Top Level Domains (tlds) are the last part(s) of the host name in a DNS system. TLDs are managed by the Internet Assigned Numbers Authority. IANA divides tlds into three. infrastructure, generic(such as "com", "edu") and country code tlds(such as "en", "de" , "tr", ). Indexing the top level domain and optionally boosting is needed for improving the search results and enhancing locality.