This article describes an Apple technology named Network Services Location Technology (NSL), introduced with Mac OS 8.5, that greatly aids and simplifies the search for TCP/IP-based network resources such as http and ftp servers.

When Apple introduced the Chooser and AppleTalk, they offered unprecedented ease of use by allowing users to browse for network services such as printers and file servers. With the introduction of the Network Services Location (NSL) Technology, Apple is bringing that ease-of-use to the Internet by providing the ability to browse through Internet services such as FTP and HTTP via TCP/IP similarly to the way users traditionally browse for AppleTalk services using the Chooser. By adopting this technology, applications can provide a better end user experience for users looking for network services.

The NSL is made up of a Manager and a set of plug-ins that gather data via particular network protocols such as DNS. The NSL Manager provides a single application programming interface (API) across any number of resource discovery protocols, and by developing additional plug-ins, additional methods for resource discovery can be added to NSL with no additional work on the part of the application developer.

What Is NSL?

The Network Services Location Manager provides a protocol-independent way for applications to discover available network services with minimal network traffic. The NSL Manager provides:

• AppleTalk-like ease of use for the dynamic discovery of traditional and non-traditional network services.
• Support for accepted and proposed industry standards, including Domain Name Service (DNS) and Service Location Protocol (SLP). SLP is an emerging standard (see RFC 2165) for registering and finding Internet services dynamically.
• A flexible, expandable architecture that can be easily leveraged by client and server applications.