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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Hearing Qingyang s analysis, Guo Kaifeng s eyes lit up and said, Yes, if we hadn t found the key point and poked the opponent s sore spot, how could he have sent so many blood bats to stop us So the opponent really is Are you exhausted Not only that, but the fact that the other party is so strongly preventing us from destroying the stone gate, doesn t it mean that there are some big secrets behind the stone gate, or even rare treasures
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This spirit stone was obviously not buried artificially, which means that it is very likely that this is a spirit stone vein, and it is a spirit stone of high quality.Suddenly, there was a trance in front of the eyes, and Qingyang, Jiao Hong, and Xiqiu all escaped from the illusion.
More than 800 people almost filled the square in front of the city lord s palace.He knows the situation here very well. He introduced it while walking, giving everyone a general understanding of the entire Jingfeng Mountain.
It is a low grade spiritual weapon like Liang Yudong s Butter Umbrella.Absolutely impossible Qingyang said firmly without any hesitation.
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We are just a small business. We can t make one or two hundred spirit stones a year, and we have to share it with many brothers below.At the end, the Demon Suppressing Hall caught a fourth level monster from nowhere and killed the sacrifice flag in front of everyone.
He looked like a monster at first, but now he looks like How Long Does 116 A Cannabis Gummy Last A Comprehensive Guide Nczth a real person.As long as he smashed the jade talisman with force, the escape talisman would take effect instantly, randomly teleporting him thousands of feet away.
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Returning to Qingfeng Hall, Qingyang first went to the outer hall to file a report with Master Deng.After all, what advantage did the human monks have It would be nice not to lose, but even if you win in the end, you will have to pay a heavy price.
Putting aside whether the Yin Yang Sect disciple could escape the pursuit of the living dead, Wei Yufeng was almost frightened to death when he saw that his junior fellow Bio 8226 Heal Blood Cbd Gummies Review A Comprehensive Analysis Of Effectiveness And Benefits Sokjv apprentice abandoned him and ran away alone.While Qingyang was thinking about countermeasures, he asked, What do you want to do Qiao Shan smiled and said, Why do you ask, fellow Taoist Qingyang, knowingly We just shared more than a hundred spiritual stones with you, and we feel a little sad.
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The price offered by Qingping San cultivators is not bad.
The epic material Deer Emperor s Heart obtained last time may be used directly if Turing is not available.But this is the method used by the aborigines, and the aboriginal forces will not use that kind of weak minded plan.
It is equivalent to investing in the territory and sharing the profits of the territory with the players.Boom The other party threw the black bear, which weighed several tons on its shoulders and was comparable to an elephant, to the ground and walked over slowly.
The sea of undead could not stop these strong men at all, and was torn apart by it, allowing teams to rush towards the pyramid.No more After hearing that the territory had a spell consultant who was good at alchemy, Nico instantly lost his doubts.
Because the biggest weakness of the aircraft carrier flow is the aircraft carrier itself.A mature explosive flying dragon appeared in front of Zhao Hao.
The information came through the Myth Guild channel.Not only will you lose profits, but you may also be liquidated.
Of course, even so, Zhao Hao was not careless. With Freya and Feida standing beside him, he would take action as soon as possible when an enemy attacked.The resources consumed are various types of gems, magic crystals, spell materials, magic plants
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Ellie and the others stayed behind to protect the convoy.Wow The sea water was smashed by the high speed Storm, and the speed of the ship continued to surge.
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In this case, he hopes that the pirates will come again.The reason for my enthusiastic attitude towards him is for two reasons.
The other party might be waiting for him to fall into a trap.According to Qin Hu s memory, that day he and his fianc e entered the palace to pay homage to the current Princess Chang an.
If there are more demons constantly attacking the transport convoy, it will be difficult to withstand it.Moreover, these forces will Say Goodbye 52 To Prostate Woes How Cbd Gummies For Prostate Can Improve Mens Health Hoxmj take care of themselves as natural and man made disasters occur again and again, and the refugees who will appear will be the real fat ones.
But Zhao Hao didn t know that on the branch not far from where he left, a crow with a somewhat stiff movement looked at everything in its jewel like pupils.With the Green Field Army blocking the forest, there is no need to worry about scattered monsters destroying wheat fields and buildings.
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Involving several chambers of commerce also meant that they would play a supervisory role.But where have I seen this look. Well, in reality, stray dogs are very similar to what they look like now.
It is precisely because of Curry s blessing that the Storm is not slow in flying in the sky and can arrive quickly.Obviously, the opponent was shocked by this series of amazing results.
Blackrock Wilds It is also where the largest number of half elf settlements are located.Now it seems that achieving this tactical goal is no longer a problem.
According to Qin Hu s memory in his previous life, about two hundred people were stationed here.
Instead, the Liu family was divided into two parts.Unless a formation master happened to pass by, it would be almost impossible to discover the temporary cave protected by the hidden formation.
Zuo Laozu saw the sincerity of what Li Shiming said.After Li Shiming arrived before the great monks of Taichu Sect, he gave up the best opportunity and did not take action immediately.
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Then more ice crystal bullets hit the sea beast s body continuously.After he activated six pairs of puppet statues in succession, the earliest pair of puppet statues also completely lost their ability to move after consuming the tenth flying sword.
This time he used twenty brains, and fortunately he had five Nascent Souls in his body, and all of them had practiced the Heavenly Art.After the selfless training of the sword ancestor, his sword s intention has long been different from what it used to be.
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The medium grade magic weapon Gatling in the hands of the bronze corpse sprayed out ice crystal bullets, which first dispersed the black mist.Although Xiaoleiyin Temple s own inheritance is nothing, it still left some treasures.
