http://www.rfc-editor.org/rfc/rfc4129.txt
RFC 4129: Digital Private Network Signaling System (DPNSS)/Digital Access Signaling System 2 (DASS 2) Extensions to the IUA Protocol, R. Mukundan, K. Morneault, N. Mangalpally2005-09-01T23:00:00-00:00This document defines a mechanism for backhauling Digital Private Network Signaling System 1 (DPNSS 1) and Digital Access Signaling System 2 (DASS 2) messages over IP by extending the ISDN User Adaptation (IUA) Layer Protocol defined in RFC 3057. DPNSS 1, specified in ND1301:2001/03 (formerly BTNR 188), is used to interconnect Private Branch Exchanges (PBX) in a private network. DASS 2, specified in BTNR 190, is used to connect PBXs to the PSTN. This document aims to become an Appendix to IUA and to be the base for a DPNSS 1/DASS 2 User Adaptation (DUA) implementation. [STANDARDS-TRACK]