VPI/VCI and label stacking
Is VPI/VCI hierarchy equivalent to label stacking?
In label stacking, unless a label is being pushed or popped only one label identifies the labeled channel.
In ATM, a virtual channel is identified by the combination of the VPI and VCI.
In ATM, terminating a VPC is equivalent to VCC switching to a GSMP switch.
Thus VPC switching and VCC switching are both treated as switching on a single single label.
Add Branch (16) and VPC Add Branch (26) are retained.
All non-ATM branches use Add Branch (16)