An attempt to understand the pieces of EDNS0 and the changes necessary to have Twisted Names support it:

• EDNS0
  • OPT record
    • Explicit OPT record class/type
      • Teach cache about it - MUST NOT BE CACHED
      • Teach recursive resolver about it - MUST NOT BE FORWARDED
      • Teach loaders about - MUST NOT BE LOADED FROM MASTER FILE
    • Extended label ("0" "1" type) parsing (REJECTED BY 2671bis)
    • Maximum UDP datagram size field
    • Arbitrary extension support (attribute/value pairs in RDATA section)
  • Extended Message object with additional EDNS0 items
    • Subclass of Message?
    • maxSize (Message has it already, can we re-use it?)
    • Extended RCODE - partly defined by RCODE field in OPT record
  • Accept max UDP size as configuration? determine it from system automatically?
    • Server and client need this
  • Client
    • Automatically send EDNS0 queries
    • Fall back to DNS queries when detecting server does not support EDNS0?
  • Server
    • Send EDNS0 responses to EDNS0 queries
    • (Do not send EDNS0 responses to DNS queries)
• DNSSEC
  • ??????