Subject: Re: Guidance needed on well known ports

From: [email-masked] (Noel Chiappa)
Date: Fri, 24 Mar 2006 07:23:30 -0500 (EST)

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

    >> Noel Chiappa wrote:

    >>> From: Keith Moore <[email-masked]>

    >>> Regarding SRV, it's not acceptable to expect that as a condition of
    >>> deploying a new application, every user who wishes to run that
    >>> application be able to write to a DNS zone. Most users do not have
    >>> DNS zones that they can write to.

    >> Yes. Architecturally speaking, it's somewhat dubious that information
    >> which really only needs to be localized to the host
    >> (application<->port binding) has to be sent to the DNS.

    >> It would be easy to run a tiny little U[D]P "binding" server that
    >> took in an application name (yes, we'd have to register those, but
    >> string-space is infinite), and returned the port.

    > Only if it asked a well-known server ON THAT MACHINE.

Yes, but why is that a problem? Again, in architectural terms, you are
limiting the scope over which the information (about which appplication is
on which port) has to be spread, to the machine it applies to - always good
when you get that kind of congruence.

Why would you want machine X to know the mapping for machine Y? If you're
going to be talking to machine Y anyway (to talk to the application), why
can't Y also be the one you ask for the mapping? And then you don't have to
set up all the mechanism for machine X to learn what machine Y's mappings
are.

    > But we cannot assume a hosts' DNS is available for that purpose. For
    > most of us, the DNS entry isn't under our control, nor is it likely to
    > be for the forseeable future.

Keith and I concurred on that.

	Noel

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From: "Spencer Dawkins" <[email-masked]>
Date: Fri, 24 Mar 2006 06:31:43 -0600

Ack on Noel's other points, but this is worth mentioning...

> Keith and I concurred on that.

I have learned not to tell people (especially Keith and Noel) that DNS is 
the right answer to all questions, but it is significantly difficult having 
most of the machines on the net impossible to locate from most of the other 
machines on the net.

We have "solved" this problem in the past with a heavy reliance on 
client-server protocols and SIPpish proxies, which are possible to locate 
from most of the other machines on the net.

I appreciate very much EKR's talk on distributed hash tables at the plenary 
last night. I don't know if this is the right direction, but the problems 
DHTs are intended to solve would be useful to solve.

And it would be good if we worked on DHTs AND other possible solutions, 
instead of arguing about whether DHTs are the right answer and not working 
on anything else, either!

Thanks,

Spencer

---

From: Joe Touch <[email-masked]>
Date: Fri, 24 Mar 2006 07:32:33 -0800

>     >>> From: Keith Moore <[email-masked]>
...
> when you get that kind of congruence.

It isn't a problem, but it isn't DNS if you do it that way - that was my
only observation.

Joe