Scope and field of application Network operations@ administration and maintenance (OA and M) applications need to be able to operate over a variety of networks@ including public data networks. This Recommendation describes the interworking between CCSN and packet switched public data networks (PSPDNs)@ which may be needed for the transmission of operational information between Administrations@ as a means of data transmission between operational centres and/or terminals for those Administrations. It should be noted that@ when dealing with OA and M protocols@ a great confusion may appear between: - the network which is used to convey the OA and M information (e.g. CCSN or PDN in Figure 1/X.326 above); - the network which is controlled by the CCSN@ with the support of the OA and M applications. It may furthermore happen that the controlled network interwork with a PDN@ as illustrated in the following Figure 2/X.326. Such an interworking is not considered as interworking between CCSN and PDN; consequently it is not described in the present Recommendation.