This Recommendation specifies general arrangements for interworking between the Internet and Public Data Networks (PDNs) among which PSPDN and FRPDN are considered. Three possible cases are defined: ? the case where the IP-TE connected to the PDN accesses the Internet via the PDN (access case); ? the case where two Internet subnetworks are concatenated via the PDN (Concatenation case 1); ? the case where two PDNs are concatenated via the Internet (Concatenation case 2). The following arrangements are specified in this Recommendation: 1) reference configuration; 2) interface characteristics for UNI and NNI; 3) addressing mechanism; 4) functionality of the Access Unit (AU)@ InterWorking Function (IWF) and the Adapter.