TCP/IP

The internet makes it possible for one computer in one place to talk to 0:00 another computer in a completely different place, but it hasn't always been this way. 0:04 in the mid 1970's and early 1980's, the set 0:09 of protocols that enables computers to talk to each other was being developed. 0:12 The sending and receiving of data on the internet 0:17 was made possible by two protocols, TCP and IP. 0:20 TCP is the transmission control protocol and it splits data up into packets and 0:24 puts them back together again at their destination. 0:30 IP, the internet protocol, tells the packets where to go and 0:33 to where they should return. 0:37 Let's see what this looks like. 0:39 The things you get from the internet, like an HTML page or a YouTube video, and 0:41 the things you send over the internet, like an e-mail to a friend, are all data. 0:46 In order for data to be sent over the internet, 0:51 it needs to be broken into packets. 0:53 A packet isn't an entire web page, or even usually a whole e-mail. 0:56 It's a small chunk of data, like a puzzle piece of the whole picture. 1:00 By breaking data into these small, 1:04 manageable chunks, many users can transmit data at the same time very quickly. 1:06 In essence, these packets are a way of sharing access to the network, so 1:12 that no single transmission dominates the pipeline. 1:16 The TCP/IP Protocol Suite is responsible for creating packets, making sure they get 1:20 where they need to go, and putting them back together again at their destination. 1:26 If something gets lost along the way, TCP will request the packets to be resent. 1:31 The directions on how to accomplish this are written in a header and 1:37 wraps every TCP packet. 1:41 Once TCP makes a packet and wraps it with header, the packet is handed off 1:44 to the next layer which will handle the details of how to transmit the data. 1:49 Now every computer on the internet can be identified by its own unique number called 1:54 an IP address, and the IP protocol uses IP addresses to route the TCP packets. 1:59 In order to transmit the data to the correct location, the IP protocol 2:07 also adds a small header of information to the packet, just like TCP. 2:11 The IP header contains information on how to send the packets, 2:15 such as the source IP address and the destination IP address. 2:21 Now, because packets often travel through a number of routers on their way to their 2:25 final destination, to make this process really fast, 2:29 each packet is designed to work independently. 2:33 This means that each packet can travel from router to router in 2:37 the fastest way possible to reach its destination. 2:40 When all the packets are received, 2:44 TCP will reassemble them, making sure they're all there and in the right order. 2:46 Now that we understand a little bit more about how the TCP/IP Protocols get 2:51 data from one place to another, let's find out about the other pieces of hardware and 2:55 software used to bridge the distance between computers. 3:00