The international CAS package (icas) provides an extension to the basic CAS packages, defining additional line signals and events required for international signalling protocols.
ITU-T H.248.28-2007 Referenced Document
ITU-T H.248.1-2005 Gateway Control Protocol: Version 3 Study Group 16 Audiovisual Services Systems and Multimedia System Infrastructure - Communications Procedures Study Group 16
ITU-T H.248.25-2007 Gateway control protocol: Basic CAS packages Study Group 16
ITU-T H.248.28-2007 history
2007ITU-T H.248.28-2007 Gateway control protocol: International CAS packages Study Group 16