https://blog.csdn.net/hjding/article/details/80301389
Internet protocols: TCP / IP protocol suite.
Ethernet protocol
For example, there is a LAN technology has been called "Ethernet", so good, on the Internet runs on Ethernet, English writing:
TCP / IP over Ethernet
Note: TCP / IP is designed for the development of a series of agreements among Internet the two agreements, because these two protocols most important (and most famous), these two agreements on the use of the Internet to speak.
There is also a metropolitan area network technology called "token ring", so good, the Internet will run on Token Ring, writing in English:
TCP / IP over Token-Ring
there is a wide area network technology called "ATM", then well, the Internet is run on top of ATM, writing in English:
TCP / IP over ATM
if you want to run on USB Internet it? Nature is:
TCP / IP over the USB
The OSI 7 layers model, IP, TCP and third layers respectively four, Internet protocol suite does not cover the full layer 7, it is clear that there is no defined shape Internet crystal head, there are a few copper cable, copper which and so is the number of voltage transmission parameters, such as an Ethernet network is defined.
Ethernet defines only two layers 1 (physical layer, data link layer), IP, and TCP define the 3,4 Layer 3 (network layer, transport layer), a protocol (such as FTP) and then further on existing Internet, there are other companies, some higher-level protocols (such as SQL, JPEG,
HTTP) ----------------
Disclaimer: This article is the original article CSDN bloggers "Qiantang Wuji", and follow CC 4.0 BY -SA copyright agreement, reproduced, please attach the original source link and this statement.
Original link: https: //blog.csdn.net/hjding/article/details/80301389
I speak from my understanding of it {excerpt knew almost Daniel, I will read it again a}.
For example: We know that, for historical reasons, there have been many countries and nations in the world, they all use different languages.
For example, to communicate and French must learn French, Japanese and the Japanese must learn to communicate, empathy, to learn German, Italian, Spanish. . .
If every country and communications must learn each other's language, then it had better exhausted.
Therefore, the best way is to use one kind of language we all communicate. So just have to learn a foreign language can communicate with all of the country.
This "universal language" can be obtained by two kinds of ways: readily available, and new inventions
after the industrial revolution, the sun never sets empire center of the world, the United States is the center of its direct successor of the world, they are all in English, so English With its strong position as the world's universal language.
Meanwhile, the "Esperanto" is also a universal language, unlike English, Esperanto is the language of the "new invention" (of course, also draws on other rules of the language), that is to say, no nation is "Esperanto nation" nor It may be found in front of a stone somewhere in 1000, engraved on Esperanto. . .
Because the state is not a native language Esperanto, so when Esperanto exchanges must go through a "translation" process: the native language, translated into Esperanto.
So we can say that Esperanto is a "rootless" language, is an "incomplete" language, it must rely on the use of other languages in order, or: to run on top of other languages.
For historical reasons, "computer network" from scratch, from small to large developed.
There are many network was invented. Some networks only apply to a small area, such as a home, a building, the line length is calculated by the meter, meters. Such a network is called "local area network"
Some networks used in a large area, for example, I go through broadband, there is a kilometer-long line between so I N and telecommunications companies, or have between telecommunications companies and telecommunications companies up to several ten kilometers of lines. Such networks called "wide area network." These networks use their own protocol (language), incompatible (different languages can not understand each other),
in order to achieve a unified network in the world, so that these incompatible networks to communicate with each other, in order to establish a "Internet" , we all need to use the same protocol.
Hero, there was such an agreement, called "Internet Protocol" (also known as TCP / IP protocol).
Internet Protocol is the "network Esperanto", regardless of your network's proprietary protocol is how strange, external communications and all of them use TCP / IP. Because the native protocols of the Internet protocol is not these networks, so a variety of network must have a "translation" of the process: the protocol Ben Wang, translated into Internet protocol.
As said above, Esperanto is not a "native language" of any nation, so we need to use a translation of Esperanto. And this translation process, the reason is the MAC address exists, and detailed below.
Before the advent of the Internet has been a lot of network appeared, but the Internet is not the first global network (obviously, the historic wired telephone network is the global network)
then, the Internet appeared.
