XFR

XFR (Zone Transfer): refers to the mechanism by which DNS zone data is transferred between authoritative name servers to ensure consistency and availability. The two primary forms are AXFR, which performs a full transfer of the entire zone, and IXFR, which transfers only incremental changes since the last update. XFR is fundamental to authoritative DNS operations, enabling synchronization between primary and secondary servers, supporting redundancy, resilience, and geographic distribution. Because zone transfers expose authoritative data, XFR operations are typically restricted and secured using access controls, authentication, and, in modern deployments, encrypted transport.