ITU-T M.729 PDF

General

Data transmissions may be made over the public switched telephone network in a manner similar to voice transmissions. Such data calls, while expected in most cases to be satisfactory, cannot always be assured success in view of the variety of routing and transmission characteristics that may be found in national extensions between international switching centers and user stations.

As the exact configuration of an international call is essentially impossible to determine without an extensive and complicated tracing process, some means must be specified to enable each Administration to investigate, as it considers necessary, reports of data transmission difficulties.