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The '''Second Level Domain''', or '''SLD''', is the portion of the [[URL]] that identifies the specific and unique owner. The SLD is the actual website's domain name.<ref>[http://www.build-your-website.co.uk/choosing-domain-name-second-level.htm SLD]</ref>
The '''Second Level Domain''', or '''SLD''', is the data directly before the top-level domain ([[TLD]]).<ref>[http://www.giantgeek.com/blog/?p=97 What is a SLD]</ref> For example, in www.example.com, “example” represents the second level domain, as the suffix "(dot)-com" represents the [[TLD]]. The SLD is generally the portion of the [[URL]] that identifies the website's domain name.<ref>[http://www.build-your-website.co.uk/choosing-domain-name-second-level.htm SLD]</ref> Usually, the SLD is determined and defined upon registration of a domain name. More than one SLD can function on the same [[Internet Protocol|IP]] Address.<ref>[http://help.godaddy.com/article/335 SLD Definition]</ref>


==Overview==
The DNS is composed of a tree-like hierarchy. Each TLD includes many second-level domains (such as "example" in "www.example.com"); each second-level domain can include a number of third-level domains ("www" in "www.example.com"), and so on.
The second domain level is the data directly before the top-level domain [[TLD]]. In the same way, the SLD represents the portion which is located exactly in the right part of the domain name extension. The SLD includes the [[TLD]] and helps during the identification process of a the owning organization of a specific [[URL]].<ref>[http://www.giantgeek.com/blog/?p=97 What is a SLD]</ref>
For example, in www.domainname.com, “domainname” represents the second level domain. Whereas the suffix "(dot)-com" represents the [[TLD]].  


Usually, the SLD is determined and defined upon registration of a domain name. More than one SLD can function on the same IP Address.<ref>[http://help.godaddy.com/article/335 SLD Definition]</ref>
==2LDs==
===ccSLDs===
Some countries restrict the second level under their [[ccTLD]]. These countries require that the second-level domain be one of several pre-determined second-level domains, generally indicating what type of individual or organization may register under that SLD. For these countries, you are not permitted to register domain names under the top level domain. It must be registered under one of the pre-determined second-level domains, called a ccSLD, or Country Code Second Level Domain.<ref>[http://www.quackit.com/domain-names/second-level_domain_names.cfm Second-Level Domain Names, quack-it.com]</ref>


Furthermore, a [[TLD]] can be separated into more SLDs; that is, second-level domains can be divided into sub-domains which could represent different computers within an organization or different aliases.
An example of this would be .co.uk, where .uk is the (cc)TLD and .co is the (cc)SLD. In this circumstance, the domain name ("example" in "example.co.uk") would be considered the third level domain, as it is in the third position.<ref>[http://www.igoldrush.com/reference/domain-glossary/c/ccsld-country-code-second-level-domain iGoldrush Domain Glossary]</ref> This can become confusing, as the domain name is commonly equated with the second level domain, and the [[subdomain]] is commonly equated with the third level domain. In these circumstances, the third level domain is sometimes referred to as a '''functional SLD'''.<ref>[http://tools.ietf.org/html/draft-ietf-provreg-dn-defn-00 Domain Name and Related Definitions, ietf.org]</ref>
 
There are also third-level domain names referred to as "provincial" domains, such as www.domainname.ab.com.
 
==Valid Domain Names and SLDs==
In order to register a domain name, the following features must be met:
* It may not contain more than 67 characters, including the domain name extension (such as .com).  
* It must use valid characters, which are those between 0-9, letters a-z and dashes, but the dash "-" cannot be used at the beginning or at the end of a domain name.<ref>[http://www.build-your-website.co.uk/choosing-domain-name-second-level.htm Choosing the right Domain Name]</ref>
 
==IDN==
By means of the [[IDN]] system, the valid set of characters has been expanded to include names and words written in native scripts; in this way, the domain names can contain letters from non-ASCII scripts. The [[IDN]] fast track system was approved by [[ICANN]] in 2009, and was adopted by many registries that provide domain space.<ref>[http://www.icann.org/en/topics/idn/ ICANN and IDNA]</ref>


==References==
==References==

Latest revision as of 15:58, 7 January 2022

The Second Level Domain, or SLD, is the data directly before the top-level domain (TLD).[1] For example, in www.example.com, “example” represents the second level domain, as the suffix "(dot)-com" represents the TLD. The SLD is generally the portion of the URL that identifies the website's domain name.[2] Usually, the SLD is determined and defined upon registration of a domain name. More than one SLD can function on the same IP Address.[3]

The DNS is composed of a tree-like hierarchy. Each TLD includes many second-level domains (such as "example" in "www.example.com"); each second-level domain can include a number of third-level domains ("www" in "www.example.com"), and so on.

2LDs[edit | edit source]

ccSLDs[edit | edit source]

Some countries restrict the second level under their ccTLD. These countries require that the second-level domain be one of several pre-determined second-level domains, generally indicating what type of individual or organization may register under that SLD. For these countries, you are not permitted to register domain names under the top level domain. It must be registered under one of the pre-determined second-level domains, called a ccSLD, or Country Code Second Level Domain.[4]

An example of this would be .co.uk, where .uk is the (cc)TLD and .co is the (cc)SLD. In this circumstance, the domain name ("example" in "example.co.uk") would be considered the third level domain, as it is in the third position.[5] This can become confusing, as the domain name is commonly equated with the second level domain, and the subdomain is commonly equated with the third level domain. In these circumstances, the third level domain is sometimes referred to as a functional SLD.[6]

References[edit | edit source]