Internationalized domain names
The permitted character set of the DNS prevented the representation of names and words of many languages in their native alphabets or scripts. ICANN has approved the Punycode-based Internationalized domain name (IDNA) system, which maps Unicode strings into the valid DNS character set. In 2009 ICANN approved the installation of IDN county code top-level domains. In addition, many registries of the existing TLDs have adopted IDNA. Name servers
The Domain Name System is maintained by a distributed database system, which uses the client-server model. The nodes of this database are the name servers. Each domain has at least one authoritative DNS server that publishes information about that domain and the name servers of any domains subordinate to it. The top of the hierarchy is served by the root nameservers, the servers to query when looking up (resolving) a top-level domain name (TLD).
Authoritative name server
An authoritative name server is a name server that gives answers that have been configured by an original source, for example, the domain administrator or by dynamic DNS methods, in contrast to answers that were obtained via a regular DNS query to another name server. An authoritative-only name server only returns answers to queries about domain names that have been specifically configured by the administrator.
An authoritative name server can either be a master server or a slave server. A master server is a server that stores the original (master) copies of all zone records. A slave server uses an automatic updating mechanism of the DNS protocol in communication with its master to maintain an identical copy of the master records.
Every DNS zone must be assigned a set of authoritative name servers that are installed in NS records in the parent zone.
When domain names are registered with a domain name registrar their installation at the domain registry of a top level domain requires the assignment of a primary name server and at least one secondary name server. The requirement of multiple name servers aims to make the domain still functional even if one name server becomes inaccessible or inoperable. The designation of a primary name server is solely determined by the priority given to the domain name registrar. For this purpose generally only the fully qualified domain name of the name server is required, unless the servers are contained in the registered domain, in which case the corresponding IP address is needed as well.
Primary name servers are often master name servers, while secondary name server may be implemented as slave servers.
An authoritative server indicates its status of supplying definitive answers, deemed authoritative, by setting a software flag (a protocol structure bit), called the Authoritative Answer (AA) bit in its responses. This flag is usually reproduced prominently in the output of DNS administration query tools (such as dig) to indicate that the responding name server is an authority for the domain name in question. Recursive and caching name server
In principle, authoritative name servers are sufficient for the operation of the Internet. However, with only authoritative name servers operating, every DNS query must start with recursive queries at the root zone of the Domain Name System and each user system must implement resolver software capable of recursive operation.
To improve efficiency, reduce DNS traffic across the Internet, and increase performance in end-user applications, the Domain Name System supports DNS cache servers which store DNS query results for a period of time determined in the configuration (time-to-live) of the domain name record in question. Typically, such caching DNS servers, also called DNS caches, also implement the recursive algorithm necessary to resolve a given name starting with the DNS root through to the authoritative name servers of the queried domain. With this function implemented in the name server, user applications gain efficiency in design and operation.
The combination of DNS caching and recursive functions in a name server is not mandatory, the functions can be implemented independently in servers for special purposes.
Internet service providers typically provide recursive and caching name servers for their customers. In addition, many home networking routers implement DNS caches and recursors to improve efficiency in the local network.DNS resolvers
The client-side of the DNS is called a DNS resolver. It is responsible for initiating and sequencing the queries that ultimately lead to a full resolution (translation) of the resource sought, e.g., translation of a domain name into an IP address.
A DNS query may be either a non-recursive query or a recursive query:
* A non-recursive query is one in which the DNS server provides a record for a domain for which it is authoritative itself, or it provides a partial result without querying other servers.
* A recursive query is one for which the DNS server will fully answer the query (or give an error) by querying other name servers as needed. DNS servers are not required to support recursive queries.
The resolver, or another DNS server acting recursively on behalf of the resolver, negotiates use of recursive service using bits in the query headers.
Resolving usually entails iterating through several name servers to find the needed information. However, some resolvers function simplistically and can communicate only with a single name server. These simple resolvers (called "stub resolvers") rely on a recursive name server to perform the work of finding information for them.
Wednesday, 24 March 2010
Structure of Domain name system
The domain name space
The domain name space consists of a tree of domain names. Each node or leaf in the tree has zero or more resource records, which hold information associated with the domain name. The tree sub-divides into zones beginning at the root zone. A DNS zone consists of a collection of connected nodes authoritatively served by an authoritative nameserver. (Note that a single nameserver can host several zones.)
Administrative responsibility over any zone may be divided, thereby creating additional zones. Authority is said to be delegated for a portion of the old space, usually in form of sub-domains, to another nameserver and administrative entity. The old zone ceases to be authoritative for the new zone.
[edit] Domain name formulation
The definitive descriptions of the rules for forming domain names appear in RFC 1035, RFC 1123, and RFC 2181. A domain name consists of one or more parts, technically called labels, that are conventionally concatenated, and delimited by dots, such as example.com.
