DNS uses a hierarchical and distributed way of resolving names to IP addresses.
DNS使用分层和分布式的方式将名称解析为IP地址。
[ Silence ]>> DNS, Domain Name System, uses a hierarchical distributed wayof resolving names to IP addresses.
域名系统>> DNS采用分层分布式的方式将域名解析为IP地址。
What better way to understand the system than to go through an actual example?A client device wants to go to www.RIT.edu.
还有什么比通过一个实际的例子更好的方法来理解这个系统呢?
客户端设备需要访问www.RIT.edu。
In addition to an IP address, subnet mask, and default gateway IP address,the client's configuration will also have an IP address for the DHCP server and the DNS server.
除了IP地址、子网掩码和默认网关IP地址之外，客户机的配置还将具有DHCP服务器和DNS服务器的IP地址。
All FQDN's that need to be resolved to their corresponding addresses will startwith the client querying its DNS server.
所有需要解析到对应地址的FQDN都将从查询其DNS服务器的客户机开始。
Let's assume nothing is cached anywhere.
让我们假设任何地方都没有缓存。
By the end of our story, answers will be cached in multiple places.
在我们的故事结束时，答案将被缓存在多个地方。
This client device on some network and domain will query one of it's local DNS servers.
某些网络和域上的这个客户机设备将查询其中一个本地DNS服务器。
Typically, enterprises will have two DNS servers setup for both full tolerance and load balancing.
通常，企业将设置两个DNS服务器，用于完全容忍和负载平衡。
One will be the client's primary DNS server, and will be the first one it asks.
一个将是客户机的主DNS服务器，并且将是客户机请求的第一个DNS服务器。
In this case, the client asks its DNS server, "What is the IP address for the machine named"www" in the subdomain "RIT" in the top level domain "edu"?".
在这种情况下，客户端问它的DNS服务器，“在顶级域“edu”的子域“RIT”中名为“www”的机器的IP地址是什么?”
Again, assuming nothing is cached, the client's DNS server will not know the answerand escalates the query to one of the 13 root DNS servers.
同样，假设没有缓存任何内容，客户机的DNS服务器将不知道答案，并将查询升级到13个根DNS服务器之一。
There are actually hundreds of machines in many countriesaround the world acting together sharing 13 logical IP addresses.
实际上，在世界上许多国家，有数百台机器在一起工作，共享13个逻辑IP地址。
The root server selected will respond back to the clients DNS server with a referral.
所选的根服务器将使用引用对客户端DNS服务器作出响应。
Every top level domain, like .com, .net, .edu, is maintained by a registry.
每个顶级域名，比如。com。net。edu，都是由注册中心维护的。
The .edu authoritative DNS servers are responsiblefor knowing the authoritative DNS servers for each subdomain in "edu".
edu权威DNS服务器负责了解“edu”中每个子域的权威DNS服务器。
In other words, the "edu" authoritative DNS servers can't possibly be taskedwith knowing the IP addresses of every resource in RIT.
换句话说，“edu”权威DNS服务器不可能被要求知道RIT中每个资源的IP地址。
edu, as well as every "edu" subdomain.
以及每个“edu”子域。
Think of all the overhead that would be involved!
想想这将涉及到的所有开销!
Not only storing all that information, but maintaining it as well!
不仅要存储所有这些信息，还要维护它们!
When a resource is added, removed, or modified, the single authoritative DNS server for that"edu" TLV would have to be involved.
在添加、删除或修改资源时，必须涉及该“edu”TLV的单个权威DNS服务器。
Furthermore, RIT and other colleges wouldn't even want this,as many resources are internal and private.
此外，RIT和其他大学甚至不希望这样，因为许多资源是内部和私人的。
The only thing the "edu" authoritative DNS server needs to know is a point of contactat RIT.
“edu”权威DNS服务器需要知道的唯一一件事是RIT上的联系人。
edu, the authoritative name servers for the RIT.edu domain.
edu, RIT的权威名称服务器。
edu域。
So as far as our story goes, the client machine asks it's local DNS server, who puts the clienton hold, and asks one of the 13 root DNS servers.
到目前为止，客户机机器询问本地DNS服务器，是谁将客户机挂起，并询问13个根DNS服务器中的一个。
The root server queried gives a referral back to the client's DNS server for the IP addressof one of the authoritative DNS servers for the .edu top level domain.
查询到的根服务器将向客户机的DNS服务器提供对.edu顶级域的一个权威DNS服务器的IP地址的引用。
If the client had queried for the IP address in a different TLD, like .com,the referral would be for an authoritative .com TLD DNS server.
如果客户端在不同的TLD(如。com)中查询IP地址，则引用的是权威的。com TLD DNS服务器。
The .com authoritative DNS server needs to know the point of contact DNS serversfor subdomains in the .com top level domain.
权威DNS服务器需要知道顶级域的子域的联系人DNS服务器的位置。
In fact, the same is true for the authoritative DNS servers for every top level domain.
实际上，每个顶级域的权威DNS服务器也是如此。
They need to know the point of contacts for each of the subdomains in their top level domain.
他们需要知道顶级域中每个子域的接触点。
In our story, the authoritative DNS server for the .
edu domain gives a referralto the authoritative DNS servers for the RIT.edu domain.
在我们的示例中，.edu域的权威DNS服务器提供对RIT.edu域的权威DNS服务器的引用。
Now the client's DNS server finally has the IP addresses of the authoritative DNS serversof the RIT.edu domain, and asks one of them the same question, "What's the IP addressof the machine named "www" in the RIT subdomain of the .edu top level domain?".
现在，客户机的DNS服务器终于拥有了.edu域的权威DNS服务器的IP地址，并问其中一个相同的问题:“.edu顶级域的RIT子域中名为“www”的机器的IP地址是什么?”
One of the RIT authoritative DNS servers gives the answer back to client's DNS server.
其中一个RIT权威DNS服务器向客户机的DNS服务器返回答案。
It's 129, 21, 1, 40; and the client's DNS server gives that answer back to the clientas if it knew the answer all along.
129 21 1 40;客户端的DNS服务器会将这个答案返回给客户端，就好像它一直都知道答案一样。
At home, like our DHCP server, our DNS server exists in that little boxthat everyone simply calls router.
在家里，就像我们的DHCP服务器一样，我们的DNS服务器存在于每个人都称之为路由器的小盒子里。
Like the DHCP service in that box, the DNS service is not as robustas it is on an enterprise server.
就像那个盒子里的DHCP服务一样，DNS服务没有企业服务器上的那么健壮。
All our DNS server really does is send all queries to our ISP's DNS server.
我们的DNS服务器真正做的是将所有查询发送到ISP的DNS服务器。
Our ISP's DNS server then does the heavy lifting to get the answer,delivers it back to our DNS server, and that little box called router,who then gives the answer to our client device
ISP的DNS服务器会做一些繁重的工作来获取答案，然后将其发送回DNS服务器，然后路由器会将答案发送给我们的客户端设备
转载于:https://www.cnblogs.com/sec875/articles/10380970.html
