Subject: draft-iab-dns-choices-02.txt comments: host names vs domain names

From: wayne <[email-masked]>
Date: Thu, 09 Jun 2005 08:03:03 -0500

In section 3.2, "Add a prefix to the owner name", it uses examples
such as _mail.example.com.

I suspect that there is a large amount of confusion between what a
"host name" is and a "domain name" right here on this list.

The underscore in _mail prefix is used to ensure that the domain name
is not a valid host name.  Most DNS hosting services allow you
to only create subdomains made up of letter-digit-hyphens.  I think
there will be a large educational problem explaining to the general
public why you can create _mail.example.com, but not www_2.example.com
or my_example.com.

So, in order to help this educational process, can someone give a
short paragraph that explains the differences between host names and
domain names, why the allowed characterset is different between the
two and when you should use one or the other?

-wayne

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From: Rob Austein <[email-masked]>
Date: Fri, 10 Jun 2005 12:48:46 -0400

> two and when you should use one or the other?

Really short answer: see RFC 1034 3.5 and RFC 1035 2.3.1.

Slightly longer answer: Hostnames are a proper subset of DNS names.
Hostnames have to fit the syntax defined in RFC 952 as amended by RFC
1123; DNS names only have to fit the much looser syntax defined in RFC
1035.  You have to use hostnames when you're dealing with applications
that say they're dealing with hostnames or which have their own syntax
definitions which work out to be equivilent to the hostname syntax.
Since most registries will not accept DNS names that don't comply with
the hostname syntax, as a practical matter use of DNS names which are
not hostnames is for the most part restricted to applications like the
_prefix hack.  Note that IDN deliberately encodes to DNS names which
do fit the hostname syntax.

As to "why?"...see the archives of the IDN WG for more details than
you ever wanted, but I won't attempt to summarize because the
opinion/fact ratio in this space is way too high.

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From: wayne <[email-masked]>
Date: Fri, 10 Jun 2005 17:39:10 -0500

In <[email-masked]> Rob Austein <[email-masked]> writes:

> Slightly longer answer: [...]

Thanks for the description.  I understood it and it matches my
understanding of the difference between a hostname and a domain name,
but suspect that it would go right over the head of 99.9% of all
domain owners.  Heck, I suspect that it too many folks that run DNS
hosting services wouldn't immediately understand it without reading
the RFCs and such.

My point remains that one problem with _prefix tricks is that many
people can't create them due to software that restricts domain names
to hostname characters.  But, maybe I'm wrong.  If you think so, let
me know.

I think that dns-choices should mention this problem.

-wayne

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From: Edward Lewis <[email-masked]>
Date: Mon, 13 Jun 2005 08:56:21 -0400

>hosting services wouldn't immediately understand it without reading

In 1998 I taught Intro to Networking and had a student that already 
owned his own successful hosting service.  At the end of the class he 
thanked me saying that he didn't expect to learn anything but instead 
now understood what all the "knobs" were for - like what an MTU was, 
etc.

It's always going to be that way.  There are a lot of service 
providers that don't fully comprehend the technology they use.  How 
many cab drivers could assemble a carburetor blindfolded?  (Even if 
no car built recently has one?)

This is one of the eternal problems.  There will always be someone 
who thinks there is a simple solution who has only an incomplete 
understanding of the technology.  This tests the patience of both 
those who do have a complete understanding of the technology and an 
incomplete understanding of the problem space and those for whom the 
vice versa is true.

>I think that dns-choices should mention this problem.

I agree with this.  The issue in many cases is that "X is not a 
problem for DNS because DNS software is cool" and "X is a problem for 
the users [app writers] of DNS because the software surrounding the 
DNS is a problem."

-- 
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Edward Lewis                                                +1-571-434-5468
NeuStar

If you knew what I was thinking, you'd understand what I was saying.

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From: Patrik Fältström <[email-masked]>
Date: Mon, 13 Jun 2005 20:40:33 +0200

On Jun 13, 2005, at 14:56, Edward Lewis wrote:

> problem for DNS because DNS software is cool" and "X is a problem  
> for the users [app writers] of DNS because the software surrounding  
> the DNS is a problem."

Ack. I will add this.

    paf

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From: "Anders Rundgren" <[email-masked]>
Date: Mon, 13 Jun 2005 22:23:03 +0200

>> people can't create them due to software that restricts domain names

This problem is a bit exaggerated.  Using a simple conversion scheme I managed
to convert any URI into a valid host (prefix) including dividing it in 63-byte chunks.

By doing that I got URI-space of unique DNS data types and I did not
have to tell IANA either!   Who BTW, refused me some RRs as there
was no RFC.

Anders

----- Original Message -----
From: "Patrik Fältström" <[email-masked]>
To: "Edward Lewis" <[email-masked]>
Cc: "IETF DNSEXT WG" <[email-masked]>; "wayne" <[email-masked]>
Sent: Monday, June 13, 2005 20:40
Subject: Re: draft-iab-dns-choices-02.txt comments: host names vs domain names

Ack. I will add this.

    paf

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From: wayne <[email-masked]>
Date: Mon, 13 Jun 2005 15:48:36 -0500

> have to tell IANA either!   Who BTW, refused me some RRs as there

The problem isn't as much in the applications as in things like DNS
hosters.  For example, GoDaddy (which recently passed NSI to become
the largest registrar) does not allow me to create a TXT record with
the name of _underscore_test.unified-spf.org.  The inclusion of the
underscore causes the webform to reject it.  They also don't allow the
creation of SRV records, let alone unknown types.

-wayne

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From: Alex Bligh <[email-masked]>
Date: Tue, 14 Jun 2005 09:48:23 +0100

> creation of SRV records, let alone unknown types.

Isn't this argument a bit backwards? IE don't these DNS hosting services
prohibit use of underscores precisely because there is no standards-based
protocol that mandates their use (and banning them for A records etc.
eliminates a lot of tech support calls from the clue deprived). Neither do
they support RR Types which have no standards-based definition.

If you design the protocol right, vendors (software and hardware) will
support it.

Case in point: most of these DNS vendors previously did not support SRV &
NAPTR records. I am betting, now these are becoming more useful, you will
see a roll-out (clearly they are already in Bind, and will over time get
into hosted DNS products). Should these have been implemented by TXT too,
because n years ago no vendors supported them?

Alex

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From: wayne <[email-masked]>
Date: Wed, 15 Jun 2005 10:43:39 -0500

> If you design the protocol right, vendors (software and hardware) will

Ok, yes, you have a point.  The problem with DNS hosting services only
supporting hostnames and not domainnames will be solved if there is
ever a compelling enough reason for them to accept the customer
support headaches and customer education that they will have to do.

Once DNS hosting services update their software, future _prefix
schemes won't have to blaze that particular path.  They will still
have to educate the general public though about their protocol's usage
of _prefix.

> because n years ago no vendors supported them?

I think that the deployment of both the SRV and NAPTR records would
have happened faster if they were based on the TXT## RR clone idea.
Last year I think IETF-59, the subject of SRV record usage came up in
conjunction with MARID.  The Jabber folks were queried about their use
of SRV records and they reported that there are still lots of
deployment problems with them.  SRV records may be used a lot in
intranets because a single company/organization controls all the
parts, but for an internet-wide protocol like Jabber is still running
into problems.

Of course, I we could probably easily start a flame war just by asking
"should NAPTR records have been done?" instead of why kind of records
they should use.

-wayne