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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The person who died back then seemed to be reborn in another way.Although Yin Fengling told her some things, but looking at Han Ningxiang s harmless little face, and adding that her life was indeed saved by her, it didn t do her any favors.
Because the Shuangfeng River divided Jinhu County into two parts, there were also Beifangshi and Nanfangshi.Seeing the figures of the two working hard, Han Ningxiang had a strange smile on her lips, and then walked to the tight wooden door of the hut.
After Lin Haoming and Han Ningxiang selected a room, they immediately closed the door and warned the servants and maids in charge of this room not to disturb them without their permission.Compared with the other two Xuan generals, Rong Ke was the last to arrive, and the people he brought also made the two who arrived one step earlier, and Cui Fei, show some interesting expressions.
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At the beginning of arresting people, Lin Haoming held the idea that he would rather catch the wrong than let them go, so at least one tenth of the officials above the seventh rank and above in the entire Land Thieves City were captured, and there were more than 20 palm printed heavenly officials.
When the light slashed, the giant ape immediately slashed in half.Sometimes people like Yao Dong also live here, and now Wu Li lives there temporarily.
Don t worry, my lord, I will definitely find out everything Di Zhong could only promise at this time.At this time, Lin Haoming also asked Shu Siyue and the others if they wanted to go around the West Market, but in the end, everyone decided to have a meal here and enjoy the night view before leaving.
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This kind of thing is still unknown. Now that I heard it, I remembered that in order to frame Suni, I used her as my own.After all, the latter two items, whether it was the Earth Yang Fruit or the Cold Essence Crystal, were not something that a cultivator in the Mystic Profound Realm urgently needed, unless that person himself was a cultivator of ice and fire.
This is a letter from Mrs. Shu, and Mr. Shu proposed to recruit us. Yin Fengling said, and put the letter Just took it out.The two also exchanged items. After Lin Haoming got the items, he immediately put them away, and then walked to the seat and sat down.
The condition is very simple. I don t need your accumulation over the years.The big auction is over, but it does not mean that the trade fair held in Devil Slaughter Castle is over.
Instead, there were two tall and mighty warriors standing at the door, but the kind of wandering people would be discouraged at the first glance.Once here, Lin Haoming immediately smelled a faint fragrance of medicine, and his spirit was shocked.
After all, they only went to the thief city once, and they completely surrendered to Lin Haoming.In addition, the more important discovery is that there are several stones that have never been moved.
Back at their place, Lu Yao and Shi Qing had already made tea for themselves and packed their things neatly.Shu so smoothly, and thus became Mr. Lin s assistant.
When building this fort, many monks with great supernatural Finding the Best High Potency CBD Gummies for Enhanced Wellness powers worked together to cut off a section of the mountain before it was built.Cui Changting Of course he is dead Lin Haoming replied disdainfully.
In fact, Lin Haoming also knows that the people in his hands are full of conflicts with each other, but if he wants to seize the time to do it, he must act first, otherwise, once the people of the Tongtian Gang change everything that Bai Laosan revealed, at that time they will attack Finding the Best Children's Sleep Gummies Without Melatonin: A Comprehensive Guide the third man.
Lin Haoming just smiled slightly, waved them to go out, looked at Guan Liang and Pan Zhen, and Zhu Youming who also walked in soon, and asked Master Guan came to me in a hurry, what s the matter What is it, Mr.Even if he gave up, it is naturally impossible for anyone to fight for it.
Feeling the coldness coming from her face, the woman immediately didn t dare to speak again.
What s the compensation Bailifeng and I entered the virtual world together, and we are considered fellow villagers.According to Bai Laosan s confession, the reefs in this reef formation are divided into bright reefs and hidden reefs.
Come out, isn t this elixir given to me by the woman just now I really think I am a fool, I can t even tell this point, since it is definitely not poison, don t blame me The woman took the bowl from Han Ningxiang, saw that the medicine inside had indeed melted, so she immediately drank it all, and after a while, she seemed to feel much better, and then she put on her clothes.
After thinking about it, I think it s still the magic energy and the magic energy.Both the pill formation rate and the pill yield rate were higher than expected, which made Lin Haoming quite uncomfortable.
As the better time came, Lin Haoming also went to the house again, and discussed with the owner of the house about buying the house.Yinye sighed, especially when she finally found out that Lin Haoming had sneaked into the Third Ring State by himself.
On the following day, following the news of Jiang Tianqing, almost the entire top of the thief city knew that the long vacant Zuo Tongzhi had arrived in just one day.Sure enough Seeing the magic clock working, Lin Haoming was determined, and snapped his fingers at the big clock.
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This is a gorgeous dividing line It s a gimmick, but I didn t expect that the other party chose that kind of stone.The two kept chatting, and Lin Xuan mostly asked about the palace.
Boom boom boom, a lot of sword energy around Qixing was swept away.However, at this time, Lin Xuan spoke again, be careful, there is a formation here, and you can only choose one of the treasure boxes.
This is still the strength of the three of Lin Xuan please remind netizens Please pay attention to rest your eyes when reading for a long time.Did you hear that kid, a little casual cultivator dares to provoke me Go to hell with me He raised his palm, surrounded by the aura of chaos, and then slapped it out.
When the thunder cloud disappeared, King Li s figure also manifested.That is to say, the opponent has quasi powerful strength.
This is a gorgeous dividing line One, it s definitely big.Those strong men from outside were even more surprised.
Those elders of the royal family were all stunned. They looked at Lin Xuan s figure, and couldn t believe how damn it was possible.Afterwards, Taoist Long said, we have been fighting and chasing and killing these days, and I am afraid that we have consumed a lot.
