 where the VCI value is translated. A VC link is originated or terminated by the assignment or removal of the VCI value. Routing functions of virtual channels are done at the VC switch/cross-connect. 11 routing involves translation of the VCI values of the incoming VCI links into the VCI values of the outgoing VC links. Virtual channel links are concatenated to form a virtual channel connection (VCC). A VCC extends between two VCC end-points or, in the case of point-to-multipoint arrangements, more than two VCC end-points. A VCC end-point is the point where the cell information field is exchanged between the ATM layer and the user of the ATM layer service. At the VC level, VCCs are provided for the purpose of user-user, user-network, or network-network information transfer. Cell sequence integrity is preserved by the ATM layer for cells belonging to the same VCC. 20.8.2 The Virtual Path Level The virtual path (VP) is a generic term for a bundle of virtual channel links; all the links in a bundle have the same endpoints. A VPI identifies a group of VC links, at a given reference point, that share the same VPC. A specific value of VPI is assigned each time a VP is switched in the network. A VP link is a unidirectional capability for the transport Transmission path Figure 20.13 Relationship between VC and VP, and the transmission path. 11 VC cross-connect: A network element which connects VC links. It terminates VPCs and translates VCI values and is directed by management plane function, not by control plane functions. 20.8 B-ISDN/ATM ROUTING AND SWITCHING of ATM cells between two consecutive ATM entities where the VPI value is translated. A VP link is originated or terminated by the assignment or the removal of the VPI value. Routing functions for VPs are performed at a VP switch/cross-connect. This routing involves translation of the VPI values of the incoming VP links into the VPI values of the outgoing VP links. VP links are concatenated to form a VPC. A VPC extends two VPC end-points or, in the case of point-to