The five middle stage golden corpses of the great monk Luo Pei are still with the clone Li Yuanba.The great monk Luo Pei took back the spiritual treasure Black Water Sword , and his spiritual consciousness wrapped up the entire treasure pavilion.
In fact, this was not a trap against Li Yuanba at all.The knowledge he obtained from various places showed that the great powers were extremely dependent on the cave heaven and could not stay away from the cave heaven for a long time.
Finally, the last thunderbolt fell, and the whole world turned into white.When he discovered it, he was slowly absorbing spiritual energy to repair the cracks.
The energy in his body was completely unable to resist the attack of Ling Baoxing s sword.They all know how powerful Li Yuanba s mid term golden corpse is.
But even if the peripheral Nascent Soul mid stage monks knew about it, they could only obey the decisions of these core monks.It was a preparation to guard against the invasion of powerful men of the same level.
As long as he follows him, he will not have any worries.At the upper part, these vines spread out, waving one by one, like the long hair on a woman s head blown by the wind, or like the wickers flying in the sky in the strong wind, constantly releasing the sound of breaking through the air.
you didn t expect that I would break through the Nascent Soul realm at a critical moment, right There is a lot in this sentence, the most important one is that the old headmaster of the Blood Demon Sect, Master Lingxue, is actually dead This news not only shocked Elder Wusi and others, but also the monks of the Blood Demon Sect were surprised, because no news had been revealed before, and even the Golden Core monks didn t know about it.
Seeing that more than a dozen people were forced back, the Happy Ghost King smiled and said Hahahaha, you know how powerful I am, right I have said it before, even if my master is not here, you still can t run away.When fighting, the hair stands up like steel needles.
During that time, he also met many people in the Fallen Ghost Abyss, but after all, he did not belong here.Among them were Cheng en Mingzun and Chengci Mingzun brought by Baimei Ghost King.
It is of course better to prepare more. As for Wulongtan, since everyone knows about it , it is impossible to exclude others.In desperation, Qingyang had no choice but to try it himself.
Xi Ling er s appearance cannot be compared to Yu Mengmiao s Not much worse, the young man was a lustful ghost.The plants and trees seemed to be really made of gold and iron.
Could it be that everyone spent so much energy and paid such a high price to finally get to The Best Gummies To Sleep A Comprehensive Guide To Restful 12235 Nights Srjni this Goddess of Pregnancy Orchard, but in the end it was all in vain Thinking of this, many people became uneasy.Qingyang knew that the reason why the other party said this was because he was recognized for his strength.
Of course Fuliu Ghost King would not be captured without Proper Cbd Gummies The Proper 272 Way To Wellness hesitation, but the One horned Ghost King s method just now was too sudden, and he was caught unprepared for a moment.The Hundred Ghost Map also had restrictions. He could not be allowed to stop and rest halfway.
Seeing the pursuers coming from behind, Duanmu Fei s expression changed and she said, No, the men in blood are catching up with me.Qingyang really just felt this when he saw Hun Su like this.
He paused for a moment and continued Golden elixir monks who clear the Hundred Ghosts Map What Are Cbd 760 Gummies Used For A Comprehensive Guide can seek a position in the City Lord s Mansion.Those Nascent Soul cultivators in Chujiang City are all friends with you.
Everyone else had gone to the Dragon s Cave. Qingyang resisted the desire to follow and Wana Cbdthc Gummies Review A Comprehensive Guide To A 62461 Relaxing Experience Afzqg take a look, and continued to meditate in the Drunken Immortal Gourd.If Qingyang only killed twenty or thirty ghosts, some people might still be dissatisfied and kill fifty or sixty at a time.
In the past ten days, everyone still The 82559 Soothing Sip How To Make Marijuana Tea found nothing.As for the others, there may be newly promoted Nascent Soul monks, but these newcomers do not pose a threat to Qingyang.
Previously, Zhao Fu obtained the two powers of yin and yang by obtaining the power of the sun inheritance and the moon inheritance.What we did in this matter was not authentic. Now that we have lost the group competition, since God s will is like this, I think we Can You Get Addicted 0303 To Cbd Gummies Separating Fact From Fiction should forget it.
Although their strength has been improved, the danger has been greatly reduced.it was impossible to stay in the Fallen Ghost Abyss, so the Infinite Saint turned his thoughts to Shangguan Yan.
regarded this place as his home base. It is difficult to judge whether there are human monks inside, but the danger is certain.Unless they are lost, no low level monk dares to go deep alone.
The head of the Tian family knew that a poor place like Tianjiazhuang couldn t keep Qingyang, so he didn t say much.Then Elder Wusi took out a storage talisman from his arms and handed it to Qingyang.
He said angrily You
don t bully others too much. It was my fault for deceiving Mei Qing s niece.If the Golden Core monks clear the Hundred Ghosts Map, they can not only meet the Baimei Ghost King, but also get it from the city lord s palace.
It was probably the first time for the Underworld Winged Snake to meet a foreign monk.He suddenly regretted it. If the legendary Baimei Ghost King was like this, wouldn t he be Hua Mingshi looking for sin Finding The Best Cbd Gummies In Columbus Ga A Comprehensive Guide To Benefits Reviews 33 And More Gngpv preventing collection Automatic loading failed, click mode, please install the latest version of the browser nikdividdiv Speaking of how he cleared the Hundred Ghost Map with the ninth level of Jindan cultivation, it was more difficult than the original One Horned Ghost King, because the One Horned Ghost King passed the level to In the end, most of the people he met were ghost cultivators in the late Nascent Soul stage.
