This Recommendation contains the general service and operational principles to be followed for the international public data transmission service. The general model of international public data transmission service is outlined. This Recommendation includes important aspects of data transmission service - addressing, quality of service, call progress signals, multicast operation, user classes of service and optional user facilities. The general provisions between Administrations and the general provisions between the Administration and the customer are also described. The overview of the interrelationship between the relevant Recommendations necessary for offering data transmission service is in the scope of this Recommendation.