This feature is supported on VPLS and VLL services where the end-to-end solution is built using two node solutions (requiring SDP connections between the nodes).
In VLAN swapping, only the VLAN ID value is copied to the inner VLAN position. The Ethertype of the inner tag is preserved and all consecutive nodes work with that value. Similarly, the dot1p bits value of outer tag is not preserved.
Figure: Ingress VLAN swapping shows a network where, at user-access side (DSLAM-facing SAPs), every subscriber is represented by several QinQ SAPs with inner-tag encoding service and outer tag encoding subscriber (DSL line). At the aggregation side (BRAS- or PE-facing SAPs) every subscriber is represented by DSL line number (inner VLAN tag) and DSLAM (outer VLAN tag). The effective operation on the VLAN tag is to drop the inner tag at the access side and push another tag at the aggregation side.
