Need for FQDN?

Hello...

Could someone explain to me the need, or point of having a FQDN (fully
qualified domain name). I attempted a test post earlier without one and
it seems to have worked. My newsgroup provider claims to offer a FQDN
though and I wasn't sure if I needed to take them up on it.

If you could comment whether it is useful/needed for email too that
would be nice. When I send someone an email now the message ID is
suffixed "@matt-laptop" (after the string of numbers and letters), which
is the output of `hostname --fqdn` on my system. It doesn't seem to
cause any problem.

Sorry, I guess I'm just not clear on the concept. I'm just your typical
joe-twelve-pack, not running any servers or anything, but want to be a
good netizen.
Thanks...
--
Matt

Matt <(E-Mail Removed)> writes:

> On 2009-09-14, Chris Davies <chris-(E-Mail Removed)> wrote:
>> Matt <(E-Mail Removed)> wrote:
>>> Could someone explain to me the need, or point of having a FQDN (fully
>>> qualified domain name).
>>
>> A registered FQDN allows us "out here" to differentiate your system from
>> another one with the same simple name.
>>
>> If you and I both call our systems "pc" then how can you differentiate
>> your "pc" from mine? The answer is to qualify the name with a
>> domain. My domain is roaima.co.uk, so the system's FQDN would be
>> pc.roaima.co.uk. No-one else is allowed to have roaima.co.uk - it's
>> globally unique. Your "pc" would be different, and with its FQDN similarly
>> uniquely named.
>
> And by your domain you mean you are the owner/operator of roaima.co.uk?
> As opposed to it being the host name of an ISP to which you and many
> others subscribe? That is one point of confusion for me, if it's
> supposed to be a unique static IP for an individual user, or just any valid
> name even one from an ISP is ok.

It would be a name for an individual computer, not an individual user.

My university owns the domain name nmsu.edu. My department owns
cs.nmsu.edu. Each computer in the department has its own FQDN, and can
be accessed from anywhere in the world using that FQDN -- the machine in
my office is viper.cs.nmsu.edu, and I'm logged into it now while sitting
at home (though that's not the machine I'm posting this from).

I own the pfeifferfamily.net domain name. The machines in my house
belong to the wb.pfeifferfamily.net domain; this domain is only visible
externally when on my VPN. The only DNS server for
wb.pfeifferfamily.net is located in my house (the VPN server is outside
the house, in my department at the university), so the
wb.pfeifferfamily.net domain is only visible when in my house or on my
VPN. So, from my laptop and a handful of other machines, I can log into
my home machines by logging into FQDNs like
snowball.wb.pfeifferfamily.net

You can, however, check the progress of the new back porch we're having
built by going to http://pfeifferfamily.net/, a website that is hosted
by a hosting firm a couple of thousand miles away from me.
--
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
and this we should do freely and generously. (Benjamin Franklin)

On Mon, 14 Sep 2009 18:07:39 -0400, Matt <(E-Mail Removed)> wrote:

> Could someone explain to me the need, or point of having a FQDN (fully
> qualified domain name). I attempted a test post earlier without one and

Some software, such as leafnode, will not run without one. It uses it
to generate messageids, which the rfc's require using a registered
fqdn.

It's easy to register for a free one at a site like http://www.dyndns.com/
If you're using a dynamic ip, many routers include autmatic updating of
the ip address at dyndns.org.

Regards, Dave Hodgins

--
Change nomail.afraid.org to ody.ca to reply by email.
(nomail.afraid.org has been set up specifically for
use in usenet. Feel free to use it yourself.)

Matt <(E-Mail Removed)> wrote:
> And by your domain you mean you are the owner/operator of roaima.co.uk?

Yes. If you look in whois you'll find it's registered to "a private
individual".

If you perform some DNS lookups you'll find a small number of hosts and
services advertised within that domain; for example mail.roaima.co.uk
is my mail server running at home. Internally I have a larger number
of hosts defined, such as sparrow.roaima.co.uk and eagle.roaima.co.uk;
these names correspond to specific machines on my home network.


> As opposed to it being the host name of an ISP to which you and many
> others subscribe?

My administering my own domain I can make the particular ISP that I use
almost completely irrelevant. (Yes, I know that a rDNS lookup on my IP
address or AS network will let you determine my ISP. So what?) I can
change my ISP independently of my email address or website.


> That is one point of confusion for me, if it's
> supposed to be a unique static IP for an individual user, or just any valid
> name even one from an ISP is ok.

A FQDN is not necessarily directly related to an IP address. One is a
(human readable) name, the other is a (machine orientated) network
address.

You can email me as per the "Reply-to" line in the header of this news
article, but there is no such server as roaima.co.uk. But because I
manage the roaima domain I can guarantee the email address is unique
within that domain. I could equally have decided to make my email address
(E-Mail Removed), and provided I correctly configured the
necessary DNS entries and email services, that would work just as well.


> Yes I have a good sense of what's a valid email address. I'm fairly new
> to linux however and was concerned there was some under the hood
> configuration I was supposed to take care of.

No... as long as you "own" that email address and know how to send email
via your ISP with that address in the message you should be fine.


> I know it must seem like
> an odd question... here's a website I was looking at that suggested
> users obtain a FQDN from a vendor just for posting news:

> http://www.andrews-corner.org/slrn.html

Domain names are cheap (I can buy UK domains for well under £10/year;
approximately USD$15/year), and they help to insulate oneself from a
specific ISP or other big organisation. In your case, you're now tied
to yahoo. If you get fed up with them you have to change your email
address. Maybe that wouldn't matter to you but it would frustrate me.

