INTERNATIONAL TELECOMMUNICATION UNION ITU-T RECOMMENDATION SUMMARY Rec. No. : I.233.1 Title : ISDN Frame relaying bearer service Study Group : XVIII - ISDN Version : New Date of adoption : 1991 Notes : Published with I.233 Recommendation I.210 describes the principles for defining telecommunication services supported by an ISDN including the concept of bearer services, teleservices and supplementary services. It also provides the means for the definition and description of such services. The purpose of Recommendation I.233.1 is to describe the frame relaying bearer service and to recommend the method of its provision in an ISDN. The definition and description of this service form the basis to define the network capabilities required for the support of the service in an ISDN. According to Recommendation I.210 a stage 1 service description uses three steps: prose description, static description and dynamic description. These steps are used in Recommendation I.233.1. The frame relaying bearer service provides the bidirectional transfer of service data units (SDU) from one S or T reference point to another with the order preserved. The service data units are routed through the network by appropriate layer 2 PDUs on the basis of an attached label. This label is a logical identifier with local significance [termed DLCI (data link connection identifier) in the protocol description]. The user network interface structure at the S or T reference point allows for the establishment of multiple virtual calls and/or permanent virtual circuits to many destinations. This service is generally available on the following ISDN access arrangements: point-to-multipoint (passive bus) and point-to-point (NT2). To order the complete text of this Recommendation, please use the Order Form for ITU-T Recommendations. An electronic version of this form is available on ITUDOC (Winword 2.0: UPI=ITU-5265; ASCII: UPI=ITU-2488).