Hi, Brian, On 2/20/2017 11:34 AM, Brian E Carpenter wrote: > On 21/02/2017 01:33, John C Klensin wrote: >> ... >>> Well UDP source port 0 means don't reply (RFC 768). It's for >>> uni directional streams. >>> >>> As for 0 to select a ephemeral port that is a BSD sockets >>> convention. That isn't something the IETF should specify. >> While _assignment_ of a por is an IETF matter and I mostly agree >> with Mark, recognition of how one is being used is is a little >> different. >> >> It seems to me that this is rather more an IANA registry matter >> than a standardization one > Not quite though. Noting the RFC 768 usage as a source port, aren't > all these uses equivalent to saying 'Not valid on the wire as a > destination port'? I don't think so. 768 says that if you receive 0 as source, do not reply. That doesn't mean you can't *initiate* to port 0, if it is ever assigned. Joe