INTERNATIONAL TELECOMMUNICATION UNION ITU-T RECOMMENDATION SUMMARY Rec. No. : X.612 Title : Provision of the OSI connection-mode network service by packet mode terminal equipment connected to an integrated services digital network (ISDN) for CCITT applications Study Group : VII - Data Communications Networks Version : New Date of adoption : 1990 Notes : Recommendation X.612 specifies the method of providing the OSI Connection-mode Network Service (CONS) by packet mode terminal equipment connected to an Integrated Services Digital Network (ISDN) in accordance with the procedures described in Recommendation X.31. This is done by specifying the mapping of the CONS primitives and parameters to and from the elements of the protocols used by two types of packet mode terminal equipment: a) an X.25 DTE (TE2) connected to an R reference point and accessing an ISDN; and b) a packet mode ISDN terminal (TE1) operating the packet layer protocol (PLP) of Recommendation X.25 and connected to an ISDN at either the S or T reference point. The definitions of TE1, TE2 and TA equipment and R, S and T reference points are given in Recommendation I.411. Recommendation X.612 applies to a TE1 or TE2/TA (i.e. an OSI end system) regardless of whether it is a physically separate system or embedded in other equipment such as a PBX. Recommendation X.612 addresses the provision of the CONS using virtual circuits as described in Recommendation X.25. It does not address the use of X.25 permanent virtual circuits (PVCs). The extension of this Recommendation to include the use of X.25 PVCs is for further study. 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).