Domain Name Server (DNS) is the Internet important, but unseen part, and forms one of the largest databases. Each computer on the Internet is given a unique address, called IP addresses, which is 32-bit number, and four bytes. The way users said that the IP address in dotted decimal notation, "in the world. A typical address looks like this: 199.249.150.4
It is difficult to remember all our sites daily visits, because it is not easy to remember the number of strings of IP addresses. However, we forgot the words. This is the domain name in the picture. If you want to connect to a Web site, you need to know its IP address, but wanted to know its URL. Acquired the domain IP address mapping and the corresponding name.
Name and Number
Translates domain names (such as www.xyz.com) the name of the machine resolves the IP address (eg 199.249.150.9). Basically, converting it from an address to a name and address and name.
From the mapping of the IP address of the computer name is called reverse mapping. When you enter your http://www.xyz.com browser type, the browser first need to get the IP address of www.xyz.com. The machine uses a directory service to find the IP address, the service is known as domain names. When you type www.xyz.com your first contact with the machine, DNS server, asking it to find the IP address of www.xyz.com. This DNS server can get nakakaugnay by Taiwan with other Internet DNS servers. DNS is therefore considered a global network of servers. The big advantage of DNS update any organization. This is called a distributed database known.
The three-letter code
DNS server is a computer running DNS software. The most popular of the DNS software that Bind's (Berkeley Internet Name Domain) DNS is a hierarchical system tree. Above is a gift. '. Is known as the root system. There are seven root following a direct sub-domain nodes, and these are 'the government website COM', 'Oxford','', 'mil', 'net', 'edu', 'clean', etc.
Domain consists of two parts
* Name Server
* Decomposition
Domain Name Server:
It is found in search for the name of the activity. Usually, a cluster of machines for the domain name servers. If the domain name server does not contain the required information will be linked to another server name. However, each server needs to know how to contact all other servers.Each domain name server will know how to contact the root name server, which in turn also know that every two domain names in all of the power of location servers.
Decomposition:
This runs counter to start the DNS check on the client computer. It contains a list of domains that use the name servers. As we read, for each of the domain name server function is to resolve the question name. There are three types of domain name servers, domain servers, primary, secondary domain name servers and Caching name servers. Secondary domain name server is configured for backup purposes. Caching name server to resolve the question of the name only, but do not have any DNS database files. It is important to point here that the primary domain name server, any change must be propagated to the second server. This is because their primary domain name server records in the database. These changes through the dissemination of 'zone transfer'.
How to "Cache" Industry
DNS using the 'principle of cache' operations. When the domain name server receives a message mapping, it caches this information. Additional questions, the same mapping will use the cached result, thereby reducing search costs. The domain name server is not cached.Cache is a component called time to live (TTL) and the TTL determines whether a server will cache a message. Therefore, when the Caching name server receives an IP address, it receives its TTL. The domain name server cache the IP address of a time and then discard it.
When the process needs to identify an IP address in the address of the DNS, called for a solution of address, the local host. It is possible in different ways:
Table lookup. In the UNIX host, table / etc / hosts.
With the local domain name server mode of communication. This is called the UNIX system.
By sending a massage to the remote system, the information from the file specified by / etc / resolve.conf.
When the domain name server receives a domain is not as questions, may be sent back to the client references a given domain name server for the better. Often work in a recursive way any DNS server is requested it can handle a higher level, server, etc., until the necessary, or until you can handle the root DNS name of the place so far.
The domain name server contains links to help other domain name servers, it can traverse the entire domain naming hierarchy. The original address in the domain name server host must also be configured. Then, it can use DNS to find domain name server protocol or a DNS naming hierarchy is responsible for.
So, when a domain name server receives a request, it can be one of the following:
It answers a request to IP address. This method is called iterative. Consideration, the customer has to ask the server to resolve domain names. Server to access the database and found that his IP address and send back. If the server does not find the address, it sends back an error;'s DNS not found '). Contact other nameserver and try to find the name of the requested IP address. Sent back to customers and better referral to a designated IP address of the server domain name.
A popular user interface, called 'nslookup'is UNIX system. With it, you can perform any DNS function. The plan also shows results for the user. Nslookup to use, you can get a zone list of all hosts. To do this, you first to determine the server of the domain name in the region.
The DNS is used for the integrity and authenticity of DNS data from the inspection to the lack of related threats. In addition, other protocols can use the access control mechanism for the host name. Internet Engineering Task Force (IETF) has DNS Security (DNSSEC's) DNS extend the agreement. The main goal of DNSSEC is to provide authentication and integrity of the DNS. The above requirements by encrypting using '
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