Basic Internet Architecture 67
Local name servers are manually configured to know the IP address of at least one root name server, and possibly another name server further up the domain name tree. Name servers either answer queries with local knowledge, or seek out another name server who is responsible for mappings higher up the domain name hierarchy. Local knowledge is often held in a cache built from recent queries from other hosts – the cache allows rapid answers for frequently resolved domain names.
For the curious reader: Many recent versions of Windows, and Unix-link operating systems such as Linux and FreeBSD have a tool called nslookup. Often installed as a command line application, nslookup allows you to manually perform DNS queries and explore your local network’s DNS configuration. Similar tools may be found under names like dig or host.
[RFC793] J. Postel, Ed, “Transmission Control Protocol”, RFC 793. September 1981.
[RFC1591] J. Postel, “Domain Name System Structure and Delegation”, RFC 1591. March 1994.
[RFC1771] Y. Rekhter, T. Li, “A Border Gateway Protocol 4 (BGP-4)”, RFC 1771. March 1995.
[RFC2050] K. Hubbard, M. Kosters, D. Conrad, D. Karrenberg, J. Postel, “Internet Registry IP Allocation Guidelines”, RFC 2050. November 1996.
[RFC2131] R. Droms, “Dynamic Host Configuration Protocol”, RFC 2131. March 1997.
[RFC2473] A. Conta, S. Deering, “Generic Packet Tunneling in IPv6 Specification”, RFC 2473, December 1998.
[RFC2616] R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee, “Hypertext Transfer Protocol – HTTP/1.1”, RFC 2616. June 1999.
 IEEE Std 802.3. “IEEE Standards for Local and Metropolitan Area Networks: Specific Requirements.
Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications”, 1998.