* The right-most label conveys the top-level domain; for example, the domain name www.example.com belongs to the top-level domain com.
* The hierarchy of domains descends from right to left; each label to the left specifies a subdivision, or subdomain of the domain to the right. For example: the label example specifies a subdomain of the com domain, and www is a subdomain of example.com. This tree of subdivisions may consist of 127 levels.
* Each label may contain up to 63 characters. The full domain name may not exceed a total length of 253 characters. In practice, some domain registries may have shorter limits.
* DNS names may technically consist of any character representable in an octet (RFC 3696). However, the allowed formulation of domain names in the DNS root zone, and most other subdomains, uses a preferred format and character set. The characters allowed in a label are a subset of the ASCII character set, and includes the characters a through z, A through Z, digits 0 through 9, and the hyphen. This rule is known as the LDH rule (letters, digits, hyphen). Domain names are interpreted in case-independent manner. Labels may not start or end with a hyphen, nor may two hyphens occur in sequence.
* A hostname is a domain name that has at least one IP address associated. For example, the domain names www.example.com and example.com are also hostnames, whereas the com domain is not.
History of Domain name system
The practice of using a name as a humanly more meaningful abstraction of a host's numerical address on the network dates back to the ARPANET era. Before the DNS was invented in 1983, each computer on the network retrieved a file called HOSTS.TXT from a computer at SRI (now SRI International).The HOSTS.TXT file mapped names to numerical addresses. A hosts file still exists on most modern operating systems, either by default or through explicit configuration. Many operating systems use name resolution logic that allows the administrator to configure selection priorities for available DNS resolution methods.
The rapid growth of the network required a scalable system that recorded a change in a host's address in one place only. Other hosts would learn about the change dynamically through a notification system, thus completing a globally accessible network of all hosts' names and their associated IP addresses.
At the request of Jon Postel, Paul Mockapetris invented the Domain Name System in 1983 and wrote the first implementation. The original specifications appeared in RFC 882 and RFC 883 which were superseded in November 1987 by RFC 1034 and RFC 1035. Several additional Request for Comments have proposed various extensions to the core DNS protocols.
In 1984, four Berkeley students—Douglas Terry, Mark Painter, David Riggle and Songnian Zhou—wrote the first UNIX implementation, which was maintained by Ralph Campbell thereafter. In 1985, Kevin Dunlap of DEC significantly re-wrote the DNS implementation and renamed it BIND—Berkeley Internet Name Domain. Mike Karels, Phil Almquist and Paul Vixie have maintained BIND since then. BIND was ported to the Windows NT platform in the early 1990s.
BIND was widely distributed, especially on Unix systems, and is the dominant DNS software in use on the Internet. With the heavy use and resulting scrutiny of its open-source code, as well as increasingly more sophisticated attack methods, many security flaws were discovered in BIND. This contributed to the development of a number of alternative nameserver and resolver programs. BIND itself was re-written from scratch in version 9, which has a security record comparable to other modern Internet software.
The DNS protocol was developed and defined in the early 1980s and published by the Internet Engineering Task Force.
The rapid growth of the network required a scalable system that recorded a change in a host's address in one place only. Other hosts would learn about the change dynamically through a notification system, thus completing a globally accessible network of all hosts' names and their associated IP addresses.
At the request of Jon Postel, Paul Mockapetris invented the Domain Name System in 1983 and wrote the first implementation. The original specifications appeared in RFC 882 and RFC 883 which were superseded in November 1987 by RFC 1034 and RFC 1035. Several additional Request for Comments have proposed various extensions to the core DNS protocols.
In 1984, four Berkeley students—Douglas Terry, Mark Painter, David Riggle and Songnian Zhou—wrote the first UNIX implementation, which was maintained by Ralph Campbell thereafter. In 1985, Kevin Dunlap of DEC significantly re-wrote the DNS implementation and renamed it BIND—Berkeley Internet Name Domain. Mike Karels, Phil Almquist and Paul Vixie have maintained BIND since then. BIND was ported to the Windows NT platform in the early 1990s.
BIND was widely distributed, especially on Unix systems, and is the dominant DNS software in use on the Internet. With the heavy use and resulting scrutiny of its open-source code, as well as increasingly more sophisticated attack methods, many security flaws were discovered in BIND. This contributed to the development of a number of alternative nameserver and resolver programs. BIND itself was re-written from scratch in version 9, which has a security record comparable to other modern Internet software.
The DNS protocol was developed and defined in the early 1980s and published by the Internet Engineering Task Force.
