as a recursive name server or recursive DNS, sometimes abbreviated as recdns. In principle, authoritative name servers suffice for the operation of the Internet. However, with only authoritative name-servers operating, every DNS query must start with recursive queries at the root zone of the Domain Name System and each user system must implement resolver software capable of recursive operation. Caching name server Caching name servers (DNS caches) store DNS query results for a period of time determined in the configuration (time-to-live) of each domain-name record. DNS caches improve the efficiency of the DNS by reducing DNS traffic across the Internet, and by reducing load on authoritative name-servers, particularly root name-servers. Because they can answer questions more quickly, they also increase the performance of end-user applications that use the DNS. Recursive name servers resolve any query they receive, even if they are not authoritative for the question being asked, by consulting the server or servers that are authoritative for the question. Caching name servers are often also recursive name servers—they perform every step necessary to answer any DNS query they receive. To do this the name server queries each authoritative name-server in turn, starting from the DNS root zone. It continues until it reaches the authoritative server for the zone that contains the queried domain name. That server provides the answer to the question, or definitively says it can't be answered, and the caching resolver then returns this response to the client that asked the question. The authority, resolving and caching functions can all be present in a DNS server implementation, but this is not required: a DNS server can implement any one of these functions alone, without implementing the others. Internet service providers typically provide caching resolvers for their customers. In addition, many home-networking routers implement caching resolvers to improve efficiency in the local network. Some systems utilize nscd, which stands for the "name service caching daemon". See also BIND Comparison of DNS server software Trojan.Win32.DNSChanger Domain Name System Security Extensions Lightweight Directory Access Protocol Network Information Service Name Service Switch (NSS) resolver, resolv.conf, resolvconf for Unix/Linux Open Root Server Network RealNames List of managed DNS providers Public recursive name servers References External links Free and Public DNS Servers, article on about.com by Tim Fisher, retrieved on 2015-02-08 21-59 UTC DNS & BIND Resources Internet Protocol based network software Domain Name System de:Domain Name System#Nameserver