| 0 | mandatory | Mandatory keys in this RR | IETF | [RFC9460, Section 8] | 
          
            | 1 | alpn | Additional supported protocols | IETF | [RFC9460, Section 7.1] | 
          
            | 2 | no-default-alpn | No support for default protocol | IETF | [RFC9460, Section 7.1] | 
          
            | 3 | port | Port for alternative endpoint | IETF | [RFC9460, Section 7.2] | 
          
            | 4 | ipv4hint | IPv4 address hints | IETF | [RFC9460, Section 7.3] | 
          
            | 5 | ech | TLS Encrypted ClientHello Config | IETF | [RFC-ietf-tls-svcb-ech-08] | 
          
            | 6 | ipv6hint | IPv6 address hints | IETF | [RFC9460, Section 7.3] | 
          
            | 7 | dohpath | DNS over HTTPS path template | IETF | [RFC9461] | 
          
            | 8 | ohttp | Denotes that a service operates an Oblivious HTTP target | IETF | [RFC9540, Section 4] | 
          
            | 9 | tls-supported-groups | Supported groups in TLS | IETF | [draft-ietf-tls-key-share-prediction-01, Section 3.1] | 
          
            | 10 | docpath | DNS over CoAP resource path | IETF | [RFC-ietf-core-dns-over-coap-19, Section 3] | 
          
            | 11-65279 | Unassigned |  |  |  | 
          
            | 65280-65534 | N/A | Reserved for Private Use | IETF | [RFC9460] | 
          
            | 65535 | N/A | Reserved ("Invalid key") | IETF | [RFC9460] |