Notes

Server
- Must support both POST and GET
  - POST:
    - Variables are not processed
    - DNS query is included as the message body
    - Content-Type header indicates media type
  - GET:
    - The variable dns is processed as a DNS query
      - The query is encoded with base64url
- Must be able to process application/dns-message requests
- A successful HTTP response with a 2xx status code is used for any valid DNS response
  - Doesn't matter if the response is NXDOMAIN
- HTTP responses with non-successful HTTP status codes do not contain a reply to the original query
- Must be HTTPS
  - Not HTTP
- Should assign explicit HTTP freshness lifetime
  - Not sure if this one is possible
  - The assigned freshness must be less than or equal to the smallest TTL in the Answer section of the DNS response
  - If there are no responses in the Answer section, the assigned freshness must not be greater than the minimum field from the SOA record
- HTTP/2 is the minimum recommended version of HTTP
Client
- Should include an HTTP Accept request header
  - Indicates type of content client can understand
- Client must be able to process application/dns-message
- DNS ID should be 0
- May use HTTP/2 padding and compression
- Must account for the Age response header field's value when calculating the DNS TTL of a response