Domain Name System
The Domain Name System (DNS) is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participants. Most importantly, it translates domain names meaningful to humans into the numerical (binary) identifiers associated with networking equipment for the purpose of locating and addressing these devices worldwide. An often used analogy to explain the Domain Name System is that it serves as the "phone book" for the Internet by translating human-friendly computer hostnames into IP addresses. For example, www.example.com translates to 192.0.32.10.
The Domain Name System makes it possible to assign domain names to groups of Internet users in a meaningful way, independent of each user's physical location. Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device. Internet domain names are easier to remember than IP addresses such as 208.77.188.166 (IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). People take advantage of this when they recite meaningful URLs and e-mail addresses without having to know how the machine will actually locate them.
The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed, fault tolerant, and helped avoid the need for a single central register to be continually consulted and updated.
In general, the Domain Name System also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.
Other identifiers such as RFID tags, UPC codes, International characters in email addresses and host names, and a variety of other identifiers could all potentially utilize DNS.
The Domain Name System also defines the technical underpinnings of the functionality of this database service. For this purpose it defines the DNS protocol, a detailed specification of the data structures and communication exchanges used in DNS, as part of the Internet Protocol Suite (TCP/IP).
The Domain Name System makes it possible to assign domain names to groups of Internet users in a meaningful way, independent of each user's physical location. Because of this, World Wide Web (WWW) hyperlinks and Internet contact information can remain consistent and constant even if the current Internet routing arrangements change or the participant uses a mobile device. Internet domain names are easier to remember than IP addresses such as 208.77.188.166 (IPv4) or 2001:db8:1f70::999:de8:7648:6e8 (IPv6). People take advantage of this when they recite meaningful URLs and e-mail addresses without having to know how the machine will actually locate them.
The Domain Name System distributes the responsibility of assigning domain names and mapping those names to IP addresses by designating authoritative name servers for each domain. Authoritative name servers are assigned to be responsible for their particular domains, and in turn can assign other authoritative name servers for their sub-domains. This mechanism has made the DNS distributed, fault tolerant, and helped avoid the need for a single central register to be continually consulted and updated.
In general, the Domain Name System also stores other types of information, such as the list of mail servers that accept email for a given Internet domain. By providing a worldwide, distributed keyword-based redirection service, the Domain Name System is an essential component of the functionality of the Internet.
Other identifiers such as RFID tags, UPC codes, International characters in email addresses and host names, and a variety of other identifiers could all potentially utilize DNS.
The Domain Name System also defines the technical underpinnings of the functionality of this database service. For this purpose it defines the DNS protocol, a detailed specification of the data structures and communication exchanges used in DNS, as part of the Internet Protocol Suite (TCP/IP).
Domain name transfer
A Domain name transfer is the process of changing the designated registrar of a domain name. ICANN has defined a Policy on Transfer of Registrations between Registrars The usual process of a domain name transfer is:
1. The end user verifies that the whois admin contact info is correct, particularly the email address; obtains the authentication code (EPP transfer code) from the old registrar, and removes any domain lock that has been placed on the registration.
2. The end user contacts the new registrar with the wish to transfer the domain name to their service, and supplies the authentication code.
3. The new registrar will contact the old registrar with this information.
4. The old registrar will contact the end user to confirm the authenticity of this request. The end user may have to take further action with the old registrar, such as returning to the online management tools, to re-iterate their desire to proceed, in order to expedite the transfer.
5. The old registrar will release authority to the new registrar.
6. The new registrar will notify the end user of transfer completion. The new registrar may have automatically copied over the domain server information, and everything on the website will continue to work as before. Otherwise, the domain server information will need to be updated with the new registrar.
After this process, the new registrar becomes the domain name's designated registrar. The process may take about five days. In some cases, the old registrar may intentionally delay the transfer as long as allowable. After transfer, the domain cannot be transferred again for 60 days, except back to the previous registrar.
It is unwise to attempt to transfer a domain immediately before it expires. In some cases, a transfer can take up to 14 days, meaning that the transfer may not complete before the registration expires. This could result in loss of the domain name registration and failure of the transfer. To avoid this, end users should either transfer well before the expiration date, or renew the registration before attempting the transfer.
If a domain registration expires, irrespective of the reason, it can be difficult, expensive, or impossible for the original owner to get it back. After the expiration date, the domain status often passes through several management phases, often for a period of months; usually it does not simply become generally available.
Transfer scams
With the introduction of SRS, many smaller registrars had to compete with each other. Some companies offered value added services or used viral marketing, while others, such as VeriSign and the Domain Registry of America attempted to trick customers to switch from their current registrar using a practice known as domain slamming.
