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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There will be no end, but you also decided to be more careful before.From the looks of it, the seven battalions in Lin Haoming s hands add up to nearly 1,800 people, which is really a lot.
Knowing this, Lin Haoming is even more sure about the old dragon king s protection of Taikang Mountain.The boat was made of wood, and the white wood seemed to be very soft.
After Lin Haoming said that, Hu Qianpeng suddenly smiled, then let go of Lin Haoming s chin, patted your face heavily, and said He is very stupid, just now he wants to talk One sentence is wrong, and now he is dead.Naturally, the city gate was closed and they couldn t enter the city, so the two of them planned to stay in a carriage and horse shop outside the city for those who couldn t enter the city to rest for one night, and then entered the city the next day.
He knows if people go, and there is no need for him to live.Your vitality is visibly deteriorating day by day, half a month Before, you looked the same inside and out as before, but Lin Haoming could tell that your feet were still a little weak, and it is estimated that you will need ten days and a half months to recover.
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Hearing that, several people nodded inwardly, and Wei Kang also asked proactively, Marshal lost his mind as soon as it was over You go in person.He has merit, is indeed good at fighting, and is from the royal family, and even Wei Nao wants to call him Uncle Wang, so Zhu Feiling feels a little tricky to choose this person.
Do you have talent under cultivation Whose potential does the mysterious fruit help people have nothing to do with cultivation.Although there was no seasoning, the fish under the pond soon gave off a scent, and Lin Haoming felt a warm feeling after eating it.
I win over Mrs. Ye Zi, and you win over Yu Kuan and Hong Xian, you are still at a disadvantage.Such a result made several people who followed Lin Haoming feel excited, while others looked at Lin Haoming with a look of no thought.
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When they arrived on the island, an old man with white hair and a childlike face and a fairy demeanor came over with some people.Hu Changgui stated his attitude and made up the difference by himself.
In this case, it was really the winter of previous years, but the first snow was ushered in first.With the current state of Jingguo, it is only a matter of time before the Ming Dynasty is destroyed, but now the Ming Kingdom is devastated and the people are withered.
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At this time, he reacted quickly enough, and immediately twisted his wrist and swung towards the back.It was full of bloody smell, and smelling this bloody smell, Lin Haoming himself felt that the blood in his whole body seemed to be boiling, and he tightly grasped the hand of the cold flame pearl, wanting to kill all the moving things in front of him.
Lin Haoming stared at the jade seal, and subconsciously felt that the jade seal was not simple.The number of temples will decrease greatly as you go to the back.
He also had to activate the evil armor again, so as not to be cheated by the means he used instead.I hope your preparations won t make us wait too long At this time, Shu Yue seemed to be a little impatient to wait.
As long as you advance to Nascent Soul, your path will be much smoother in the future, and you have a very close relationship with Lin Haoming.Near the Imperial Palace and Ancestral Temple, a Lingzhu Temple was built, in which the string of rosary beads given to them was enshrined.
Just when Lin Haoming was thinking, a childish but familiar voice suddenly sounded.Of course, the most important thing is that he really needs to absorb the real devil energy, otherwise he can just dodge and leave this position.
After all, he had never heard of the so called real spirit world and real demon world.Seeing such an astonishing blow, Lin Haoming did not choose to dodge again, but sacrificed the Tiansha sword again early, pouring all the evil energy into the Tiansha sword, and the gray light of the Tiansha sword itself was also released.
This is mainly because the middle realm is much more difficult to overcome than the small realm.At this time, Chi Xiao had already taken out the Heavenly Demon Token, and the Heavenly Demon Token released a ray of light to completely envelop him, as if he flew into this light gate when he entered the Heavenly Demon Pavilion Effectiveness Xvjy For Their Ed Investigating Cbd Blue Gummies before.
When he was caught seven inches from his neck, he continued to be stabbed with needles, his mouth grew wide, as if he was threatening the person who caught him.Since Xiaoxiao has already advanced to Nascent Soul, Zhuo Nishang It should be a lot of effort to help, and the founder of the Cailing Sect seems to be this kind of spirit body.
As a result, the female patriarch of the Meng family unexpectedly approached her nearby.After a few knots, and in a flash of light, it collapsed again.
In addition to the previous ones, the number is enough to raise the cold flame beads to a very high level.Seeing this scene, Lin Haoming was not only not very happy, but was slightly worried, but even so, he could only continue to control the cold flame bead to hit the iron pillar.
In fact, there were not only five families with golden core monks in the young contest, but other small and medium families nearby also participated, and four arenas rose above the open space.Lin Haoming s attitude, it s not that he, an emperor, has never seen it before.
The fastest update plus Lin Haoming, there are eight people in total, although Lin Haoming can tell that some of them know each other, but none of them are close.When he first entered, it might just be an attack equivalent to that of a Golden Core cultivator, but as he gradually went deeper inside, Lin Haoming felt more and more pressure, and the black light emitted by the black cloak that wrapped his body gradually began to dim down.
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Although the six towers in Fangshi are all connected, in fact, depending on their Gummies Jjfg Do Results Real Ed Work cultivation level, some towers are only open to high level monks.According to the information given to us by Master Wuxin, at first the six demon sects advocated that all the sites except Falun Mountain should be divided up by them, but the master argued hard, and finally They promised that if they need to occupy the territory, it s okay.
However, there are still some Tianyi heavy water to replenish, but it is not a small gain.He Shengmo said sadly after hearing Lin Haoming s words Master, she had already passed away accidentally when I was ordered to come to Tianmomen.
At this time, she didn t intend to answer, and she was thinking about how she would get out of here once Lin Haoming was finished.Above the surface of the sea, there are no islands within ten thousand miles, but this is not a problem for those who have already arrived here.
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Mo Xiang smiled and said Senior brother said that he has always wanted a younger sister all his life, but he has been traveling all his life and has no fixed place.
