What’s a TLD?
A top-level domain (TLD) is the suffix at the end of a domain name, such as “.com”, “.uk” and “.nz”. It represents the highest level division of the Domain Name System (DNS) hierarchy.
What’s the problem with acceptance of all TLDs?
The Internet is growing. In the 1980s and 1990s, the format of domain names followed a simple pattern. All domains ended with a small number of common 3 character long endings like “.com” and “.net”, or a two-letter code that represented a country like “.de” and “.uk”.
Times have changed. Since 2001, TLDs comprised of more than 3 characters long (think of “.info” or “.museum”) were introduced, and since 2010, non-Latin strings – known as internationalized domain names (IDNs) – have been added to the root zone. The ICANN Board’s approval of the new gTLD program in 2011 will allow for hundreds of additional TLDs to be added. This means that the variety of domain names will expand even further.
Software vendors, web site developers, and others might limit what they allow as a valid domain name in their applications. This might constrain the Internet’s growth, consumer choice and promotion of market competition on-line. The effort toward universal acceptance of domains seeks to ensure that the systems that perform domain name validation do it in a correct way that allows for all valid domains to function correctly. Domains should work regardless of the script they are written in or the time they were implemented: 20 years ago or yesterday.
To properly support today’s DNS, implementers need to deploy software and solutions that cater to all of these developments. Software needs to fully accept all the variety of domain names. This includes domain endings containing 4 or more characters and internationalized domain names.
What has changed?
No predetermined length. Until 2001, TLDs were either 2 or 3 characters long. This is no longer true. Does your software limit domain endings to a certain number of characters?
No fixed set of TLDs. In 2001, there were about 250 such endings. Now there are over 300. This will grow at a greater rate starting in 2013 as a result of the new gTLD program. Hundreds more TLDs are likely to be added to the root zone in the following years. Does your software have a hard-coded list of valid TLDs that it checks against? Is it regularly updated? Or does your application have a fixed drop-down box?
Non-Latin domains. Fields that accept domain names as input (such as email addresses, URLs, etc.) need to accept not just Latin but other encodings to work properly. Can your software correctly accept “испытание” if entered into a domain-related field?
Multiple representations. Non-Latin domains introduce a new idea – presentation and wire formats are different.
Source : ICANN