IISP
The Interim Interswitch Signaling Protocol (IISP) was a protocol devised to provide signaling between switches from multiple vendors
The significance of IISP is very small now that the Private Network-to-Network Interface (PNNI) is complete
There is no migration path from IISP to PNNI
IISP uses UNI 3.1 signaling procedures as does PNNI, but the switches using IISP are not peers (that is, one switch functions as a network node and the other as an end-station)
There is no support for the dynamic distribution of routing information (routing protocol) in IISP