It should be noted that the Internet was born at the beginning and did not think he would become a big global network, so there is no design for the characteristics of the global network, which left some shortcomings (such as IP address is not enough, there are loopholes in the agreement, think of the famous ARP protocol vulnerabilities. after the success of the Internet, these vulnerabilities are IPV6 make up).
Internet design original intention was to deal with nuclear war against the Soviet Union (then the Soviet Union still exists).
You may have heard of "balance of terror" concept, saying that the Soviet Union either party to the other party if pre-emptive nuclear war, the other nuclear retaliation will let himself in flames, so no one dared to use nuclear weapons first in order avoiding nuclear war.
But it is clear that only "equal skill" to appear "balanced" if we "one's opponent" has the ability to win a nuclear war, it can put ridiculous "balance" thrown into the Pacific Ocean.
US Department of Defense (DoD) thinking:
I threw a bomb to the Soviet Union, the Soviet military command and communication system to collapse, and there is no command, no matter how powerful army has become without a head, there is no fighting.
The Soviet Union to the United States can throw a nuclear bomb, the United States will have the same outcome.
but. . . If I were to design a communications network structure that "disaster" of very good, very "robust", very "high-availability" of a Soviet nuclear bomb can not destroy, two nuclear bombs can not destroy, three bombs before they can off. I am a nuclear bomb could destroy it. So I have room to breathe, I could be the winner of a nuclear war.
Under this thinking is that the Internet was born.
Internet can resist nuclear explosion? What really so magical? Look at Figure know.
Let us talk about the traditional telephone network topology:
<img src="https://pic4.zhimg.com/50/7e6a71596fd61bf84b8840605ad7c726_hd.jpg" data-caption="" data-size="normal" data-rawwidth="487" data-rawheight="453" class="origin_image zh-lightbox-thumb" width="487" data-original="https://pic4.zhimg.com/7e6a71596fd61bf84b8840605ad7c726_r.jpg">
Telephone network is a typical star network, users give the user F A call its path is the AKF
Similarly, the user C G to give users call path is the CKG
In other words, between any user to call, they are inevitable to go through a central switch K
So you know why at the time of war, the bureau is the primary target, because the bureau which stood a telephone exchange. If you want to destroy the city's telephone network, I do not have to send troops went door to door to drop the phone, as long as the bureau's telephone exchanges destroyed, everything is OK!
How to prevent this from happening then that's it? The traditional theory of war is this thought:
Scheme A, I hide the location of the switch, so that the enemy can not find where it is.
But the modern battlefield, sky satellite, underground monitoring, monitoring network in the face of tight, want to hide myself up, it is no easy task.
That plan B, I arranged heavily around the switch, the construction of fortifications, even if you have found the attack does not come.
But the great power of modern weapons, coupled with nuclear weapons, more people, then it is difficult to resist the strong fortifications.
Clearly, because of the emergence of modern weapons, modern warfare theory have to follow up.
So thinkers brains, another way to make a fuss about the network topology, to "centralized" to "distributed", created out of the Internet.
What the Internet has taken way to avoid being attacked core equipment, so that the network can survive longer in war time?
The method is this: there is no core equipment!
See the following figure:
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It can be seen from the star topology network, a mesh network becomes.
Here each user (or node) is a telephone exchange (for the Internet, is the router)
At this point, if A and H phone, that path can be more:
The shortest distance is certainly AH, so take priority AH.
But if AH is broken, you can also go ADH, AEH, AEFBDH. . . .
So, AH nothing broken, BC cut off all right, CD off all right, FG off all right. . .
Thus, the mesh network is a very "high-availability" of the network, disaster recovery is very good.
The status of these nodes (functions) are the same, a node is more important than the other nodes absence. So a node out of the question, additional nodes can be replaced.
The star network is not the case, it is clear that the central node is more important than other nodes, the central node fails, other nodes can not be replaced, the entire network becomes ineffective.
As the number of nodes increases, the number of available lines between nodes increases exponentially embodiment, the function is N * (N-1) / 2.
This simple function but a great power, to borrow online Photo:
<img src="https://pic4.zhimg.com/50/v2-f45e545c7aeaa45c28f0a1179e63ea40_hd.jpg" data-caption="" data-size="normal" data-rawwidth="663" data-rawheight="675" class="origin_image zh-lightbox-thumb" width="663" data-original="https://pic4.zhimg.com/v2-f45e545c7aeaa45c28f0a1179e63ea40_r.jpg">
Compared to the star network, if you want to destroy such a mesh network, how to start it?
