Naming and Directory Services (DNS, NIS, and LDAP)

A network information service enables machines to be identified by common namesinstead of numerical addresses. This makes communication simpler because users donot have to remember and try to enter cumbersome numerical addresses like192.168.0.0.For example, take a network of three machines that are named, pine, elm, and oak.Before pine can send a message to either elm or oak, pine must know theirnumerical network addresses. For this reason, pine keeps a file, /etc/hosts or/etc/inet/ipnodes, that stores the network address of every machine in thenetwork, including itself.pineelmoak/etc/hosts10.0.3.1 pine10.0.3.2 elm10.0.3.3 oakLikewise, in order for elm and oak to communicate with pine or with each other, themachines must keep similar files.pineelmoak/etc/hosts10.0.3.1 pine10.0.3.2 elm10.0.3.3 oak/etc/hosts10.0.3.1 pine10.0.3.2 elm10.0.3.3 oak/etc/hosts10.0.3.1 pine10.0.3.2 elm10.0.3.3 oakIn addition to storing addresses, machines store security information, mail data,network services information and so on. As networks offer more services, the liststored of information grows. As a result, each machine might need to keep an entireset of files which are similar to /etc/hosts or /etc/inet/ipnodes.22 System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP) • January 2005