1 00:00:00,970 --> 00:00:01,640 Welcome back. 2 00:00:02,110 --> 00:00:09,910 Before we proceed with scanning, I just want to give a basic overview of DCP and UDP protocol for anyone 3 00:00:09,910 --> 00:00:12,190 that is encountering it for the first time. 4 00:00:12,970 --> 00:00:16,090 We already mentioned what TCP and UDP are. 5 00:00:16,460 --> 00:00:22,510 They are two different protocols used for sending bits of data or also known as packets. 6 00:00:23,290 --> 00:00:27,410 DCP and UDP are not the only protocols that are out there. 7 00:00:27,550 --> 00:00:30,130 However, they are the most widely used ones. 8 00:00:30,820 --> 00:00:32,470 Let's talk about DCP first. 9 00:00:33,100 --> 00:00:40,630 So DCP stands for Transmission Control Protocol and it is the most commonly used protocol on the Internet. 10 00:00:40,990 --> 00:00:47,080 When you load a webpage, your computer is sending DCP packets to the Web server address, asking it 11 00:00:47,080 --> 00:00:48,400 to send a Web page to you. 12 00:00:49,000 --> 00:00:55,180 Then the Web server responds by sending a stream of DCP packets, which are Web browser stages together 13 00:00:55,570 --> 00:00:57,490 to form the Web page that you see. 14 00:00:58,090 --> 00:01:04,360 The same happens once you, for example, click on a link or Sinding or post a comment on your Web browser, 15 00:01:04,360 --> 00:01:08,870 sends DKP packets to the Web server and the server sends DSP packets back. 16 00:01:09,190 --> 00:01:12,790 However, this is not a one way communication. 17 00:01:13,390 --> 00:01:18,030 The remote system sends packets back to acknowledge that it received your packets. 18 00:01:18,490 --> 00:01:22,420 So this is based on three way handshake. 19 00:01:22,870 --> 00:01:28,270 And as the name says, three way handshake is consistent out of three steps. 20 00:01:29,020 --> 00:01:32,440 First one is sent in the step. 21 00:01:32,440 --> 00:01:35,380 The client wants to establish a connection with the server. 22 00:01:36,130 --> 00:01:38,310 So it sends a segment within. 23 00:01:38,770 --> 00:01:46,690 And what sin stands for is synchronize sequence number, which informs server that client wants to start 24 00:01:46,700 --> 00:01:51,220 communication and with what sequence number eight starts the segments with. 25 00:01:52,560 --> 00:01:59,130 After the same step comes the Cenac, which is the second step, and in the step, the server responds 26 00:01:59,130 --> 00:02:05,910 to the client's request with Sinak signal, which set back signifies the responsive segment it received 27 00:02:06,300 --> 00:02:08,910 and seen, is the same from the first step. 28 00:02:09,150 --> 00:02:15,930 It signifies with what sequence number it is going to start this segment with in the third and final 29 00:02:15,930 --> 00:02:17,970 step, which is just ekh. 30 00:02:18,450 --> 00:02:24,390 In this step, the client acknowledges the response of server and they both establish a reliable connection 31 00:02:24,630 --> 00:02:27,030 with which they will start the actual data transfer. 32 00:02:27,870 --> 00:02:33,680 This is just an example of DCP communication establishing between a client and a server. 33 00:02:34,290 --> 00:02:41,580 Once the data transfer starts, DCP guarantees the receiver will get the packets in order by numbering 34 00:02:41,580 --> 00:02:41,760 them. 35 00:02:42,360 --> 00:02:48,450 Then the server sends messages back to the sender, saying it received the messages or packets. 36 00:02:49,080 --> 00:02:54,750 If the sender does not get the correct response, it will resend the packets to ensure the server got 37 00:02:54,750 --> 00:02:55,320 the packets. 38 00:02:55,950 --> 00:02:58,220 All of those packets are also checked for errors. 39 00:02:58,710 --> 00:03:06,510 So TCP is all about reliability packets and with DCP are tracked, so no data is lost or corrupted in 40 00:03:06,510 --> 00:03:07,010 transit. 41 00:03:07,440 --> 00:03:13,260 That's why once you download the file, for example, over the Internet, your file is working once 42 00:03:13,260 --> 00:03:19,050 you run it in your machine because it is being transferred with DCB, so all the packets will reach 43 00:03:19,050 --> 00:03:21,300 their destination without any errors. 44 00:03:21,900 --> 00:03:29,670 Euterpe, on the other hand, stands for user data protocol and data is the same thing as a packet of 45 00:03:29,670 --> 00:03:30,270 information. 46 00:03:30,600 --> 00:03:37,170 And UDP protocol works similarly to Tsipi, but it throws all the error checking stuff out. 47 00:03:37,530 --> 00:03:39,570 That's why UDP is much faster. 48 00:03:40,170 --> 00:03:44,670 It is used when speed is desirable and error correction is not necessary. 49 00:03:45,060 --> 00:03:49,740 For example, UTP is frequently used for live broadcasts and online games. 50 00:03:50,220 --> 00:03:56,940 That's why UDP doesn't really care whether packets received its destination and it will not send the 51 00:03:56,940 --> 00:03:57,480 packet. 52 00:03:57,480 --> 00:04:02,040 If it didn't reach the other part, it will just continue sending other packets. 53 00:04:02,640 --> 00:04:05,660 You cannot ask for those packets again with would. 54 00:04:06,240 --> 00:04:10,770 And these are just the basics behind to most known protocols for communication. 55 00:04:11,460 --> 00:04:16,350 Even though many of you probably knew this already, it is good to have a refresher since we're going 56 00:04:16,350 --> 00:04:18,720 to need this knowledge once performing, scanning. 57 00:04:19,110 --> 00:04:20,040 See you in the next video.