This Recommendation specifies the signalling protocol for ATM traffic descriptor modification for the Broadband Integrated Services Digital Network (B-ISDN) at the TB reference point or coincident SB and TB reference point (as defined in Recommendation I.413 [i]) by means of the Digital Subscriber Signalling System No. 2 (DSS 2). This Recommendation extends the Peak Cell Rate (PCR) parameters modification capability specified in Recommendation Q.2963.1 to include the modification of the Sustainable Cell Rate (SCR) and the Maximum Burst Size (MBS) parameters.