N-GEN Communications Web-based Seminars ©NGCS

Seminar - An Overview of Communications Technologies

Module 4 - ATM Technology                                                                                              Slide 14 of 46 _________________                                                                                  __________

                                 ATM Network Building Blocks - Virtual Circuits

                                            Virtual Circuit (VC)

                                            Virtual Path (VP)

                                            Permanent Virtual Circuit (PVC)

                                            Switched Virtual Circuit (SVC)

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VC and VP make up the transmission portion of the ATM layer. The ATM layer provides the transmission and switching functions. The transmission portion provides call transfer information and is part of the ATM cell header. PVC and SVC are the end user connections.

Virtual Circuit (VC) - is the unidirectional virtual channel transmission of cells from a specific user. It is mapped to a virtual path and transmission path. VCs are linked together to form virtual channel connections to provide point-to-point or multipoint connections across the ATM network.

Virtual Path (VP) - is a bundle of virtual circuits with the same user end points. VPs linked with Virtual Path Connections define point-to-point or multipoint connections across the ATM network.

Permanent Virtual Circuit (PVC) - is a permanently established connection for consistent and frequent data transfer. The connection is established in advance.

Switched Virtual Circuit (SVC) - is a switched virtual circuit set up when a call is made.