Many of these transfer scams involve a notice sent in the mail, fax, or e-mail. Some scammers contacted end users by telephone (since the contact information is available through WHOIS) to obtain more information. These notices would include information publicly available from the WHOIS database to add to the look of authenticity. The text would include legalese to confuse the end user into thinking that it is an official binding notice. Scam registrars go after domain names that are expiring soon or have recently expired. Expired domain names do not have to go through the authentication process to be transferred, as the previous registrar would have relinquished management rights of the domain name. Domain name expiry dates are readily available via WHOIS.
1. The end user verifies that the whois admin contact info is correct, particularly the email address; obtains the authentication code (EPP transfer code) from the old registrar, and removes any domain lock that has been placed on the registration.
2. The end user contacts the new registrar with the wish to transfer the domain name to their service, and supplies the authentication code.
3. The new registrar will contact the old registrar with this information.
4. The old registrar will contact the end user to confirm the authenticity of this request. The end user may have to take further action with the old registrar, such as returning to the online management tools, to re-iterate their desire to proceed, in order to expedite the transfer.
5. The old registrar will release authority to the new registrar.
6. The new registrar will notify the end user of transfer completion. The new registrar may have automatically copied over the domain server information, and everything on the website will continue to work as before. Otherwise, the domain server information will need to be updated with the new registrar.
After this process, the new registrar becomes the domain name's designated registrar. The process may take about five days. In some cases, the old registrar may intentionally delay the transfer as long as allowable. After transfer, the domain cannot be transferred again for 60 days, except back to the previous registrar.
It is unwise to attempt to transfer a domain immediately before it expires. In some cases, a transfer can take up to 14 days, meaning that the transfer may not complete before the registration expires. This could result in loss of the domain name registration and failure of the transfer. To avoid this, end users should either transfer well before the expiration date, or renew the registration before attempting the transfer.
If a domain registration expires, irrespective of the reason, it can be difficult, expensive, or impossible for the original owner to get it back. After the expiration date, the domain status often passes through several management phases, often for a period of months; usually it does not simply become generally available.
Transfer scams
With the introduction of SRS, many smaller registrars had to compete with each other. Some companies offered value added services or used viral marketing, while others, such as VeriSign and the Domain Registry of America attempted to trick customers to switch from their current registrar using a practice known as domain slamming.
Many of these transfer scams involve a notice sent in the mail, fax, or e-mail. Some scammers contacted end users by telephone (since the contact information is available through WHOIS) to obtain more information. These notices would include information publicly available from the WHOIS database to add to the look of authenticity. The text would include legalese to confuse the end user into thinking that it is an official binding notice. Scam registrars go after domain names that are expiring soon or have recently expired. Expired domain names do not have to go through the authentication process to be transferred, as the previous registrar would have relinquished management rights of the domain name. Domain name expiry dates are readily available via WHOIS.
Designated registrar
An end-user cannot directly register a domain and manage their domain information with ICANN. A designated registrar must be chosen. Prior to 1999, the only com registrar was NSI, but the approval of the SRS opened up the opportunity for other companies to be designated as registrars.
Each ICANN-accredited registrar must pay a fixed fee of US$4,000 plus a variable fee. The sum of variable registrar fees is intended to total US$3.8 million.
Only the designated registrar may modify or delete information about a domain name. The competition that the SRS created enables end users to choose from many registrars offering different services at varying prices. It is not unusual for an end user to switch registrars which invokes a domain transfer process governed by specific domain name transfer policies.
When a registrar registers a com domain name for an end-user, it must pay a maximum annual fee of US$6.86 to VeriSign, the registry operator for com, and a US$0.20 administration fee to ICANN. Most domain registrars price their services and products to address both the annual fees and the administration fees that must be paid to ICANN. Barriers to entry into the bulk registrar industry are high for new companies without an existing customer base.[citation needed]
Many registrars also offer registration through reseller affiliates. An end-user registers either directly with a registrar, or indirectly through one or more layers of resellers. As of 2008, the cost generally ranges from a low of about $7.50 per year to about $35 per year. The maximum period of registration of a domain name is generally 10 years.
Some registrars are offering longer periods of up to one hundred years, but such offers involve the registrar renewing the registration for their customer. The one hundred year domain name registration would not be in the official registration database. Some packages of Internet services, such as web hosting, include the domain registration in the total package pricing.
Each ICANN-accredited registrar must pay a fixed fee of US$4,000 plus a variable fee. The sum of variable registrar fees is intended to total US$3.8 million.
Only the designated registrar may modify or delete information about a domain name. The competition that the SRS created enables end users to choose from many registrars offering different services at varying prices. It is not unusual for an end user to switch registrars which invokes a domain transfer process governed by specific domain name transfer policies.
