C’est quoi un serveur DNS et quel en est son rôle ?
Nous allons aborder ici un serveur dont le rôle est essentiel dans Internet, je veux parler bien évidemment du serveur DNS. Vous verrez qu’il est utilisé partout sans forcément que vous vous en rendiez compte.Comme d’habitude pas de termes trop compliqués, je vais vous donner une définition du DNS expliquée de façon simple et répondre aux questions : « C’est quoi un serveur DNS et quel est son rôle ? ». Et pour terminer, nous aborderons également le lien avec le domaine.
Définition et rôle du DNS
Tout d’abord : DNS veut dire « Domain Name System » ou système de nom de domaine. Je vais tout d’abord vous expliquer le fonctionnement, puis nous aborderons la notion de nom de domaine (ou de sous-domaine).
Pour vous expliquer, le rôle et le fonctionnement d’un serveur DNS, je vais reprendre l’exemple du téléphone.
Vous souhaitez appeler quelqu’un dont vous ne connaissez pas le n° de téléphone ?
Que faites-vous ? ….
…. vous utilisez un annuaire !
Et bien voila, un serveur DNS est un annuaire pour ordinateur. Lorsque vous voulez accéder à un ordinateur dans le réseau, votre ordinateur va interroger le serveur DNS pour récupérer l’adresse de l’ordinateur que vous voulez joindre. Une fois, que votre ordinateur aura récupéré l’adresse du destinataire, il pourra le joindre directement avec son adresse IP.
Le serveur DNS va permettre de faire la relation entre nom d’ordinateur et adresse IP. (ramené au téléphone, on obtient : nom de l’abonné et n°).
Vous allez me dire :
» mais je ne cherche jamais à joindre un ordinateur dans le réseau ! «
A quoi, je vais vous répondre :
» bien sur que si ! «
» Actuellement vous lisez ces lignes qui ne sont stockés pas sur votre ordinateur, donc votre ordinateur s’est connecté à un serveur pour récupérer les pages qui sont affichées sur votre écran. «
Exemple
Reprenons en modèle ce que vous avez fait pour arriver sur cette page, et regardons comment le serveur DNS est intervenu sans que vous le sachiez.
Vous avez lancé votre navigateur Internet et vous avez « www.google.fr » comme moteur de recherche par défaut. Donc la page google s’est affichée. Voici le mécanisme complet et regardez à quel endroit le serveur DNS est appelé.
Dans l’exemple ci-dessus, on voit que la requête « quelle est l’adresse de www.google.fr » a répondu 74.125.230.248. Cette requête s’appelle une résolution de nom de domaine.
Si l’on poursuit, on peut constater que le serveur DNS n’est utilisé que sur la partie 1-Question et 2-Réponse. Une fois que l’ordinateur a récupéré l’adresse du serveur à joindre, il n’a plus besoin du serveur DNS.
Cette adresse IP n’est pas une adresse au hasard. Elle correspond bien à un des serveurs de Google. (il y en a évidemment un grand nombre). Donc, si dans votre dans la barre d’adresse de votre navigateur, vous tapez : http://74.125.230.248, la page de recherche de Google doit s’afficher.
Attention, cela fonctionne à l’heure ou j’écris ces lignes, mais ce ne sera peut-être pas le cas au moment ou vous les lirez. (le serveur 74.125.230.248 sera peut-être éteint ? ou affecté à de nouvelle tâches ?)
Pour faire le test vous cliquer sur : http://74.125.230.248
NB du 05/01/2016 : Comme je vous le disais au-dessus, l’adresse peut avoir changé, et c’est le cas : Essayez maintenant avec http://74.125.206.94
Et chez moi ?
La plupart des personnes ignorent cette notion est c’est bien compréhensible. Alors comment cela peut-il fonctionner chez moi puisque je n’ai jamais renseigné ces serveurs ?
Les serveurs DNS fonctionnent en cascade. Pour expliquer cela on pourrait dire que lorsque qu’un serveur ne connait pas la réponse, il va demander à son « parent »
Chez vous, le serveur DNS est votre box (sauf si vous avez renseigné autre chose), et si votre box ne sait pas répondre, elle va interroger son parent : le(s) serveur(s) DNS de votre fournisseur d’accès. Cela peut remonter comme ça jusqu’aux serveurs racines. (on va dire pour simplifier que les serveurs DNS racines sont les serveurs de base du système : on ne peut pas remonter plus haut.)
