Recently, China Internet Network Information Center (CNNIC) officially released Secure Domain Name System（SDNS）, which provides the massive netizens with secure, intelligent and high-speed Internet access resolution service.
As the ccTLD registry, CNNIC has got almost twenty years' experience in domain name research & application and domain name resolution & operation. After release of Country Domain Name System (CDNS) in June 2011 offering the national domain name users with domain name resolution service (authoritative resolution) free of charge, CNNIC now presents the massive Internet end users with another service free of charge, namely, SDNS (recursive resolution). Relying on the three major technical strengths CNNIC accomplished from independent research and development of high-performance resolution software system, reliable Internet server cluster and professional operation monitoring platform, SDNS can further optimize netizens’ experience effectively through improving the Internet access resolution speed and minimizing unexpected DNS interruption or hijack. Meanwhile, SDNS can implement omni-directional real-time monitoring of resolution service status from the numerous data monitoring spots distributed nationwide on the ccTLD security monitoring platform, and also expand service capacity rapidly based on changes in user access quantity, thereby guaranteeing a continuous, reliable and stable service.　
Since Chinese domain name system is a multi-hierarchy and large-scale system under scattered management attribution, various attacks (i.e. cache poisoning, domain name hijack, DDoS attack, DNS amplification & reflection attacks, etc. ) on domain name resolution server pose a growing threat to Internet system security. High-efficient, secure and stable recursive resolution service is of great significance for normal operation of various Internet applications. SDNS employs the recursive resolution server software Zlope which is developed by CNNIC independently and can effectively prevent attacks on DNS by virtue of its favorable performance in security, high efficiency and ease for use. Up to now, nearly twenty patents have been applied for Zlope.
Upgrading of emerging Internet technologies like IPv6 and DNSSEC increases the complexity and risk of domain name service; therefore, overall reinforcement of Internet domain name security cannot be realized unless every aspect is incorporated because vulnerability of any aspect may have adverse impact on integral security performance. SDNS released by CNNIC this time further perfects the integral security of domain name resolution service system, effectively enhances public service system level of Internet, and boosts sound and orderly development of Internet security assurance system.
Address for SDNS:
Preferred DNS server: 1.2.4.8
Standby DNS server: 210.2.4.8
Please visit  http://www.sdns.cn for more information.

Domain name resolution:
To visit websites or any other Internet service, netizens need to finish progressive query of corresponding domain names in global Internet. Complete domain name resolution consists of four hierarchies: root domain name resolution, top-level domain name resolution, authoritative resolution and recursive resolution. CDNS previously released by CNNIC provides authoritative resolution service for registrants, while SDNS released this time presents Internet end users with recursive resolution service.