Re: [Uta] Port 465

["Christian Huitema" <[e-mail]>]

On  Sunday, March 9, 2014 11:52 PM, Eliot Lear wrote

> On 3/8/14, 8:33 PM, Christian Huitema wrote:
>> The port collision is only a practical problem if the same server wants
to
>> deploy both Secure SMTP submission and the experimental "URL Rendesvous
>> (sic) Directory for SSM."
>
> Routers running URD intercept all packets using port 465, regardless of
> destination.

That particularity of the URD design seems to be the root of the problem. It
assumes that port numbers have global meaning, when the practice has always
been that port numbers are locally assigned by host systems. Yes, there is
an IANA registry, but its practical use is advisory, a convenience, not a
hard coded rule of the Internet. I suppose that the IAB could have an
interesting debate on this subject.

The net result is that URD is hard to deploy, because ISP will presumably be
reluctant to break secure mail traffic and receive the corresponding amount
of support calls. If I was responsible for that product, I would explore
design changes that minimize the issue. For example, using some form of IP
anycast address, so the routers only have to intercept the packets that are
meant to be intercepted. Or maybe put some kind of signature in the packet,
like a TCP option that asks to "intercept me." Or a specific source port.
There has to be a way to minimize the problem...

-- Christian Huitema