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Re: Purpose of Port 0.

2017-02-20 16:50:11
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

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