The user enables the use by an LDP session of the Downstream-on-Demand (DoD) label distribution using the command config>router>ldp>peer-parameters>peer> dod-label-distribution.
When this option is enabled, LDP will set the A-bit in the Label Initialization message, when the LDP session to the peer is established. When both peers set the A-bit, both uses the DoD label distribution method over the LDP session [rfc5036].
This feature can only be enabled on a link level LDP session and applies to prefix labels only, and not service labels.