When a registrar registers a com domain name for an end-user, it must pay a maximum annual fee of US$6.86 to VeriSign, the registry operator for com, and a US$0.20 administration fee to ICANN. Most domain registrars price their services and products to address both the annual fees and the administration fees that must be paid to ICANN. Barriers to entry into the bulk registrar industry are high for new companies without an existing customer base.[citation needed]
Many registrars also offer registration through reseller affiliates. An end-user registers either directly with a registrar, or indirectly through one or more layers of resellers. As of 2008, the cost generally ranges from a low of about $7.50 per year to about $35 per year. The maximum period of registration of a domain name is generally 10 years.
Some registrars are offering longer periods of up to one hundred years, but such offers involve the registrar renewing the registration for their customer. The one hundred year domain name registration would not be in the official registration database. Some packages of Internet services, such as web hosting, include the domain registration in the total package pricing.
History of Domain name registrar
Until 1999, Network Solutions (NSI) operated the com, net, and org registries. It was the domain name registry operator for these domains as well as the sole registrar. However, several companies had developed independent registrar services. One such company, NetNames, invented the idea of a commercial standalone domain name registration service in 1996. Registrars introducing the concept of domain name sales and other associated services, effectively introducing the retail model into the industry and assigning a wholesale role to the registries. NSI assimilated this model, which ultimately led to the separation of registry and registrar functions.
In October 1998, following pressure from the growing domain name registration business and other interested parties, NSI's agreement with the United States Department of Commerce was amended. This amendment required the creation of a shared registration system (SRS) that supported multiple registrars. This SRS officially opened on November 30, 1999 under the supervision of ICANN, though there had been several testbed registrars using the system since March 11, 1999. Since then, over 500 registrars have entered the market for domain name registration services.
Of the registrars who initially entered the market, many have continued to grow and outpace rivals. Go Daddy is the largest registrar. Other successful registrars include eNom, Tucows and Melbourne IT. Registrars who initially led the market but later were surpassed by rivals include Network Solutions and Dotster.
In October 1998, following pressure from the growing domain name registration business and other interested parties, NSI's agreement with the United States Department of Commerce was amended. This amendment required the creation of a shared registration system (SRS) that supported multiple registrars. This SRS officially opened on November 30, 1999 under the supervision of ICANN, though there had been several testbed registrars using the system since March 11, 1999. Since then, over 500 registrars have entered the market for domain name registration services.
Of the registrars who initially entered the market, many have continued to grow and outpace rivals. Go Daddy is the largest registrar. Other successful registrars include eNom, Tucows and Melbourne IT. Registrars who initially led the market but later were surpassed by rivals include Network Solutions and Dotster.
Domain name registrar
A domain name registrar is an organization or commercial entity, accredited by the Internet Corporation for Assigned Names and Numbers (ICANN) or by a national country code top-level domain (ccTLD) authority, to manage the reservation of Internet domain names in accordance with the guidelines of the designated domain name registries and offer such services to the public.
Prices of registration
Prices of domain registrations are set by each registry.
Third-level domains
Domain name registries may also impose a system of third-level domains on users. DENIC, the registry for Germany (.de), does not impose third level domains. AFNIC, the registry for France (.fr), has some third level domains, but not all registrants have to use them, and Nominet UK, the registry for the United Kingdom (.uk), requires all names to have a third level domain (e.g. .co.uk or .org.uk)
Domain Sub-Registration
Registrants of second-level domains sometimes act as a registry by offering sub-registrations to their registration. For example, registrations to .fami.ly are offered by the registrant of fami.ly and not by GPTC, the registry for Libya
Prices of domain registrations are set by each registry.
Third-level domains
Domain name registries may also impose a system of third-level domains on users. DENIC, the registry for Germany (.de), does not impose third level domains. AFNIC, the registry for France (.fr), has some third level domains, but not all registrants have to use them, and Nominet UK, the registry for the United Kingdom (.uk), requires all names to have a third level domain (e.g. .co.uk or .org.uk)
Domain Sub-Registration
Registrants of second-level domains sometimes act as a registry by offering sub-registrations to their registration. For example, registrations to .fami.ly are offered by the registrant of fami.ly and not by GPTC, the registry for Libya
Policies of domain registration
Allocation policies
Generally, domain name registries operate a first-come-first-served system of allocation but may reject the allocation of specific domains on the basis of political, religious, historical, legal or cultural reasons.
For example, in the United States, between 1996 and 1998, InterNIC automatically rejected domain name applications based on a list of perceived obscenities.
Registries may also control matters of interest to their local communities: for example, the German, Japanese and Polish registries have introduced internationalized domain names to allow use of local non-ASCII characters.
[edit] Dispute policies
Domains which are registered with ICANN registrars, generally have to use the Uniform Domain-Name Dispute-Resolution Policy (UDRP), however, Germany's DENIC requires people to use the German civil courts, and Nominet UK deals with Intellectual Property and other disputes through its own dispute resolution service.
