Which technology is used as the basis for the cisco sd-access data plane?

IPsec provides secure communication but is not the primary data plane encapsulation technology for the SD-Access fabric itself.

LISP (Location/ID Separation Protocol) is used as the control plane technology in SD-Access for endpoint and network element mapping, not for the data plane encapsulation.

VXLAN (Virtual Extensible LAN) is the underlying data plane encapsulation technology used in Cisco SD-Access to create the overlay network, providing Layer 2 and Layer 3 virtualization by transporting user traffic across the physical IP-based underlay infrastructure.

802.1Q is a standard for VLAN tagging used for Layer 2 network segmentation, but it is not the overlay data plane encapsulation technology for SD-Access.