Another reason it's nonsensical: when a DNS response is too large to fit in the payload of a UDP datagram, the server sets the TC bit in the response header (a

Another reason it's nonsensical: when a DNS response is too large to fit in the payload of a UDP datagram, the server sets the TC bit in the response header (alongside whatever truncated results it feels like including), notifying the client of the truncation. The client optionally (but SHOULD) falls back to retrying the query over TCP. https://serverfault.com/a/698254 https://serverfault.com/a/698254