 a signaling VCC to establish or release a VCC within a preestablished VPC between two UNIs. 20.9.2 Signaling Virtual Channels 20.9.2.1 Requirements for Signaling Virtual Channels. For a point-to-point sig- naling configuration, the requirements for signaling virtual channels are as follows: One virtual channel connection in each direction is allocated to each signaling entity. The same VPI/VCI value is used in both directions. A standardized VCI value is used for point-to-point signaling virtual channel (SVC). In general, a signaling entity can control, by means of associated point-to-point SVCs, user-VCs belonging to any of the VPs terminated in the same network element. As a network option, the user-VCs controlled by a signaling entity can be con- strained such that each controlled user-VC is in either upstream or downstream VPs containing the point-to-point SVCs of the signaling entity. For point-to-multipoint signaling configurations, the requirements for signaling virtual channels are as follows: Point-to-Point Signaling Virtual Channels. For point-to-point signaling, one virtual channel connection in each direction is allocated to each signaling entity. The same VPI/VCI value is used in both directions. General Broadcast Signaling Virtual Channel. The general broadcast signaling vir- tual channel (GBSVC) may be used for call offering in all cases. In cases where the "point" does not implement service profiles or where "the multipoints" do not sup- port service profile identification, the GBSVC is used for call offering. The specific VCI value for general broadcast signaling is reserved per VP at the UNI. Only when meta-signaling is used in a VP is the GBSVC activated in the VP. Selective Broadcast Signaling Virtual Channels. Instead of the GBSVC, a virtual channel connection for selective broadcast signaling (SBS) can be used for call offering, in cases where a specific service profile is used. No other uses for SBSVCs are foreseen. 20.10 QUALITY OF SERVICE (QOS) 20.10 QUALITY OF SERVICE (QOS) 20.10.1 ATM 