La configuration DNS de votre ordinateur (ou tablette, et tout autre équipement connecté chez vous) est fournie par le serveur DHCP.
Un fichier
Peut-être en entendrez vous parler si vous travaillez dans l’informatique (ou si vous bricolez un peu). Un fichier présent sur la machine peut remplacer les requêtes DNS.
Ce fichier est le fichier « host » (hôte en français). Il va contenir la correspondance entre les adresses demandées et les adresses IP. Sur chaque ligne de ce fichier on va retrouver au début l’adresse IP suivi d’un espace ou d’une tabulation et ensuite du ou des nom(s) correspondant à cette adresse. Exemple : 74.125.230.248 www.google.fr
La sécurité
Parlons juste un peu de sécurité.
Pour bien comprendre de quoi je veux parler, je vais reprendre l’exemple du téléphone :
Imaginez que vous ayez entre les mains un faux annuaire (piraté) ou les numéros de téléphone ne soient pas les bons, et vous renvoie vers des pirates.
Vous ayez besoin d’appeler votre banque : Vous appelez le numéro de téléphone et vous allez forcément tomber sur des pirates (mais vous ne le savez pas).
Au bout du fil, on peut vous demander des informations confidentielles, et vous les donnerez en tout confiance !!!
Il faut bien comprendre que cela peut être pareil avec des serveurs DNS et qu’il existe des virus qui modifie vos paramètres réseaux ou votre fichier « hosts » pour faire pointer les requêtes DNS vers des serveurs pirates.
Une des blagues des administrateurs réseaux est de modifier, au sein de l’entreprise, une des entrées DNS d’un site vers un autre site. (Par exemple : faire pointer Facebook vers le site des Tortues Ninja ! : ainsi chaque fois que quelqu’un voudra aller sur Facebook, il se retrouvera sur le site des Tortues Ninja)
Changer de DNS
Sachez qu’il est tout à fait possible de changer de DNS. Lorsque vous utilisez votre connexion Internet, les adresses des serveurs DNS sont généralement ceux de votre FAI, mais sachez qu’il est possible d’en changer. Vous trouverez ci-dessous des sites proposant des listes de serveurs :
et je peux également vous en donner 2 très connus :
OpenDNS : 208.67.220.222 et 208.67.222.220
Google : 8.8.8.8 et 8.8.4.4
Pourquoi changer de DNS ?
Je vois 2 raisons principales pour changer de DNS :
Si vous avez peur d’être « espionné », (car un serveur DNS) sait exactement quels sites vous consultez, mais il peut également vous renvoyer vers les sites qu’il a choisi.
Si vous trouvez votre accès un peu lent, (car rappelez-vous un serveur DNS est appelé à chaque page consultée) et plus il mettra du temps à répondre, plus la page mettra du temps à s’afficher.
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However, as the head of the family, you must not panic at this time.This strength is really good. Looking at your young age, you should also be a young talent.
He is as fierce as a sword fairy. Boy, you are courting death Seeing Lin Xuan approaching step by step, the bald man was completely angry.It can be said that no one would rather offend Bloody Hand than provoke this Ghost Li.
Obviously, this is also a swordsman. The other person was calm and unrestrained, like an exiled immortal.Whose elder do you dare to rely on your old man in front of me You are looking for death.
Fortunately, as long as Tian Youque doesn t enter, then everything will be easy to handle.Yeah, these people are too powerful, they can kill us in an instant, if they attack suddenly and we don t activate the formation, then it s really over The faces of the Ninth Elders and the two were ugly.
It is not a good thing that someone can escape the king s killing array and attack them.But this time, she was wrong. Because Lin Xuan is not from the Daxuan Empire at all.
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At this time, the mysterious venerable said in a deep voice Don t worry, we won t spare that kid.What did you say to send us to hell The two people in front sneered disdainfully.
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The bald man grinned after hearing this Don t worry, our Heifengtang can handle this matter.When the sword arrived at the rushing sword energy, the black dragon leader finally changed his face.
Don t worry, this matter is on me. Shen Linchuan said with a smile I don t know when the auction will be, but I want to go and see it.For a moment, all the eighteen venerables in the hall died, leaving only the last evil young man in white shirt.