Internet was originally defense communications network (APRA- ARPANET), later changed to connect universities, government departments and research institutions of teaching and research network, and finally evolved into a money-losing business network.
The above mentioned knowledge is called the "architecture of the Internet."
Let me say Internet Protocol: TCP / IP protocol suite
from the very beginning, the Internet is no thought has become a world wide net, so from the beginning of the development of the Internet protocol is "incomplete" in. In other words, the Internet must be based on other networks, relying on other networks to complete their function.
Like Esperanto is incomplete, it must be based on other languages in order to achieve its own function.
If running on Chinese Esperanto, then writing:
Esperanto over Chinese
For example, there is a LAN technology has been called "Ethernet", so good, on the Internet runs on Ethernet, English writing:
TCP / IP over Ethernet
Note: TCP / IP is designed for the development of a series of agreements among Internet the two agreements, because these two protocols most important (and most famous), these two agreements on the use of the Internet to speak.
There is also a metropolitan area network technology called "token ring", so good, the Internet will run on Token Ring, writing in English:
TCP / IP over Token-Ring
there is a wide area network technology called "ATM", then well, the Internet is run on top of ATM, writing in English:
TCP / IP over ATM
if you want to run on USB Internet it? Nature is:
TCP / IP over the USB
. . . . . . . . . . .
You must know the OSI 7 layers model, IP, TCP and third layers respectively four, Internet protocol suite does not cover the full layer 7, it is clear that there is no defined shape Internet crystal head, there are a few copper cable, voltage which copper is the number of transmission parameters, etc. these parameters are such as an Ethernet network defined.
So why the Internet does not define these parameters?
He says: "Maybe" From the beginning, the Internet did not think he would become a world wide net, so it does not define it so complicated.
But there is also another possibility: In fact, a network technology, do not have to "large", from one layer to the full seven-layer formulation, which can be developed only several layers.
1 such as an Ethernet defines only two layers (physical layer, data link layer), IP, and TCP define the 3,4 Layer 3 (network layer, transport layer), a protocol (such as FTP) further on the existing Internet, there are also some other company's higher-level protocols (such as SQL, JPEG, HTTP)
Thus, mutual cooperation between different networks, different protocols on it.
Like, I is a production train manufacturers, of course I can produce the tracks, the width of the tracks of the development, production train cars.
But since there are already a large number of rail laying is completed, that I do not control what the tracks, trains running on existing tracks on it.
Here, the track is Ethernet (LAN), ATM (WAN) or other existing Layer 2 network, the train is the Internet.
Therefore, the "pure Internet" never existed, because the Internet does not define the bottom, there is only TCP / IP over XXX.
After the above explanations, you will need to know why certain MAC address: the Internet does not exist Cui, also includes Ethernet.
Because the Internet is the third layer protocol, is no foundation for the "castle in the air", this need Ethernet Layer 2 network concrete floor implementation, while the MAC address is a two-layer concept, so the MAC address and thus entered the architecture of the Internet.
Ethernet MAC address format is 12 hexadecimal numbers, such as 0800200A8C6D
Internet IP address format is four decimal numbers separated by dots, such as 192.168.201.160
just said, "pure Internet" does not exist, it is necessary to Internet based on Ethernet to work, so that "while running two network"
like Esperanto have to be based on the Chinese to work, so that "two languages at the same time said,"
so, it must be "translated"
also the Ethernet MAC address is translated into the IP address of the Internet, this is the role of ARP
If my Chinese name is "Tao", if you want translated into Esperanto, Esperanto would certainly have a name (assuming that called LIUTAO)
The same is the name:
Liu Tao translated into → → LIUTAO
also address:
21-35-6D-1F-83-9E → translated into → 202.143.90.8
Of course, if the Internet began to develop from the beginning, it defines the protocol from the physical layer to the transport layer, the Internet is no longer dependent on any other network, then you do not have what the MAC address.
Finished.
I was not too wordy. . . .
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Disclaimer: This article is CSDN blogger "Qiantang Wuji 'original article, follow the CC 4.0 BY-SA copyright agreement, reproduced, please attach the original source and this link statement.
Original link: https: //blog.csdn.net/hjding/article/details/80301389