Which technique can be used to have media flow directly between two endpoints that have a NAT between them?

No Cisco router API exists that allows endpoints to temporarily disable NAT; NAT traversal requires protocol-level solutions, not administrative disablement.

Cisco Mobile and Remote Access (MRA) routes media through Expressway infrastructure for remote endpoints - it does not create a direct media path between two internal endpoints.

There is no Cisco protocol called 'Cisco access protocol' that creates direct paths between internal endpoints; this is a fabricated option.

STUN (Session Traversal Utilities for NAT) works by allowing an endpoint to send a binding request to a STUN server on the public internet, which reflects back the public IP address and port that the NAT device assigned. Both endpoints can exchange these mapped addresses via signaling, enabling direct UDP media flow through the NAT without requiring NAT reconfiguration.