Forex , Computer & Web Hosting

The name server (DNS) are an important but invisible part of the Internet, and one of the largest databases on it. Each machine on an internet is assigned a unique address called an IP address, which is 32 bit number and is expressed as 4 octets. The method used to represent these IP addresses is also called decimal notation.A typical address looks like this: 199.249.150.4

It is very difficult to meet the IP addresses of all the sites you visit every day because it is hard to remember sequences of numbers. However, remember the words.That's where they come from the domain name in the box. To connect to a specific site, you must know your IP address, but you must know its URL. The DNS gets the mappings of IP addresses and names.

Names and numbers

DNS converts machine names (eg www.xyz.com) IP addresses (eg 199.249.150.9). Basically, it translates from a name to an address and an address to a name.

The assignment of the IP address of the hostname is called reverse mapping. Http: / www.xyz.com / when you type in your browser, the browser must first obtain the IP address of www.xyz.com. The machine uses a directory service to look up IP addresses and this service is called DNS. When you enter your www.xyz.commachine first contacts a DNS server, asking it to find the IP address of www.xyz.com. This DNS server can contact other DNS servers on the Internet. DNS is therefore considered as the global network of servers. The great advantage of DNS is that no organization is responsible for its update. Is this called the distributed database.

The three-letter codes

A DNS server is a computer that is running the DNS software. The most popular DNS software, BIND (Berkeley Internet Name Domain) DNS is hierarchical, tree structured. The top is given by '. . And he called the root system. Directly under the root there are seven sub-domain nodes and these are immediately "with", "org", "gov", "thousand", "net", "edu ',' int ', etc.

DNS consists of two components

* Server Name
Addresses

Name Server:

This makes the task of finding names. Typically, there is a name server for a group of machines. If the server name does not contain the information requested, it will contact another nameserver. It is not necessary for all servers on how to contact each server. Every nameserver will know how to contact the root nameserver, and this, in turn, the location of every authoritative nameserver for all second level domains.

Decides

It works on a client machine to initiate DNS lookups. Contains a list of nameservers to use. As we read, the function of each of these nameservers is to resolve name queries. There are three types of nameservers nameserver server primary, secondary and cache name. The secondary nameservers are configured for backup purposes. Caching nameservers only resolve name queries but do not keep records of the DNS database. It is important to note that any change to primary nameservers should be sent to the secondary nameserver. This is because primary nameservers own databases. The changes are propagated through the "zone transfer.

HOW cache

DNS uses principle of "cache" for its operation. When a name server to receive information on a card, which stores this information. Further consultations for the assignment of using the cached result, thereby reducing search costs. The nameservers do not cache. The cache is a component called Time To Live (TTL) and the TTL determines how long a cache server to a piece of information. Thus, when the cache name servers receive an IP address, it receives the TTL with it. The cache name server IP address for the period of time, the pier.

When a process is to determine an IP address given a DNS address, calls on the local machine to resolve the address. This can be done in several ways:

Table look up. On UNIX hosts, the table is / etc / hosts.

The process communicates with the local name server. This is the name on a UNIX system.

By sending a massage to the remote system that identifies information in the file / etc / resolv.conf.

When a nameserver receives a query for a domain that does not work, you can return a reference to the client by specifying the name servers better. Usually working as a standard feature on the DNS server passes requests can not cope with a higher level server and so on, until the application can be processed, or the root of the namespace DNS is reached.

Name servers contain links to other nameserver with the help of which you can traverse the entire domain naming hierarchy. A host address with the original name of the server must be configured. After that, it can use DNS protocols to locate the nameserver responsible for all or part of the DNS hierarchy.

Thus when a nameserver receives a request, you can do one of the following:

You can answer the request with an IP address. This method is called iterative. In this, the client simply asks the server to resolve a domain name. The server accesses its database, finds its IP address and sends it back. If the server does not find the address, it returns a DNS error not found '). Contact another nameserver and try to find the IP address of the requested name. Return a reference to the client specifying the IP address of the server names.

Nslookup'is A User Interface People, called "available on the UNIX system. With this you can perform any DNS function. This program also shows the result for the user. Use is nslookup, you can get a list of all hosts in an area. To do this, you must first identify the nameserver for the zone.

The threats to the DNS are due to the lack of integrity and verify the authenticity of the information contained in the DNS. In addition, other protocols can use host names as a mechanism to control access. The Internet Engineering Task Force (IETF) has introduced the DNS Security (DNSSEC) extensions to DNS protocol.The main goal of DNSSEC is to provide authentication and integrity to the DNS. These are provided by the use of encryption "