Subject: RE: Guidance needed on well known ports

From: "Hallam-Baker, Phillip" <[email-masked]>
Date: Sun, 19 Mar 2006 12:34:36 -0800

> From: Joe Touch [mailto:[email-masked]] 

> And with what port would I reach this magical DNS that would 
> provide the SRV record for the DNS itself?

You use fixed ports for the bootstrap process and only for the bootstrap
process.

> > Fixed ports do not work behind NAT. Anyone who wants to deploy IPv6 
> > would be well advised to pay careful attention to that restriction. 
> > SRV ports work just fine behind a NAT.
> 
> Except that many NATs also intercept DNS requests and 
> redirect them to their own servers, for their own purposes, 
> which can interfere with SRV records (by design).

People who do this are rarely trying to break things. T

> The only thing that works fine behind a NAT is what the NAT 
> vendor wants to work fine. Everything else is up for grabs.

The NAT vendors would like their systems to work as well as possible. If
there had been less hostility to the idea and less determination to ensure
IPv4 actually broke thus forcing deployment of IPv6 this could have worked.
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From: Joe Touch <[email-masked]>
Date: Sun, 19 Mar 2006 21:01:32 -0800

> You use fixed ports for the bootstrap process and only for the bootstrap

Which means that the DNS port needs to be well-known or fixed in advance.

Some other issues to be considered:

	- this change would make the DNS required for proper Internet
	operation, whereas it is currently optional (i.e., only for
	finding the IP address).]

	- hosts may run services but not have control over their own
	DNS entry (or SRV records)

	- firewalling based on ports would no longer be useful
	(one could argue it should not be, but that's a different issue)

> People who do this are rarely trying to break things.

They don't *try* to break things, but then tend to. ;-)

As to 'by design', they're not so much trying to break as to 'help'
(usually for their own purposes).

Joe