Generally, domain name registries operate a first-come-first-served system of allocation but may reject the allocation of specific domains on the basis of political, religious, historical, legal or cultural reasons.
For example, in the United States, between 1996 and 1998, InterNIC automatically rejected domain name applications based on a list of perceived obscenities.
Registries may also control matters of interest to their local communities: for example, the German, Japanese and Polish registries have introduced internationalized domain names to allow use of local non-ASCII characters.
[edit] Dispute policies
Domains which are registered with ICANN registrars, generally have to use the Uniform Domain-Name Dispute-Resolution Policy (UDRP), however, Germany's DENIC requires people to use the German civil courts, and Nominet UK deals with Intellectual Property and other disputes through its own dispute resolution service.
Operation of domain registry
Some name registries are government departments (e.g., the registry for Sri Lanka nic.lk). Some are co-operatives of Internet service providers (such as DENIC) or not-for profit companies (such as Nominet UK). Others operate as commercial organizations, such as the US registry (nic.us).
The allocated and assigned domain names are made available by registries by use of the WHOIS system and via their Domain name servers.
Some registries sell the names directly (like SWITCH in Switzerland) and others rely on separate entities to sell them. For example, names in the .com TLD are in some sense sold "wholesale" at a regulated price by VeriSign, and individual domain name registrar sell names "retail" to businesses and consumers.
The allocated and assigned domain names are made available by registries by use of the WHOIS system and via their Domain name servers.
Some registries sell the names directly (like SWITCH in Switzerland) and others rely on separate entities to sell them. For example, names in the .com TLD are in some sense sold "wholesale" at a regulated price by VeriSign, and individual domain name registrar sell names "retail" to businesses and consumers.
Domain name registry
A domain name registry, is a database of all domain names registered in a top-level domain. A registry operator, also called a Network Information Center (NIC), is the part of the Domain Name System (DNS) of the Internet that keeps the database of domain names, and generates the zone files which convert domain names to IP addresses. Each NIC is an organisation that manages the registration of Domain names within the top-level domains for which it is responsible, controls the policies of domain name allocation, and technically operates its top-level domain. It is potentially distinct from a domain name registrar. [1]
Domain names are managed under a hierarchy headed by the Internet Assigned Numbers Authority (IANA), which manages the top of the DNS tree by administrating the data in the root nameservers.
IANA also operates the .int registry for intergovernmental organisations, the .arpa zone for protocol administration purposes, and other critical zones such as root-servers.net.
IANA delegates all other domain name authority to other domain name registries such as VeriSign.
Country code top-level domains (ccTLD) are delegated by IANA to national registries such as DENIC in Germany and Nominet in the United Kingdom.
Domain names are managed under a hierarchy headed by the Internet Assigned Numbers Authority (IANA), which manages the top of the DNS tree by administrating the data in the root nameservers.
IANA also operates the .int registry for intergovernmental organisations, the .arpa zone for protocol administration purposes, and other critical zones such as root-servers.net.
IANA delegates all other domain name authority to other domain name registries such as VeriSign.
Country code top-level domains (ccTLD) are delegated by IANA to national registries such as DENIC in Germany and Nominet in the United Kingdom.
Tuesday, 23 March 2010
obtaining hosting
Web hosting is often provided as part of a general Internet access plan; there are many free and paid providers offering these services.
A customer needs to evaluate the requirements of the application to choose what kind of hosting to use. Such considerations include database server software, scripting software, and operating system. Most hosting providers provide Linux-based web hosting which offers a wide range of different software. A typical configuration for a Linux server is the LAMP platform: Linux, Apache, MySQL, and PHP/Perl/Python. The webhosting client may want to have other services, such as email for their business domain, databases or multi-media services for streaming media. A customer may also choose Windows as the hosting platform. The customer still can choose from PHP, Perl, and Python but may also use ASP .Net or Classic ASP. Web hosting packages often include a Web Content Management System, so the end-user doesn't have to worry about the more technical aspects.
A customer needs to evaluate the requirements of the application to choose what kind of hosting to use. Such considerations include database server software, scripting software, and operating system. Most hosting providers provide Linux-based web hosting which offers a wide range of different software. A typical configuration for a Linux server is the LAMP platform: Linux, Apache, MySQL, and PHP/Perl/Python. The webhosting client may want to have other services, such as email for their business domain, databases or multi-media services for streaming media. A customer may also choose Windows as the hosting platform. The customer still can choose from PHP, Perl, and Python but may also use ASP .Net or Classic ASP. Web hosting packages often include a Web Content Management System, so the end-user doesn't have to worry about the more technical aspects.
