IDN (Internationalized Domain Name), also known as multilingual domain name, refers to such domain names that contain non-ASCII characters in the domain name labels. For example, domain names that contain Japanese characters are Japanese domain names, and those containing Chinese characters are Chinese domain names. Initially, only 63 ASCII characters (“a-z”, “A-Z”, “0-9”, “-”) were applied in domain names, such as www.cnnic.cn. With the rapid development of Internet in non-English-speaking countries in the late 1990s, the Internet Community proposed to adopt native languages to the representation of domain names to substitute 63 ASCII characters that were previously in use, which presented demand for multilingual domain name or internationalized domain name. In March 2003, IETF (The Internet Engineering Task Force) issued three core technical standards on IDN, namely, RFC3490, RFC3491 and RFC3492, laying a foundation for the technological system of IDN.　Since 2008, IETF had contributed to updating updating the IDN protocol to address the problems encountered in IDN standardization process and released 5 new IDN protocols of RFC5890，RFC5891，RFC5892，RFC5893 and RFC5894 in total on August 5, 2010.