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This is a ground level exercise, and it is a ground level exercise that increases body strength and qi and blood.
When Lin Haoming heard that, he felt that the old dragon king really had a heart like glass.The current queen mother has two sons. After Wei Nao became king, Wei Hong s status has also risen.
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In the silent hall, everyone looked at the high majesty, but no one spoke.A few people soon discovered that the person who rushed back was led by Che Xun, the battalion commander of the law enforcement battalion in the army, who was also Wei Kang s nephew.
He thought that the two people still survived. Both of them are very young, the woman is in her seventies, and the man is a little younger than two or eight years old.A few days after leaving, Lin Haoming specially summoned all the people from Li Jinguang and Sujuanzhili, which can be regarded as a gathering after the first departure, but when the Xiao family came one by one, an unexpected person appeared He followed Lin Haoming.
Any 4471 Navigating The Waters Potential Side Effects Of Cbd Gummies movement of troops requires With the agreement of the elder and I, the elder Qinghang is retreating, and you have to inform me.Since he took refuge in him, he would not hide it, which would make it easier to get along with him in the future.
Even though the chance is a bit despicable, I like it.On the contrary, these people who awakened the so called bloodlines gradually became the actual rulers of that world, but the cultivation base of Lin Haoming and others is also the same.
He Wanfeng originally blamed his elder brother in his heart, but when he saw that his elder brother was ridiculed because of him, his face turned red and pale with anger.Of course, spreading incense for your Finding The Best Sleep Gummies Uk For A Restful Nights 0750 Sleep Oibzq wife is not a problem.
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Lin Haoming said. He is going to be a king now, and he was very bad after that, why did he become firm after seeing you Lin Haoming asked with a smile.Lin Haoming also nodded in satisfaction, and chose one at random.
It happened like this. What made Feng Shijian even more ridiculous was that Wang Guifei and Wei He had already fled for a day, and it had been three days since the last time this Majesty saw the courtiers, and no one thought that something was wrong.After all, practitioners don t need general supplies, and they can sleep without sleep for ten days and a half months.
On the contrary, they despise us in the south of the mountain and regard them as barbarians, so the state of Wei and Other countries are different, brother in law means, they will never have such a good life.Why did he go to the guard Lin Haoming asked again.
He needs to make some other records here. That s what he needs to worry about.On top of this, Lin Haoming felt helpless, the four star mission, the restrictions imposed on him by the spirit ring were even weaker.
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This gray light wave was naturally emitted by Sky Youque, who was frantically devouring the spiritual power around him at this moment.This is the gorgeous dividing line The fire dragon surrounded, dispelled the gray mist, and then brought back the fainted disciples.
I can guarantee that after absorbing it, your strength will definitely be greatly improved, but you will never be able to condense into the realm of kings in your life, let alone hit a higher level.But what surprised Lin Xuan was that You Que s physique was so strong that day, he had chopped so many swords, but none of them hurt him.
When Yan Feng saw this scene, the corners of his mouth slightly raised, with a confident smile on his face, and then He stretched out his big hand and grabbed one of the swords.He didn t expect that three small human reptiles could escape from his hands.
They don t need to think about it, they also know that there is a very terrifying formation ahead.This Lin Xuan is so arrogant that he even dared to contradict the Shenjian Villa.
More than half a month later, Lin Xuan and his party came to Tianfeng Kingdom.Otherwise, you will never even think about leaving Tiannan Territory and Tianwu Continent in your life.
She has a beautiful face, like a fairy, holding a fluffy little fox in her arms, unexpectedly there are nine tails.Murong Qingcheng and Luo Bingshan were already familiar with this language, but if it was replaced by anyone else, even the king would vomit blood when he heard Managing Blood Sugar Levels With Hemoglutrix Blood Sugar Gummies Amazon Enlgu 34 these words.
However, Lin Xuan was quite confident Don t worry, I won t make fun of my own life.At this moment, everyone s face was full of despair.
Although this attack was not powerful enough, judging from the aura, those who didn t know thought it was an attack from the king.Earth level skills are also divided into four levels upper, middle, lower, and top.