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In the end, a crack was torn. That s great. Lin Xuan was overjoyed and speeded up. And the people around were shocked when they saw this scene.I belong to Lan Haifeng, and she belongs to Hei Yufeng.
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At this moment, he is like a sword god, terrifying.Lin, what should we do, Qiankun Sword King and others asked.
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There are many dangers in this place. After saying this, Taoist Long snorted coldly, and a red armor appeared on his body, and it continued to expand.On the other side, King Duan Yun also used the King s Domain, forming a huge palm, rushing forward overwhelmingly.
Others also displayed their unique skills one after another, resisted with all their strength, and quickly withdrew.According to the legend, this is not an Earth level exercise, but a Heaven level exercise.
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Lin Haoming wondered. My lord is really sincerely asking for safety Lan Qingyu asked again.If the strength is damaged, most of them will choose to escape quickly.
Don t worry, my lord, this subordinate will never dare to live up to your expectations this time Jin Ren promised quickly.Mrs. Yinye, you are a little too naive. I put a mark on your daughter. It is impossible to steal a dragon and turn a phoenix, and you think that even if she is really Can I live if I leave Lin Haoming said coldly.
In fact, at this time, even if he doesn t do anything, Lin Haoming believes that this senior Murong Introduction will not let him go.Jia Qiniang seemed to be aware of her physical condition at this moment, seeing Lin Haoming s anxious look, she smiled for a moment.
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If I don t use all my strength, I m afraid I will be in danger instead.although some reefs were cleared, resulting in a big gap in the reef array of the Three Rings, but as long as the gap is guarded, other places don t need to worry too much.
Based on her understanding of Gu art, Shu Siyue naturally couldn t see any problems, but on the contrary, she did it on purpose.Although you are close to death, there is still a chance of life, but I must guarantee it Chang Yuan also seriously demanded.
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After Lin Haoming got it, he glanced at it. It was indeed Han Ningxiang s name written on it, and he couldn t see anything wrong with it, so he clasped his hands together, and the deed of prostitution was completely transformed into a fly in Lin Haoming s hands.The person who spoke was naturally Lin Haoming, and he did have his own intentions when he said that.
Yes
yes, I didn t know she was a senior, and I will never appear again in the future, but today I am not alone I came here, Finding the Best Gummies for Sleep and Pain: A Comprehensive Guide and I did come because of my son s injury Although He Yingsheng was afraid, he still said these words.Seeing the surprised expression on her little face, Jia Qiniang pinched her cheek with a smile, and said softly Your father has supernatural powers, such a treasure that can withstand the blows of the Profound Realm, how important it is to him.
The Cold Essence Crystal the size of broad beans, the Diyang Fruit, and the Sky Void Pill, these three things should be enough to exchange for the three materials.Although Zhou Mengli s mother is the daughter of the Wu family, she has always regarded herself as the Zhou family, even more determined than the average Zhou family, but due to her status, she has been relatively silent since the Zhou family was about to defect.
During this period, some runes could be seen shining, obviously there was a kind of brilliant magic circle covering it.It was Fang Buque who attended the meeting instead of Qi Tianlong.
He thought about it, and he had to make up for it as much as possible, so he said City Finding the Best Probiotic Gummies for Adults: A Comprehensive Guide to Supporting Digestive Health Master Lin, you can find someone, I ll go with you At that time, Huang Tiandu also let go of the palace master s airs, no matter what, he must control the matter.But even so, you are too risky Suni was still worried.
Although the woman called Sister Qingyu was surprised by the little girl s actions, she was shocked when she heard Fengling s name, and she was naturally much more sophisticated than Yinfengling, so she immediately put on a smile and said, Sister, scare you I m dead, I won t join in the fun anymore, my sister has no strength, help me in Lan Qingyu didn t just say this casually, she was Finding the Best CBD Sleep Gummies Reddit: A Comprehensive Guide to Improving Sleep Quality shot in the back, although she was in the water since she was a child Growing up, he was very good at water, he controlled the bleeding in the water to prevent others from catching up with him according to the bloodstains, but injuries are injuries, at this moment, it was the limit to be able to climb out of the water in time, but his body was exhausted.
It can allow soldiers below the Shenxuan Realm to fly into the sky to fight.You kept saying you were wronged, so explain why the other party let you out with a little precaution Rong Ke asked.
The more people from the other side, the better. As long as the remaining black flame bombs are enough to destroy the two nearby rocks, one and one, and two nearby rocks, that s all.With the chirping sound, Lei Peng s whole body suddenly swelled up.
At this moment, he felt more and more that the incident in front of him had a lot to do with his previous attack.At the same time, he kept spraying black mist towards Lei Peng.
After rising to a height of Zhang Xu, the rays of light covering the coffin lid quickly condensed into one ball, and then fell towards the inside of the sarcophagus.At first she was a little worried, but compared to the East Market, the West Market is much more Introduction lively.
As the boat entered the Fengling River, Lin Haoming also smiled and said Captain, the guards are quite polite, unlike what I have seen in other places After hearing this, the captain surnamed Tian smiled wryly and said Guest officer, when Unveiling the Best Male Gummies for Enhanced Libido and Performance we live on the river, these monsters, ghosts, and snakes must be worshipped.
Lin Haoming nodded, and then discussed some details, and then the two left without staying.At this moment, he only wants to ask Lin Haoming to pay the price.
Don t talk yet, I ll take a look at your injuries Han Ningxiang said.At the same time, the golden armored beast , the golden light on his back kept flashing, and long thorns flew towards him, as if he would not stop until he nailed Lin Haoming to death.
Li De replied, and took out the jade slip with the request for help after speaking.
