocols, TCP and IP. 7 00:00:24,900 --> 00:00:30,050 TCP is the transmission control protocol and it splits data up into packets and 8 00:00:30,050 --> 00:00:33,360 puts them back together again at their destination. 9 00:00:33,360 --> 00:00:37,350 IP, the internet protocol, tells the packets where to go and 10 00:00:37,350 --> 00:00:39,210 to where they should return. 11 00:00:39,210 --> 00:00:40,220 Let's see what this looks like. 12 00:00:41,280 --> 00:00:46,210 The things you get from the internet, like an HTML page or a YouTube video, and 13 00:00:46,210 --> 00:00:51,280 the things you send over the internet, like an e-mail to a friend, are all data. 14 00:00:51,280 --> 00:00:53,740 In order for data to be sent over the internet, 15 00:00:53,740 --> 00:00:56,220 it needs to be broken into packets. 16 00:00:56,220 --> 00:01:00,280 A packet isn't an entire web page, or even usually a whole e-mail. 17 00:01:00,280 --> 00:01:04,600 It's a small chunk of data, like a puzzle piece of the whole picture. 18 00:01:04,600 --> 00:01:06,470 By breaking data into these small, 19 00:01:06,470 --> 00:01:12,560 manageable chunks, many users can transmit data at the same time very quickly. 20 00:01:12,560 --> 00:01:16,890 In essence, these packets are a way of sharing access to the network, so 21 00:01:16,890 --> 00:01:20,820 that no single transmission dominates the pipeline. 22 00:01:20,820 --> 00:01:26,620 The TCP/IP Protocol Suite is responsible for creating packets, making sure they get 23 00:01:26,620 --> 00:01:31,720 where they need to go, and putting them back together again at their destination. 24 00:01:31,720 --> 00:01:36,710 If something gets lost along the way, TCP will request the packets to be resent. 25 00:01:37,830 --> 00:01:41,500 The directions on how to accomplish this are written in a header and 26 00:01:41,500 --> 00:01:44,310 wraps every TCP packet. 27 00:01:44,310 --> 00:01:49,280 Once TCP makes a packet and wraps it with header, the packet is handed off 28 00:01:49,280 --> 00:01:53,190 to the next layer which will handle the details of how to transmit the data. 29 00:01:54,630 --> 00:01:59,640 Now every computer on the internet can be identified by its own unique number called 30 00:01:59,640 --> 00:02:05,580 an IP address, and the IP protocol uses IP addresses to route the TCP packets. 31 00:02:07,150 --> 00:02:11,780 In order to transmit the data to the correct location, the IP protocol 32 00:02:11,780 --> 00:02:15,640 also adds a small header of information to the packet, just like TCP. 33 00:02:15,640 --> 00:02:21,130 The IP header contains information on how to send the packets, 34 00:02:21,130 --> 00:02:24,370 such as the source IP address and the destination IP address. 35 00:02:25,460 --> 00:02:29,770 Now, because packets often travel through a number of routers on their way to their 36 00:02:29,770 --> 00:02:33,580 final destination, to make this process really fast, 37 00:02:33,580 --> 00:02:37,000 each packet is designed to work independently. 38 00:02:37,000 --> 00:02:40,500 This means that each packet can travel from router to router in 39 00:02:40,500 --> 00:02:43,100 the fastest way possible to reach its destination. 40 00:02:44,220 --> 00:02:46,050 When all the packets are received, 41 00:02:46,050 --> 00:02:51,120 TCP will reassemble them, making sure they're all there and in the right order. 42 00:02:51,120 --> 00:02:55,760 Now that we understand a little bit more about how the TCP/IP Protocols get 43 00:02:55,760 --> 00:03:00,510 data from one place to another, let's find out about the other pieces of hardware and 44 00:03:00,510 --> 00:03:03,960 software used to bridge the distance between computers.