DNS Flag Days serve notices to obsolete Domain Name System (DNS) servers that existing accommodations to provide them with compatibility for pre-1999 standards will be phased out.
The Flag Days attempt to:
- Speed up DNS
- Improve DNS reliability
- Improve DNS security
In 1999, DNS was extended with eDNS(0), yet servers incompatible with eDNS(0) continue to be used today. To improve the performance of the internet, the 2019 DNS flag day temporarily ceased to support those legacy DNS servers.
The 2020 Flag Day will tackle the maximum DNS message size to bring them down under 1232 bytes. This will stop DNS message fragmentation and improve both the reliability and security of DNS.