Re: Port numbers and IPv6 (was: I-D ACTION:draft-klensin-iana-reg-policy-00.txt)

[David Hopwood <david.nospam.hopwood at blueyonder.co.uk>]

Scott Bradner wrote:
> > > I was surprised that TCP-over-IPv6 and UDP-over-IPv6 didn't increase
> > > the port number space. I know it's off-topic here, but anyone know why
> > > they didn't? It surely must have been considered.
> >
> > That was considered to be part of TCPng, and as best I recall was 
> > explicitly out of scope.
>
> correct

I was looking more for an explanation of how and why it was decided to
be out of scope.

The arguments for considering it to be in scope would have been:

 - the TCP and UDP "pseudo-headers" needed to be changed anyway to
   accomodate IPv6 addresses (see section 8.1 of RFC 2460);

 - the pressure on well-known port numbers was obvious at the time;

 - supporting 32-bit port numbers in IPv6 stacks could have been done
   at very little incremental cost;

 - a larger port space would have been an additional incentive to
   adopt IPv6;

 - more ambitious changes to TCP would have a low probability of
   adoption within a relevant timeframe;

 - it makes sense for the port number space to be the same size for
   UDP-over-IPv6 and TCP-over-IPv6.


Jeroen Massar wrote:
> It would not make much sense, between 2 hosts you can already have
> 65536*65536 possible connections*, which should be more than
> enough(tm) ;)

Not for connections to a well-known port.

--
David Hopwood <david.nospam.hopwood at blueyonder.co.uk>


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