Root name server - Wikipedia
If you're online a lot, you use domain name servers hundreds of times a day -- and Thanks to DNS, though, you don't have to keep your own address book of IP connection includes resolving the domain name "badz.info" into an IP HowStuffWorks, a division of InfoSpace Holdings LLC, a System1 Company. 4 Structure of DNS; 5 Clients wants IP of badz.info; 6 Root DNS Servers; 7 Top . The root DNS servers (root name servers) keep track of all the authoritative . Many companies and usually all ISP use DHCP (DHCP is covered in section in. The authoritative name servers that serve the DNS root zone, commonly known They are configured in the DNS root zone as 13 named authorities, as follows. which is comprised of the organisations that manage root servers, maintains a.
Top-level domain names, also called first-level domain names, include. Within every top-level domain there is a huge list of second-level domains. For example, in the. COM first-level domain there is: COM top-level domain must be unique. The left-most word, like www, is the host name. It specifies the name of a specific machine with a specific IP address in a domain. A given domain can, potentially, contain millions of host names as long as they are all unique within that domain.
IANA — Root Servers
DNS servers accept requests from programs and other name servers to convert domain names into IP addresses. When a request comes in, the DNS server can do one of four things with it: It can answer the request with an IP address because it already knows the IP address for the requested domain.
It may have to do this multiple times. Your DNS server would ask the root for www. Your name server then contacts the DNS server for http: It actually does, so it returns the IP address to your DNS server, which returns it to the browser, which can then contact the server for http: One of the keys to making this work is redundancy.
There are multiple DNS servers at every level, so that if one fails, there are others to handle the requests. The other key is caching. Once it has made a request to a root DNS server for any. DNS servers can do this for every request, and this caching helps to keep things from bogging down. Even though it is totally invisible, DNS servers handle billions of requests every day and they are essential to the Internet's smooth functioning.
The fact that this distributed database works so well and so invisibly day in and day out is a testimony to the design. Clients and Servers Internet servers make the Internet possible. All of the machines on the Internet are either servers or clients. The machines that provide services to other machines are servers. And the machines that are used to connect to those services are clients.
There are Web servers, e-mail servers, FTP servers and so on serving the needs of Internet users all over the world. When you connect to http: You are accessing the HowStuffWorks Web server. The server machine finds the page you requested and sends it to you.
- How Domain Name Servers Work
- Communication Networks/DNS
- Root Servers
Clients that come to a server machine do so with a specific intent, so clients direct their requests to a specific software server running on the server machine. For example, if you are running a Web browser on your machine, it will want to talk to the Web server on the server machine, not the e-mail server. A server has a static IP address that does not change very often. A home machine that is dialing up through a modem, on the other hand, typically has an IP address assigned by the ISP every time you dial in.
That IP address is unique for your session -- it may be different the next time you dial in. This way, an ISP only needs one IP address for each modem it supports, rather than one for each customer. Ports Any server machine makes its services available using numbered ports -- one for each service that is available on the server.
For example, if a server machine is running a Web server and a file transfer protocol FTP server, the Web server would typically be available on port 80, and the FTP server would be available on port Clients connect to a service at a specific IP address and on a specific port number.
In delegation, the parent zone contains NS records that specify the names of DNS servers in the child domains along with A glue records that contain their IP addresses.
Root name server
The wizard walks you through selecting the child domain name and identifying name servers in the child domain. If someone takes down a child DNS server for maintenance, or decommissions it entirely, without notifying the DNS administrator in the parent domain, the delegation records in the parent zone become invalid. This is called lame delegation. You can also get lame delegations by blocking zone transfers to a secondary server if the secondary server has an NS record in the parent zone.
This sometimes happens during an overzealous security sweep. Lame delegations can also cause connection failures when desktops in one domain try to connect to servers in other domains, although this might not be obvious right away if you use WINS.
If you deploy Windows DNS servers, you can avoid lame delegations by using stub zones. The parent DNS server periodically refreshes the stub zone contents, drastically reducing the chance of having a lame delegation. You can download DNSLint from download. DNSLint is a command-line utility that does two sets of tests: Figure 5 shows an example. This essentially makes your internal DNS server a slave of its forwarders; so specify two or more forwarders and try to use servers in different subnets, if possible.
DNS Server properties showing the option to avoid using recursion when forwarding. If you allow your primary public DNS server to accept recursive queries and cache the results, you open yourself up for cache pollution. It finds the name server for deviousdomain. In return, it gets the host record but it also gets a flock of name server NS records for domains such as Microsoft.
You should also enable cache pollution filtering in the DNS server Advanced properties. Do this for any server that accepts recursive queries, internally or externally.
Some of the restrictions apply only to the gTLD server operators, but the suggestions and requirements for maintaining a secure, safe DNS platform are worth your consideration. Also, take a trip to www.
Any machine can assert itself as an existing host and overwrite the A record with a new IP address. This essentially allows a machine to hijack the DNS records of another machine. If you want to use dynamic updates for a zone, integrate the zone into AD and permit secure updates only. This requires a client to use Kerberos to validate its identity, then initiate a secure transaction to obtain a signing key that it can use to digitally sign the update request.
Other DNS servers support secure dynamic updates, but not using this method. These servers use a form of DNS security that requires a shared secret key. If you do this as a habit, the test becomes a reflex. Take a couple of precautions to keep from getting fooled by caching. You can get interesting problems if you remove a member server from service but forget to remove the corresponding A and PTR entries from DNS.
This can be difficult to troubleshoot if you reference multiple servers with the same host name. Windows DNS uses round robin load sharing; so if you take a server down for maintenance and forget to remove the A record from DNS, not every client gets an invalid A record. Windows DNS also uses round robin for cached entries, so flush the cache if you take a DNS server down for maintenance.
The server still has DNS running, but has no local zones so it starts acting as a caching-only server. Depending on the forwarding configuration and NS records stored in the local Registry, it might even appear to work normally, which is unfortunate. It would be better if it failed completely so you could fix it right away. Clients can also get invalid information if you set up a public-facing DNS server behind a NAT firewall and the server has glue records that reference private IP addresses.
You should avoid publishing private addresses entirely or get an application layer gateway capable of translating glue records. Queries for each label return more specific name servers until a name server returns the answer of the original query.badz.info
In practice, most of this information does not change very often over a period of hours and therefore it is cached by intermediate name servers or by a name cache built into the user's application. DNS lookups to the root name servers may therefore be relatively infrequent.
Some misconfigured desktop computers even tried to update the root server records for the TLDs. A similar list of observed problems and recommended fixes has been published in RFC Although any local implementation of DNS can implement its own private root name servers, the term "root name server" is generally used to describe the thirteen well-known root name servers that implement the root name space domain for the Internet's official global implementation of the Domain Name System.
Root server addresses[ edit ] There are 13 logical root name servers specified, with logical names in the form letter.