Virtual Circuits and Virtual Paths
ATM is connection-oriented
The basic abstraction of ATM is the Virtual Channel (VC)
- which can be unidirectional and
- whose id only has local significance
A VC is contained within a Virtual Path (VP)
- which is a bi-directional point-to-point connection between two ATM switching points and
- only has local significance
Each VC link is identified by its VC identifier (VCI) included in the ATM cell header
Each VP link can contain a number of VCs and is identified by its VP identifier (VPI) also included in the ATM cell header
A VC Connection (VCC) is a sequence of VC links connected at ATM switches
An ATM switch can switch VCs or entire VPs