And Lin Zhan also waved his palm, stuffed a bunch of elixir into Lin Xuan s How To Make Cbd Gummies At Home Easy Steps For Beginners 63 arms, and then said in a deep voice, recover quickly, I will deal with him.However, the other party broke his illusion in the blink of an eye, which directly overturned his cognition.
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From the beginning to the end, he did not show any dazzling martial arts, nor did he emit any bright light.a king. It can be said that there is almost no one under the king who can compete with him, but now, he was defeated by a punch.
Soon, these people were divided into five teams, each with ten people, charging in different directions.Looking at it, the forbidden area of life is indeed extremely terrifying, but I don t know where You Que got this Nine Nether Demon Sword from today.
But at this time, the dark red dragon beside him couldn t stand it anymore, and it finally made a move.After all, it s fine if it s an ordinary place, but now there is an extremely terrifying Sky Youque in front of it, who knows what terrible things will happen.
That s fine. Seeing that the other party didn t have any bad intentions, Lin Xuan nodded.They naturally recognized each other, this is a famous celestial girl in the mainland, her reputation is not weaker than the fourth son of Tianwu.
Although there were cracks under Tian Youque s attack, this formation seemed to be able to repair itself, and those cracks only existed for a short time before returning to normal.Moreover, his current strength is not enough to compete with the opponent.
Shen Xia asked questions in succession, with a look of contempt.However, for the sake of safety, Lin Xuan did not drive the spirit boat to the Nanhuang Mountain Range, but stopped near the Nanhuang Mountain Range.
This is the gorgeous dividing line He was chasing the two old men of the Zhao family, while the dark red dragon flew towards the warriors of the Dong family.It was not until today through everyone s discussion that the whole thing was completely spread.
The terrifying sound resounded in all directions, and many martial artists around were bleeding from their ears, and kept retreating.On the other hand, Lin Xuan was full of fighting spirit, his momentum was like a rainbow, he was surrounded by sword lights, and his whole body was full of murderous aura.
If it really doesn t work, he can also control the Myriad Beast Cauldron, which is his biggest trump card.I don t believe you won t come out. Hehe, just because you still want to stop me, if I want to leave, even the king of heaven can t stop me.
Okay, here you are. In a certain grand canyon in the northwest, I can show you the exact location.Boy, you are crazy and dare to kill the people in our Nether Hall.
They ran in different directions and could definitely escape.Damn it, how is this possible, what method did he use A look of panic appeared in Tian Youque s eyes, after all, What Do 501 Cbd Edible Gummies Do Benefits Effects Usage Guide the Cangsong sword cast a great shadow on him back then.
The next moment, Luo Bingshan s jade face was very cold, and her gaze was even more icy looking forward, then she froze, and even a hint of shock appeared in her brows.Because it is different from what he imagined, it is not a ready made battle armor, but a small stone like a star.
Hmph, I don t know how to live or die. Lin Xuan snorted coldly, with a murderous intent in his eyes.However, they didn t have any joy, and even a sense of panic emerged in their hearts.
Everyone was shocked and couldn t believe it. Elder Linghu was even more stunned.Like the five thousand year old Zilei Protoss, they can be used to make earth level weapons.
Now that Lin Xuan is added, it will be even more invincible, so it can only beg for mercy.On the left was an old man in green robe, holding a long knife as thin as a cicada s wing, and quickly slashed towards Lin Xuan.
Hmph, how dare a group of ants act wildly in front of me Duan Fei was very disdainful, and when he lifted his finger, several cold lights flew out like lightning.Lin Xuan also seemed to have become silent. He was always trying to get out, but he had tried all of those methods, and none of them succeeded.
Two beautiful maids poured the spiritual tea, and then stood aside respectfully.Why do you say that the nine tailed demon fox has not left This time it is the turn of the ancestor of the Shen family.
Apologizing Lin Xuan sneered, you have found the wrong person Hearing this, the red haired young man hurriedly climbed up in front of Murong Qingcheng and began to kowtow.Netizens please remind Please pay attention to rest your eyes when reading for a long time.
Now that they got the key, everyone left Xingchen Pavilion, and the next thing they had to do was to wait for Tian Youque.But Lin Xuan let out a low growl, the dragon sword field flickered all over his body, and a shocking sword Vigorvita Cbd Gummies Benefits Reviews 261 And Expert Opinions light shot straight into the sky, tearing open the entire void.
