====== Tags ======

Here is a non-exhaustive list of known tags:

^ High word            ^ Low word             ^ Name in English       ^ Validity          ^ Description                                                                   ^ Value structure             ^
| ffff-ffff-ffff-ffff  | 0000-0000-0000-0000  | placeholder           | anywhere          | used for examples and testing                                                 | unspecified                 |
| edcc-1a0a-8817-f0f6  | 4711-bbca-83f3-6f5d  | self-proposed name    | anywhere          | name given by a zone/service to itself                                        | localised text              |
| :::                  | 0d0b-c1d2-fe54-36e8  | edge pointer          | metadata service  | endorses another zone and gives it a name                                     | //TODO//                    |
| :::                  | 0b40-40b1-1f4a-ded4  | authoritative source  | metadata service  | other tags in this record indicate where to find a complete copy of the zone  | empty                       |
| :::                  | ba58-942b-c175-b313  | maintainer info       | metadata service  | name/contact details for zone owner                                           | localised text              |
| :::                  | 9310-2a53-98f4-a870  | cache duration        | metadata service  | maximum number of seconds for which the zone may be cached                    | u16                         |
| :::                  | e8ed-44a7-a476-0a51  | surrogate hostname    | anywhere          | DNS-style hostname to use in protocols that require one                       | string                      |
| 849f-4d8f-a556-6e1e  | df4e-0109-3265-d87b  | IPv4                  | anywhere          | IPv4 address                                                                  | [4]u8                       |
| :::                  | 527f-0be4-8e93-a502  | IPv6                  | :::               | IPv6 address                                                                  | [16]u8                      |
| :::                  | 77e3-4e50-6dab-3c1e  | TCP                   | :::               | TCP port number                                                               | u16                         |
| :::                  | b231-d968-259f-5edf  | UDP                   | :::               | UDP port number                                                               | u16                         |
| :::                  | 7bd4-b12b-7ba9-f2fc  | QUIC                  | :::               | QUIC port number                                                              | u16                         |
| :::                  | 0987-da54-8679-e3fe  | TLS                   | :::               | TLS certificate hash(?)                                                       | //TODO//                    |
| :::                  | 02bc-6f4b-ac77-1630  | IMAP                  | :::               | //TODO//                                                                      | //TODO//                    |
| :::                  | 6971-6c69-d21d-64fb  | SMTP                  | :::               | //TODO//                                                                      | //TODO//                    |
| :::                  | 9082-761f-c79d-433f  | POP                   | :::               | //TODO//                                                                      | //TODO//                    |
| :::                  | 7dcc-0481-3e5d-891c  | DNS                   | :::               | //TODO//                                                                      | //TODO//                    |
| :::                  | fccd-66df-c927-9ac4  | HTTP                  | :::               | HTTP base path                                                                | string starting with ''/''  |
| :::                  | 12b7-ba1f-4cba-a18a  | Gemini                | :::               | Gemini base path                                                              | :::                         |
| :::                  | 59e9-725e-59de-27d6  | Gopher                | :::               | Gopher base path                                                              | :::                         |

pawsd-fennel has [[https://codeberg.org/winter/pawsd-fennel/raw/branch/main/dictionary|a more easily machine-readable version of the first two columns]].

Within values, there are a few common constructs:
  * **localised text**: language code length (u8), ISO-639 language code ([_]u8), raw UTF-8 string (no length prefix or terminator)
  * **string**: raw UTF-8 string (no length prefix or terminator)

Note that strings don't need any indication of their length, because this is already given by the structure of the record itself, which includes a "value length" field.