To identify any entity, a computer or any other resource like printer or a website hosted on a server, connected to an Internet, the Domain Name System is used. Each resource connected to the network is assigned a unique IP address to identify it. This uniquely identifies the connection of a host to the Internet. However, people prefer to use names instead of addresses. Just imagine If you have to type 192.168.010.010, instead of your website name to access it. Not only it will be difficult to remember but also is difficult to maintain. There for a mapping system is created to convert physical IP addresses to a more convenient Logical Names. This system is called Domain Name System (DNS). The logical name for a website is called Domain Name.
When Internet was small, mapping was done using a host file. The host wile had only two columns comprising name and address. Every host could store host file on a disk and update it periodically from a master host file. When a program or a user wanted to map a name to an address, the host consulted the host file and found the mapping.
Today, however, it is impossible to have one single host file to relate every address with a name and vice versa. the host file would be too large to store in every host. In addition, it would be impossible to update all the host files in the world every time there is a change.
One solution would be to store the entire host file in a single computer and allow access to this centralized information to every computer that needs mapping. But we know that this would create a huge amount of traffic on the IInternet.
Another solution, the one used today, is to divide this huge amount of information into smaller parts and store each part on a different computer. In this method, the host that needs mapping can contact the closest computer (in a data center) holding the mapping information.
Name Space
To be unambiguous, the names assigned to the resources (machines and websites), should be carefully selected from a name space with complete control over the binding between the names and IP addresses. In other words, the names should be unique because addresses are unique. A name space that maps each address to a unique name an be organized i two ways: flat and hierarchical.
Flat Name Space
In a Flat name space, a name is assigned to an address. A name in this space is a sequence of characters without structure. The names may or may not have a common section; if they do, it has no meaning. the main disadvantage of a flat name space is that it cannot be used in large system such as the Internet because it must be centrally controlled to avoid ambiguity and duplication.
Hierarchical Name Space
In a Hierarchical name space, each name is made up of several parts. the first part can define the nature of organization, the second part can define the name of an organization, the third part can define departments in an organization, and so on. In this case, the authority to control and assign the namespaces can be decentralized. A central authority can assign the part of the name that defines the nature of organization and the name of the organization. The responsibility of rest of the name can be given to organization itself. The organization can add suffixes (or prefixes) to the name to define its host or resources.
The management of the organization need not to worry that the prefix chosen for a host is taken by another oorganization because, even if part of an address is the same, the whole address is different. For example, assume two colleges and company calls one of their computers challenger. The first college is given a name by central authority such as fhda.edu, the second college is given the name berkeley.edu , and the company is given the name smart.com. When each of these organizations add the name challenger to the name they have already been given, the end result is three distinguishable names: challenger.fhda.edu, challenger.berkeley.edu, and challenger.smart.com. The names are unique without the need to be assigned by a central authority. The central authority controls only the part of the name, not the whole.
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When Internet was small, mapping was done using a host file. The host wile had only two columns comprising name and address. Every host could store host file on a disk and update it periodically from a master host file. When a program or a user wanted to map a name to an address, the host consulted the host file and found the mapping.
Today, however, it is impossible to have one single host file to relate every address with a name and vice versa. the host file would be too large to store in every host. In addition, it would be impossible to update all the host files in the world every time there is a change.
One solution would be to store the entire host file in a single computer and allow access to this centralized information to every computer that needs mapping. But we know that this would create a huge amount of traffic on the IInternet.
Another solution, the one used today, is to divide this huge amount of information into smaller parts and store each part on a different computer. In this method, the host that needs mapping can contact the closest computer (in a data center) holding the mapping information.
Name Space
To be unambiguous, the names assigned to the resources (machines and websites), should be carefully selected from a name space with complete control over the binding between the names and IP addresses. In other words, the names should be unique because addresses are unique. A name space that maps each address to a unique name an be organized i two ways: flat and hierarchical.
Flat Name Space
In a Flat name space, a name is assigned to an address. A name in this space is a sequence of characters without structure. The names may or may not have a common section; if they do, it has no meaning. the main disadvantage of a flat name space is that it cannot be used in large system such as the Internet because it must be centrally controlled to avoid ambiguity and duplication.
Hierarchical Name Space
In a Hierarchical name space, each name is made up of several parts. the first part can define the nature of organization, the second part can define the name of an organization, the third part can define departments in an organization, and so on. In this case, the authority to control and assign the namespaces can be decentralized. A central authority can assign the part of the name that defines the nature of organization and the name of the organization. The responsibility of rest of the name can be given to organization itself. The organization can add suffixes (or prefixes) to the name to define its host or resources.
The management of the organization need not to worry that the prefix chosen for a host is taken by another oorganization because, even if part of an address is the same, the whole address is different. For example, assume two colleges and company calls one of their computers challenger. The first college is given a name by central authority such as fhda.edu, the second college is given the name berkeley.edu , and the company is given the name smart.com. When each of these organizations add the name challenger to the name they have already been given, the end result is three distinguishable names: challenger.fhda.edu, challenger.berkeley.edu, and challenger.smart.com. The names are unique without the need to be assigned by a central authority. The central authority controls only the part of the name, not the whole.
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- Domain Name Space
Nice share, i would like to share my views in this. DNS means Domain name Server or Domain name system.DNS helps to convert the ip address into domain name.Domain name into ip address.You cannot remember many website ip address at same time.So domain name is used for remembering the website.
ReplyDeleteFor example 74.125.239.17 is one ip address of Google.com.It is very difficult to remember always.So you can use domain name to view the particular website.The primary work of DNS is if you give ip address in browser ,it search for domain name of particular ip address.If you give domain name in the address bar of the browser it convert the domain name to ip address(Search for the particular ip address). DNS consist of many resource records.Some of them are A record,CNAME record,DNAME record etc., You can check domain to ip ,Ip to domain and DNS query using the site WhoisXY.com