ehow Introduction connected to that category. The gTLDs are administered by Internet Corporation for Assigned Names and Numbers (ICANN). At the time of writing, 21 unique gTLDs exist. However, ICANN has an ongoing new gTLD process in which new gTLDs are evaluated for approval. Almost two thousand unique applications were received by ICANN during the application window [27]. ccTLDs indicate a country, or a territory as defined in the ISO-3166 [28], and the ccTLDs consist of two-character strings defined in the same standard. The ccTLDs are usually operated and owned by the government of the country or territory, a government agency, or an organization appointed by the local government. (There are two-character TLDs that are used like gTLDs and might even be owned by companies. For instance, these include tv. However, these are originally ccTLDs that have either been sold, or are just used in gTLD manner.) Infrastructure (TLD) is the arpa TLD. IANA administers arpa for the Internet Engineering Task Force (IETF) for technical purposes as a part of the Internet's infrastructure. The arpa TLD is used, for example, for DNS reverse queries RFC 3172 [45] - mapping IP addresses to DNS names. 1.6.4 Internationalized Domain Names Originally, the DNS supported only latin characters. This, obviously, had its origins in the birth of Internet in the USA, and in the challenges with computer systems of taking as input, and reproducing other character sets. However, modern computing can support many more scripts. In addition, the Internet has become a global phenomenon where most of its users are not native English speakers, or even use the latin script. Therefore, the IETF has specified the support for Internationalized Domain Names (IDNs) [29-32]. The IDNs started off in second level domains under different TLDs. In addition, the ICANN ccTLD Fast Track process enabled certain ccTLD IDN variants to be accepted to the root. It is expected that multiple IDN gTLDs will be introduced by the new gTLD process. IPv4 Address Exhaustion A