Note: Many topics at this site are reduced versions of the text in "The Encyclopedia of Networking and Telecommunications." Search results will not be as extensive as a search of the book's CD-ROM.

SLP is an Internet protocol that is designed to make it easy for network clients to discover the available services on a network and learn information about the configuration of those services. Users don't need to know the name of a host that provides a service. Instead, they can query for a particular type of service and SLP will locate that service and return a network address. The protocol allows users to find network devices that perform specific functions, such as a printer that provides double-sided color printing.

SLP has become important for VoIP (Voice over IP), where SLP can be used by SIP (Session Initiation Protocol) clients to query for available services. SIP is an Internet signaling protocol used for setting up, maintaining, and terminating multimedia sessions such as voice calls and videoconferences. With SLP, clients query to find services based on the characteristics of those services. Similar services are described under "Service Advertising and Discovery."

The IETF's Service Location (srvloc) Working Group is developing SLP. SLP is defined in RFC 2165 (Service Location Protocol, June 1997) and updated in RFC 2608 (Service Location Protocol, Version 2, June 1999). A related document is RFC 2609 (Service Templates and Service Schemes, June 1999), which describes "service URLs." Service URLs include attributes that define services. Also see RFC 2614 (An API for Service Location, June 1999), RFC 3059 (Attribute List Extension for the Service Location Protocol, February 2001), and RFC 3082 (Notification and Subscription for SLP, March 2001).