Name Resolution Model
A version of this page is also available for
4/8/2010
A namespace refers to the capability to associate the protocol and addressing attributes of a network service with one or more human-friendly names. Many namespaces are currently in wide use, including the Internet's Domain Name System (DNS), Microsoft Active Directory®, the bindery and Netware Directory Services (NDS) from Novell, X.500. These namespaces vary widely in how they are organized and implemented. Some of their properties are particularly important to understand to understand Winsock name resolution.
The following types of namespaces help determine how a service can be registered:
- Dynamic
- Static
- Persistent
Dynamic namespaces allow services to register with the namespace on the fly, and for clients to discover the available services at run-time. Dynamic namespaces frequently rely on broadcasts to indicate the continued availability of a network service. Examples of dynamic namespaces include the SAP namespace used within a Netware environment and the NBP namespace used by AppleTalk.
Static namespaces require all of the services to be registered ahead of time, that is, when the namespace is created. The DNS is an example of a static namespace. Although there is a programmatic way to resolve names, there is no programmatic way to register names.
Persistent namespaces allow services to register with the namespace on the fly. Unlike dynamic namespaces however, persistent namespaces retain the registration information in non-volatile storage where it remains until such time as the service requests that it be removed. Persistent namespaces are typified by directory services such as X.500 and the NDS. These environments allow the adding, deleting, and modification of service properties. In addition, the service object representing the service within the directory service could have a variety of attributes associated with the service. The most important attribute for client applications is the service's addressing information.