TLD Survey: Risks
Closed to TCP Queries
- If UDP response is truncated in the “Answer” section, RFC 1123 section 6.1.3.2 & RFC 2181 section 9 say that it should be retried with TCP
- RFC 2181 makes it clear that “should” in this context means that it is required as a fundamental part of the specification
- RFC 1123 also says that DNS servers MUST support UDP and SHOULD support TCP
- Again “SHOULD” in this case effectively means “must”