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.

PNNI is a link-state routing protocol for ATM networks that automatically finds paths in the network using neighbor discovery techniques and then assists in setting up SVCs (switched virtual circuits) between end systems. In this respect, PNNI is both a signaling and routing protocol. A signaling plane assists in setting up virtual circuits while routing functions provide a mechanism to route ATM cells between switches or autonomous ATM networks.

PNNI is an ATM Forum protocol that was designed using concepts borrowed from the Internet's OSPF link-state routing protocol. One of its primary features is the ability to support the integration of multivendor ATM switches. PNNI provides a standard signaling protocol so that multivendor ATM equipment can exchange topology information.

Note that PNNI is an abbreviation for "Private Network-to-Node Interface" or "Private Network-to-Network Interface." Node refers to an ATM switch. The two different names reflect the fact that PNNI works between two ATM switches in the same network or between separate, autonomous ATM networks.