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DNS and Name Resolution

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  #1  
Old 06-02-2011
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DNS and Name Resolution
  

A domain is a name on the Internet, easy to remember and allows us to visit web pages or send email. This name is usually composed of two words separated by a dot. Internet names are hierarchical from right to left. Technically speaking, a domain allows us to identify computers on the Net This is made possible by the Domain Name System (DNS), which is responsible to find which computer connected to the Internet is the domain. Each computer on the Internet has its own IP address. Although it is sufficient to identify a machine when it comes to transmit packets, it does not is particularly convenient to use. It is easier to identify a machine by name, if it is moved for example.

Therefore, a machine receives a name that is more descriptive than the IP address. In the TCP / IP network stations are addressed by IP address. The IP address in binary form is a 32-bit sequence of 1's and 0's. This allows digital processing operating electronic circuits and programs de IP addresses quickly. But neither the 32-bit sequence, or the IP address for the human brain to grasp and easy to remember. The man used to prefer to name one thing and identified. This fact is reflected in the 70's in the ARPANET, the original predecessor of the Internet with. Instead of IP addresses names were used for addressing computers. These were easier to remember people and understand. To date, however, it is not possible to discuss a computer directly with his name on the network. For him, the world still consists of bits and bytes. And that's why he always needs a binary address. For this reason, several methods have been developed to implement a name resolution of names into numeric addresses.

Hosts : Each TCP / IP operating system has a file named hosts. In it, the IP addresses and names are listed in tabular form.

lmhosts : The lmhosts file is found exclusively in Windows operating systems. In addition to the IP addresses there NetBIOS names are mentioned.

DNS - Domain Name System : DNS is a server-based structure to resolve names to IP addresses. The client, who claims to have resolved a DNS name to an IP address makes a request to the DNS server. The DNS server manages IP addresses and associated names in a database. If a name is not mentioned there, he interviewed a parent DNS server that can be delivered to an IP address to the requesting client back.

WINS - Windows Internet Name Service : WINS is a platform-dependent, on Windows-based, system for name resolution. It builds on the NetBIOS service on the Windows operating systems. WINS was introduced to reduce the NetBIOS name resolution round awards. As with DNS the client accesses to the WINS server to convert a name to an IP address.

Expiration of a name resolution :
  • First, the client checks its local cache to see if an address exists for the name.
  • If not, he looks in the file hosts.
  • Does he even there is not the name he a query to the DNS server.
Additional name resolution in Windows :
  • The search will find the DNS server's IP address not the WINS server is consulted.
  • Also knows that his name yet to be sold a NetBIOS broadcast message.
  • The last straw for NetBIOS name resolution is the lmhosts file.
The Name resolution is the mechanism by which the IP address of an interface is replaced with its corresponding mnemonic. It is based on the settings contained in special files. When there must be a name resolution, such as when you specify an address on a web page, the system checks in sequence, the contents of the following files :
  • / Etc / hosts
  • / Etc / resolv.conf
Name Server

The terminals of the said domain name server can establish the correspondence between the domain name and IP address of a network of terminals. Each domain has a domain name server, known as the primary name server (primary domain name server) and a secondary name server (secondary domain name server) that allows you to replace the primary name server in case of unavailability . Each name server is declared in a server domain names one level higher, which allows an implicit delegation of authority over the domains. The naming system is a distributed architecture, where each entity is responsible for managing the domain name. There is therefore a body which has the task of managing all domain names.

Servers corresponding to the highest level domains (TLDs) are called "root name servers." There are thirteen, distributed worldwide under the names "a.root-servers.net 'to m.root-servers.net. A name server defines a zone, a set of domains on which the server has authority. The domain name system is transparent to the user, however, do not forget the following points:
  • Each computer must be configured with the address of a terminal capable of turning your name into an IP address. This terminal is called the Domain Name Server. Do not panic when you connect to the Internet, the access provider automatically changes your network settings to provide you with these name servers.
  • The IP address of a second domain name server (secondary Domain Name Server) must also be defined: the secondary name server can replace the primary name server in case of failure of the first.

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Old 06-02-2011
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Re: DNS and Name Resolution

A DNS server can be of various types. The one is Authoritative Server. A DNS authoritative for a given area contains all data related to areas falling within its competence. To service the more invulnerable to failures is generally recommended to support (redundancy) areas to one or more secondary servers (called slaves). The server maintains the master copies of zone files is called master or primary server. The secondary or slave server updates its zone file from another server through a process called zone transfer. The zone file contains a serial number that is incremented each time the file undergoes a change in this way, the slave server will recognize the changes.
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Old 06-02-2011
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Re: DNS and Name Resolution

Have you heard about Caching Server. This is also known as Recursive Server makes recursive lookups on behalf of local clients and also keeps a cache of recent requests made so that the replication of the requests would not need to reach out for resolution. This has the effect of lower bandwidth and therefore also faster in their responses. Since this type of DNS is completely independent of the other is about the implementation in networks protected by firewalls.
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