| For the Internet, people always talk, but few people are willing to learn computers, mobile phones, television in the end is how these devices are "connected" together. Through the "I", a common network requests perspective, to introduce under the "I" is how the workflow. |
People move a finger, little mouse, pictures, videos will naturally instantly displayed on the screen. But, all is not as it should be, under the colorful world of the Internet, we are working around the clock.
I am an ordinary network requests. I was very small, but always in fulfilling the responsibility - to find the specified resource, and then deliver them to my master hands. Like the city tens of thousands of unknown but express little brother, shuttling between the buildings and the buildings to complete the mission.
The difference is that real network environment is not like a modern city so glamorous. It is dark, damp, full of unknown dangers, like a dark forest. And I have to do, it is a fully-fledged adventure.
URL and IP in the end is what?
My adventure, from a "scrolls" Speaking. That day, the browser Uncle mysteriously call me over and told me that CPU issued a command : to send a messenger to access the Gentiles. And my uncle is the most effective disciple, is the most suitable candidate for this type of task. I've got an uncle for the scrolls, the above record the necessary information I need to use this adventure.
Doing my part, I took it, leave immediately.
I started slowly scrolls, was shocked to read the first line: URL: https://mail.google.com
What is "URL" I quickly recalled in the brain, on a URL that is the abbreviation of Uniform Resource Locator,?! translated into Chinese is "uniform resource locator." Because the Internet world there are countless resources, every resource we need to have a mark to locate it, just as the house number of human cities.
One might think that, as with house number, it will not be easy to find the appointed place? My friends, I hope so, but the reality is often not so simple.
Even with the URL, I am afraid I stupid, I still can not understand it points directly to destination. Because this is the language that I can not translate interpretation. (In fact, stupid humans, can not remember the IP address, you need to use easy to remember domain name instead)
For me, the IP address is the unique set of coordinates. What is IP? IP abbreviation for Internet Protocol, ie, the Chinese translated as "Internet protocol", a guys name, one of the cornerstones of the Internet, everything had to rely on the Internet for communication software follow this protocol.
So how do you convert domain names into IP address?
Browser uncle in his spare time on weekdays, very careful, he visited the site users have compiled a "list of domain names -IP correspondence." If an IP address has been recorded, then he will tell me that I can start immediately towards the destination IP address, which is the browser cache role.
If the URL is not within the scope of recording the browser of the user input, the operating system looks for a "hosts" file name. It is a text, record the mapping between domain names and IP addresses. If the "hosts" can tell me the destination IP address, that can save me a lot of effort. This is the system cache.
In addition, the router cache, I believe I do not have much describes, is saved in the router's domain name -IP map.
These caches can effectively help me with the fastest speed to find the corresponding IP address. However, the Internet world is changing, resources abound. In many cases, users will want to access a new, any cached had no record of the domain name.
To this end, mankind specially designed DNS. In this mission, my first stop is rushed to the DNS. For shorter response time and a better user experience, my full speed.
About DNS hijacking memories
What is DNS? Stands for Domain Name System, is a mutual mapping domain names and IP distributed database.
The world there are many DNS service center, if you care about your computer, you will find on your card, with a "DNS server" configuration items, which I will get to set the destination. 
What is DNS hijacking, poisoning, analytical? Look at this article, you understand!
A fraction of the effort, I came 114.114.114.114DNS center.
I came to this place many times, calm on the surface, but in reality simmering. I carefully went to work the hall, I can not help but think of the first time DNS hijacking experience.
That day, I went to work the window, the teller warmly received me.
"? Sir, do you want to address what the query" At that time I was a budding web request, inexperienced still shallow, do not know can not be said of some of the regulations, so forthrightly he replied: "Hello, I'm going to the famous the mail.google.com! "
teller's face suddenly froze, he looked me up and down, then hard and forced a smile," Yes, sir, please wait. "then, a colleague next to him Bianxiang winking. I was wondering what, suddenly sprang on both sides of burly guards strapped me to a drag force.
I realized something was very wrong, "how is this going?! Why you hijacking me?" I made Fengliaoyiban screaming.
"Hello, according to the regulations of the ISP (telecom operators) promulgated by the world does not exist on the site you mentioned, is now suspect you are a non-compliant network requests, you will be forwarded to the IP address of baidu.com. you have the right to remain silent! "the guard looked at me coldly.
I know that now anyway explanation, struggling to no avail, and can only blame themselves too young. Helpless, I had obediently into submission. 
What is DNS hijacking, poisoning, analytical? Look at this article, you understand!
Fortunately, when the user is using some of the computer network knowledge, when he found himself input is google, baidu page is returned, there is no blame on me, his mind probably already guessed the reason. So he will DNS network card is configured to: 8.8.8.8, which is on an international "does not exist," the company provides DNS service center.
This will only unimpeded access to the Internet yet? DNS hijacking is gone, I still can not relax.
I have met DNS poisoning
还未休息片刻，浏览器大叔再一次地给我分配了任务：继续尝试请求mail.google.com的资源。
人类出国要坐飞机，要办护照。我们网络请求也是这样，全国只有在几个主要城市才会部署国际出口，所有访问境外资源的网络请求，都得经过这儿接受检查。
与上次不同，因为这次我要访问的DNS服务器位于海外，所以我首先来到了大中华局域网的上海国际出口。
我一路奔波到上海真的是又累又乏，正当我火急火燎地准备过安检，通道附近有一位穿着制服的小伙迎了上来。
还没等我开口，他热情地迎了上来：“远道而来的朋友，一定是十分疲惫了吧?天气这么热，先喝杯水吧!”我悄悄地打量着他，看他的打扮应该是一位服务人员。
“国际出口就是不一样啊，服务真到位!”由于确实是太渴了，我放松了警惕。“啊，真清凉，谢……”我一边感叹着，一边接过了小伙递给我的水。
可当我第二个“谢”字还没说出口，立即感到一阵头晕目眩。
“不好!遇上了黑客，这是DNS投毒!”我的视线渐渐模糊，小伙的微笑也渐渐似乎变成了狞笑。我尽力搜索着脑海中和这一切有关的知识，想要知道寻求的办法。
什么是 DNS 劫持、投毒、解析？看这文就懂了！
DNS投毒，英文叫DNS cache poisoning，也叫做DNS污染。从客户端向DNS服务器发出查询IP的请求，到响应返回到客户端的这段时间里，如果有黑客或者其他一些不可说的设施伪造返回了一个错误的DNS应答，那么用户将不能访问到真正的资源。
想到这里，我已经明显感觉难以控制自己的身体了，眼前一黑，就什么都不知道了。
DNS正常解析
Dangerous situation happened before vividly, and now think of it, I still have a lingering fear. This time, for sure, I'm playing the spirit of twelve.
This time, I have successfully come to 8.8.8.8 DNS Service Center.
"Hello pro, what can help your thing" in the service window came the sound of soft sister.
"I am asking for the IP address of the domain name mail.google.com." I tentatively asked, still can not relax.
"Yes it pro, here by the tree search at a top-level domain com, google query to the directory inquiry into the mail in the google directory, IP address is xx.xxx.xx.xx it." 
What is DNS hijacking, poisoning, analytical? Look at this article, you understand!
I was relieved, thank goodness, finally got the results. I know as a complete network request, which has just begun, this is the first step in the long march, I've got to resolve this result to take home, and so will have non-stop round trip three times to establish a connection.