Chris

In comp.os.linux.networking on Mon, 14 Sep 2009 22:07:39 +0000 (UTC),
Matt <(E-Mail Removed)> wrote:

> Hello...
>
> Could someone explain to me the need, or point of having a FQDN (fully
> qualified domain name).

The big advantage to using a FQDN for Usenet in your Message-IDs is
that it helps you to find replies to your posts.

In my slrn scorefile I have:
[*]
Score: 1000
References: pjr@pjr\.gotdns\.org> *$

Which selects all direct replies to my posts.

This kind of filtering won't work if you have something generic like
your "@news.albasani.net" in your Message-IDs.

> I attempted a test post earlier without one and
> it seems to have worked.

Yes: news.albasani.net is generating the Message-ID for you.

> My newsgroup provider claims to offer a FQDN
> though and I wasn't sure if I needed to take them up on it.

It's worth doing. You'll then want to add
set generate_message_id 1
posting_host <your FQDN>
in your .slrnrc file.

> If you could comment whether it is useful/needed for email too that
> would be nice. When I send someone an email now the message ID is
> suffixed "@matt-laptop" (after the string of numbers and letters), which
> is the output of `hostname --fqdn` on my system. It doesn't seem to
> cause any problem.

You don't need a FQDN for email. In fact, it would be unwise to use a
"borrowed" FQDN (such as one provided by albasani.net) except for the
specific purpose for which it was "lent".

> Sorry, I guess I'm just not clear on the concept. I'm just your typical
> joe-twelve-pack, not running any servers or anything, but want to be a
> good netizen.

Basically, an FQDN can be a useful thing to have, but you don't need
it for "typical" purposes.

--
PJR :-)
slrn newsreader v0.9.9p1: http://slrn.sourceforge.net/
extra slrn documentation: http://slrn-doc.sourceforge.net/
newsgroup name validator: http://pjr.gotdns.org/usenet/validator

I've not split a hair all day so will ask - isn't there a trailing dot
in a "real" FQDN? Ie foo.bar.baz. rather than foo.bar.baz?

rick jones
--
Process shall set you free from the need for rational thought.
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

On Tue, 15 Sep 2009 17:12:58 +0000 (UTC), Rick Jones wrote:
> I've not split a hair all day so will ask - isn't there a trailing dot
> in a "real" FQDN? Ie foo.bar.baz. rather than foo.bar.baz?

Short answer no trailing dot.
Long answer http://www.ietf.org/rfc/rfc1035.txt :-D

Bit Twister <(E-Mail Removed)> wrote:
> On Tue, 15 Sep 2009 17:12:58 +0000 (UTC), Rick Jones wrote:
> > I've not split a hair all day so will ask - isn't there a trailing dot
> > in a "real" FQDN? Ie foo.bar.baz. rather than foo.bar.baz?

> Short answer no trailing dot.
> Long answer http://www.ietf.org/rfc/rfc1035.txt :-D

That got me curious and searching, which led me to:

http://www.dns-sd.org/TrailingDotsInDomainNames.html

which then pointed at:

http://www.ietf.org/rfc/rfc1034.txt which says:

When a user needs to type a domain name, the length of each label is
omitted and the labels are separated by dots ("."). Since a complete
domain name ends with the root label, this leads to a printed form
which ends in a dot. We use this property to distinguish between:

- a character string which represents a complete domain name
(often called "absolute"). For example, "poneria.ISI.EDU."

- a character string that represents the starting labels of a
domain name which is incomplete, and should be completed by
local software using knowledge of the local domain (often
called "relative"). For example, "poneria" used in the
ISI.EDU domain.

Relative names are either taken relative to a well known origin, or
to a list of domains used as a search list. Relative names appear
mostly at the user interface, where their interpretation varies from
implementation to implementation, and in master files, where they are
relative to a single origin domain name. The most common
interpretation uses the root "." as either the single origin or as
one of the members of the search list, so a multi-label relative name
is often one where the trailing dot has been omitted to save typing.

rick jones
--
the road to hell is paved with business decisions...
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

On 2009-09-15, Chris Davies <chris-(E-Mail Removed)> wrote:

> Domain names are cheap (I can buy UK domains for well under £10/year;
> approximately USD$15/year), and they help to insulate oneself from a
> specific ISP or other big organisation. In your case, you're now tied
> to yahoo. If you get fed up with them you have to change your email
> address. Maybe that wouldn't matter to you but it would frustrate me.

Yes, but it is just a throwaway address; I don't use it for regular
correspondence. Yahoo's pretty lame anyway. :-)

I take it you have to do spam filtering yourself?

--
Matt

On 2009-09-15, Joe Pfeiffer <(E-Mail Removed)> wrote:

> I own the pfeifferfamily.net domain name. The machines in my house
> belong to the wb.pfeifferfamily.net domain; this domain is only visible
> externally when on my VPN. The only DNS server for
> wb.pfeifferfamily.net is located in my house (the VPN server is outside
> the house, in my department at the university), so the
> wb.pfeifferfamily.net domain is only visible when in my house or on my
> VPN. So, from my laptop and a handful of other machines, I can log into
> my home machines by logging into FQDNs like
> snowball.wb.pfeifferfamily.net

Does the DNS server simply run from a desktop or require special
hardware?

> You can, however, check the progress of the new back porch we're having
> built by going to http://pfeifferfamily.net/, a website that is hosted
> by a hosting firm a couple of thousand miles away from me.

Gave me a 404! But the search function works. I like that the mess of
construction doesn't stop you from grilling. :-)

--
Matt