Bearer services and teleservices as described in the 1.20-Series Recommendations are the objects which network and
service providers offer to their customers.
ITU-T I.350 (REV 1)-1993 history
1993ITU-T I.350 (REV 1)-1993 General Aspects of Quality of Service and Network Performance in Digital Networks, Including ISDNs (Study Group XVIII) 16 pp