Types of hosting
Internet hosting services can run Web servers; see Internet hosting services.
Hosting services limited to the Web:
Many large companies who are not internet service providers also need a computer permanently connected to the web so they can send email, files, etc. to other sites. They may also use the computer as a website host so they can provide details of their goods and services to anyone interested. Additionally these people may decide to place online orders.
Free web hosting service: offered by different companies with limited services, sometimes supported by advertisements, and often limited when compared to paid hosting.
Shared web hosting service: one's website is placed on the same server as many other sites, ranging from a few to hundreds or thousands. Typically, all domains may share a common pool of server resources, such as RAM and the CPU. The features available with this type of service can be quite extensive. A shared website may be hosted with a reseller.
Reseller web hosting: allows clients to become web hosts themselves. Resellers could function, for individual domains, under any combination of these listed types of hosting, depending on who they are affiliated with as a provider. Resellers' accounts may vary tremendously in size: they may have their own virtual dedicated server to a collocated server. Many resellers provide a nearly identical service to their provider's shared hosting plan and provide the technical support themselves.
Virtual Dedicated Server: also known as a Virtual Private Server (VPS), divides server resources into virtual servers, where resources can be allocated in a way that does not directly reflect the underlying hardware. VPS will often be allocated resources based on a one server to many VPSs relationship, however virtualisation may be done for a number of reasons, including the ability to move a VPS container between servers. The users may have root access to their own virtual space. Customers are sometimes responsible for patching and maintaining the server.
Dedicated hosting service: the user gets his or her own Web server and gains full control over it (root access for Linux/administrator access for Windows); however, the user typically does not own the server. Another type of Dedicated hosting is Self-Managed or Unmanaged. This is usually the least expensive for Dedicated plans. The user has full administrative access to the box, which means the client is responsible for the security and maintenance of his own dedicated box.
Managed hosting service: the user gets his or her own Web server but is not allowed full control over it (root access for Linux/administrator access for Windows); however, they are allowed to manage their data via FTP or other remote management tools. The user is disallowed full control so that the provider can guarantee quality of service by not allowing the user to modify the server or potentially create configuration problems. The user typically does not own the server. The server is leased to the client.
Colocation web hosting service: similar to the dedicated web hosting service, but the user owns the colo server; the hosting company provides physical space that the server takes up and takes care of the server. This is the most powerful and expensive type of web hosting service. In most cases, the colocation provider may provide little to no support directly for their client's machine, providing only the electrical, Internet access, and storage facilities for the server. In most cases for colo, the client would have his own administrator visit the data center on site to do any hardware upgrades or changes.
Cloud Hosting: is a new type of hosting platform that allows customers powerful, scalable and reliable hosting based on clustered load-balanced servers and utility billing. Removing single-point of failures and allowing customers to pay for only what they use versus what they could use.
Clustered hosting: having multiple servers hosting the same content for better resource utilization. Clustered Servers are a perfect solution for high-availability dedicated hosting, or creating a scalable web hosting solution. A cluster may separate web serving from database hosting capability.
Grid hosting: this form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes.
Home server: usually a single machine placed in a private residence can be used to host one or more web sites from a usually consumer-grade broadband connection. These can be purpose-built machines or more commonly old PCs. Some ISPs actively attempt to block home servers by disallowing incoming requests to TCP port 80 of the user's connection and by refusing to provide static IP addresses. A common way to attain a reliable DNS hostname is by creating an account with a dynamic DNS service. A dynamic DNS service will automatically change the IP address that a URL points to when the IP address changes.
Some specific types of hosting provided by web host service providers:
File hosting service: hosts files, not web pages
Image hosting service
Video hosting service
Blog hosting service
One-click hosting
Pastebin Hosts text snippets
Shopping cart software
E-mail hosting service
Hosting services limited to the Web:
Many large companies who are not internet service providers also need a computer permanently connected to the web so they can send email, files, etc. to other sites. They may also use the computer as a website host so they can provide details of their goods and services to anyone interested. Additionally these people may decide to place online orders.
Free web hosting service: offered by different companies with limited services, sometimes supported by advertisements, and often limited when compared to paid hosting.
Shared web hosting service: one's website is placed on the same server as many other sites, ranging from a few to hundreds or thousands. Typically, all domains may share a common pool of server resources, such as RAM and the CPU. The features available with this type of service can be quite extensive. A shared website may be hosted with a reseller.
Reseller web hosting: allows clients to become web hosts themselves. Resellers could function, for individual domains, under any combination of these listed types of hosting, depending on who they are affiliated with as a provider. Resellers' accounts may vary tremendously in size: they may have their own virtual dedicated server to a collocated server. Many resellers provide a nearly identical service to their provider's shared hosting plan and provide the technical support themselves.
