https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/xe-3s/qos-plcshp-xe-3s-book/qos-plcshp-class-plc.html

Section: Advanced Addressing and Routing Solutions
Explanation/Reference:

The ORF filter should be applied so the route reflector or upstream peer suppresses the unwanted Branch A prefix before sending updates toward the resource-constrained branch. Cisco BGP outbound route filtering lets a receiving router advertise a prefix-list filter to its peer, causing that peer to apply the filter outbound.
This is useful when a router has limited CPU or memory because unwanted prefixes are never sent across the session. In the described design, HQ must prevent Branch A prefixes from reaching R4, while Branch B has limited resources. The answer using the 10.10.10.0/24 prefix list on R2 aligns with filtering the Branch A prefix at the point where HQ can control route reflection or advertisement toward the constrained branch path.
Applying the filter on the wrong router or using the wrong prefix would still allow unnecessary updates. ORF is preferred over simple inbound filtering when the goal is to reduce received route volume. Reference topics:
BGP ORF, prefix-list signaling, route-reflector filtering, branch route scale, outbound update suppression.

Cisco SD-Access uses LISP as the control plane protocol to map endpoint identifiers to routing locators. This allows the fabric to track endpoint location and support scalable, policy-based forwarding across the SD-Access overlay.