TCP vs UDP Who is more reliable TCP exists in the meaning of "Internet"

This article is only for the sake of understanding, to make a very broad description, the wording is not very rigorous, and the improper place is still correct, thank you. Before reading this article, I suggest that students who have little understanding of the OSI model TCP/IP should look at the vernacular I wrote before to explain the OSI model, TLS/SSL and HTTPS.

Everything in order to transmit UDP vs TCP

One of the reasons why the Internet is great is to solve the problem of reliable transmission of information over long distances. Since it is necessary to transmit data "mutually", there must be certain rules and protocols. TCP and UDP are two widely used transmission protocols. Make a simple comparison here:

UDP (you think of it as a plain mail), often the postman will focus on the post, such as a school post, but this method is not reliable, because this postal letter is always easy to "drop", also That is to say, this transmission method cannot ensure that the recipient will receive the letter.

This is not okay, so people think of a more reliable transmission method: TCP (you think of it as express), the courier can deliver directly to the door, even if you do not deliver the door, you can call you. Check your ID card, sign it, and so on, to make sure your package is not lost. Therefore, this method is more "reliable."

TCP vs UDP who is more reliable

The above example has also clearly seen that TCP (Express) is reliable because there are various "checking" mechanisms. When the "package" of the express delivery really reaches the recipient, this "transfer" process is only Completion is completed, otherwise the courier brother will "re-delivery". Then "UDP" (postal mail) does not care about this set, anyway, according to the address on the letter, the "transported mail package" is thrown in the nearest mail or the mailbox written on it, as soon as the package is not received. In the hands of people, this UDP does not matter.

So, until now, we know that TCP transmission data is more "reliable" than udp!

The meaning of TCP in the "Internet"

We can now read articles, live broadcasts, videos, entertainment, shopping, and even online transfers on the Internet. Of course, if you watch live broadcasts, the UDP protocol is still a good drop, but if it involves money or sensitive data, if it doesn't have a set of " "Reliable" transmission protocol, who dares to "transfer" online, "storage information"?

We already know that one of the meanings of TCP is: "Reliable transmission", but at the same time to carry out remote communication, "efficient transmission" is essential. Finally, the data packet travels through the sinister Internet." Secure transmission "is a must.

So, let's take a look at the fact that TCP has three meanings in the "Internet" (important things say three times): - Let the data be "reliable", "efficient", "safe" transmission - let the data "reliable", "Efficient", "safe" transmission - allowing data to be "reliable", "efficient", "safe" transmission

Please note: The "efficient" mentioned here is only relative to TCP itself, because this "efficient" will be related to the handshake of the second step of the three-way handshake, so I will mention here, in fact, UDP will be more efficient and faster than TCP because it does not have some detection mechanism.

a certain price

They all say that "fish and bear's paw can't have both". This is especially true for TCP. Since you have chosen "reliable", "efficient" and "safe" as your responsibility, you must think of ways to satisfy these characteristics. So what about TCP?

reliable

The reliability of the data means that the receiver has received accurate and correct information. If there is a packet loss in the middle, there must be a mechanism for the sender to resend. What about TCP? It does this:

The sender tells the receiver in a certain way how big the transmitted data packet is, and then divides it several times. For example, the data packet is 100kb in total, and then sent in 10 times. At this time, the receiver knows that there are 10 data packets in total and sends it at the same time. The party will mark the number on each data packet, and then TCP will accept it from packet 1, and add one by one. It knows that the tenth end is received. Only the 10 all acknowledges are received, and the receiver confirms that the communication is completed, so Ensure the reliability of the data.

Then the question comes, how does the receiver know that the data packet is 100kb, and then how do you know when to accept the packet? When is the acceptance completed? This is the beginning of the first handshake, and it can be said that it is the beginning of the first exchange.

For example: Zhang San (sender) should send a message to Li Si (receiver).

1. Zhang San: hi, Li Si, I want to send a 100kb packet, I plan to send it 10 times. Can you pick it up there?

2. Li Si: Ok, I received it, you send it.

3. Zhang San: Ok, great!

4. Zhang San: Data packet 1..2..3..4. .5..6..7..8..9..10