Info about Servers
Name server
A host used to resolve fully qualified domain names (FQDNs) into their associated Internet Protocol (IP) addresses.
Name servers are hosts on the Internet (or on large IP internetworks) that can be used to resolve host names into IP addresses, a process known as a name lookup. Name servers are an essential part of the Domain Name System (DNS). Because of name servers, when you want to access or reference a host on a TCP/IP network, you can use its friendly DNS name instead of its IP address, which is generally harder to remember.
The distributed system of name servers positioned at various locations around the Internet makes it possible to share the load of name resolution among many such servers instead of relying on a single server. Just imagine if one machine had to track the name of every host on the Internet-not only would its hardware requirements be astronomical, but it also would represent a single point of failure for the entire Internet economy!
DNS operates as a client/server-based system, with name servers forming the server part and resolvers forming the client part. Each name server has authority over a portion of DNS namespace known as a zone, which means that the name server can resolve name lookups for hosts located within that zone. A resolver sends a name lookup request to a name server by passing it the DNS name of a host on the network. The name server performs name resolution by determining the IP address that corresponds to the requested host's name. Name servers can also refer such queries to other name servers if they cannot answer them themselves, so a typical name lookup from a resolver might involve obtaining responses from several name servers in sequence.
Each zone has one name server called the master name server that is authoritative over hosts located in the zone. In addition, name servers can be classified on the basis of how they store zone information:
• Primary name servers:
These name servers keep a local file of the information relating to their zone. This local file or DNS database contains resource records, which are mappings of host names to IP addresses for hosts in that zone. A DNS administrator must generally create and maintain the DNS database manually on a primary name server, although with Dynamic DNS (DDNS) hosts can automatically register this information with name servers. Microsoft Windows 2000 and Windows .NET Server support DDNS.
• Secondary name servers:
These name servers obtain their database of resource records from a master name server, which can be either a primary name server or another secondary name server. The process by which the DNS database is transferred from a master name server to a secondary name server is known as zone transfer. Secondary name servers are provided mainly for fault tolerance and load balancing.