Virtual Dedicated Server: also known as a Virtual Private Server (VPS), divides server resources into virtual servers, where resources can be allocated in a way that does not directly reflect the underlying hardware. VPS will often be allocated resources based on a one server to many VPSs relationship, however virtualisation may be done for a number of reasons, including the ability to move a VPS container between servers. The users may have root access to their own virtual space. Customers are sometimes responsible for patching and maintaining the server.
Dedicated hosting service: the user gets his or her own Web server and gains full control over it (root access for Linux/administrator access for Windows); however, the user typically does not own the server. Another type of Dedicated hosting is Self-Managed or Unmanaged. This is usually the least expensive for Dedicated plans. The user has full administrative access to the box, which means the client is responsible for the security and maintenance of his own dedicated box.
Managed hosting service: the user gets his or her own Web server but is not allowed full control over it (root access for Linux/administrator access for Windows); however, they are allowed to manage their data via FTP or other remote management tools. The user is disallowed full control so that the provider can guarantee quality of service by not allowing the user to modify the server or potentially create configuration problems. The user typically does not own the server. The server is leased to the client.
Colocation web hosting service: similar to the dedicated web hosting service, but the user owns the colo server; the hosting company provides physical space that the server takes up and takes care of the server. This is the most powerful and expensive type of web hosting service. In most cases, the colocation provider may provide little to no support directly for their client's machine, providing only the electrical, Internet access, and storage facilities for the server. In most cases for colo, the client would have his own administrator visit the data center on site to do any hardware upgrades or changes.
Cloud Hosting: is a new type of hosting platform that allows customers powerful, scalable and reliable hosting based on clustered load-balanced servers and utility billing. Removing single-point of failures and allowing customers to pay for only what they use versus what they could use.
Clustered hosting: having multiple servers hosting the same content for better resource utilization. Clustered Servers are a perfect solution for high-availability dedicated hosting, or creating a scalable web hosting solution. A cluster may separate web serving from database hosting capability.
Grid hosting: this form of distributed hosting is when a server cluster acts like a grid and is composed of multiple nodes.
Home server: usually a single machine placed in a private residence can be used to host one or more web sites from a usually consumer-grade broadband connection. These can be purpose-built machines or more commonly old PCs. Some ISPs actively attempt to block home servers by disallowing incoming requests to TCP port 80 of the user's connection and by refusing to provide static IP addresses. A common way to attain a reliable DNS hostname is by creating an account with a dynamic DNS service. A dynamic DNS service will automatically change the IP address that a URL points to when the IP address changes.
Some specific types of hosting provided by web host service providers:
File hosting service: hosts files, not web pages
Image hosting service
Video hosting service
Blog hosting service
One-click hosting
Pastebin Hosts text snippets
Shopping cart software
E-mail hosting service
Hosting reliability and uptime
Hosting uptime refers to the percentage of time the host is accessible via the internet. Many providers state that they aim for at least 99.9% uptime (roughly equivalent to 45 minutes of downtime a month, or less), but there may be server restarts and planned (or unplanned) maintenance in any hosting environment, which may or may not be considered part of the official uptime promise.
Many providers tie uptime and accessibility into their own service level agreement (SLA). SLAs sometimes include refunds or reduced costs if performance goals are not met.
Many providers tie uptime and accessibility into their own service level agreement (SLA). SLAs sometimes include refunds or reduced costs if performance goals are not met.
Service scope of web hosting
The scope of hosting services varies widely. The most basic is web page and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a Web interface. The files are usually delivered to the Web "as is" or with little processing. Many Internet service providers (ISPs) offer this service free to their subscribers. People can also obtain Web page hosting from other, alternative service providers. Personal web site hosting is typically free, advertisement-sponsored, or cheap. Business web site hosting often has a higher expense.
Single page hosting is generally sufficient only for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, Java, Ruby on Rails, ColdFusion, and ASP.NET). These facilities allow the customers to write or install scripts for applications like forums and content management. For e-commerce, SSL is also highly recommended.
The host may also provide an interface or control panel for managing the Web server and installing scripts as well as other services like e-mail. Some hosts specialize in certain software or services (e.g. e-commerce). They are commonly used by larger companies to outsource network infrastructure to a hosting company.
Single page hosting is generally sufficient only for personal web pages. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. PHP, Java, Ruby on Rails, ColdFusion, and ASP.NET). These facilities allow the customers to write or install scripts for applications like forums and content management. For e-commerce, SSL is also highly recommended.
The host may also provide an interface or control panel for managing the Web server and installing scripts as well as other services like e-mail. Some hosts specialize in certain software or services (e.g. e-commerce). They are commonly used by larger companies to outsource network infrastructure to a hosting company.
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