About named...(bind)

[phn at icke-reklam.ipsec.nu]

CosmicD <cosmicmania at hotmail.com> wrote:
> Hello,

> I'd like to ask if there isn't any human text that explains very well what
> IN A means or PTR, i'm running my own server for 2 week now, but i would
> like to take the aspect of running my own dns server for my account too,

> manuals tend to behave as if you know what they'r talking about but there is
> so much that doesn't have structure in my mind just yet

> what are these 2 in-arpa files ( i know that it's some kind of herritage
> from the original arpanet, but what do these files *DO*)

> What do I do to prevent ppl from kicking me from irc because I actually put
> "core.example.com" as my primary servername (but it keeps saying
> www.excample.com when I join irc, so i get killed all the time with my
> server:) (just how does this work actually)

> thx

> cd

There is a number of examples on "the net", i'll only suggest one :
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/dns.html

Beyond that the book "Managing DNS and BIND" by cricket liu ( 4.th ed) is the
"standard work".

Said that, a very short description :


DNS aka Domain Name System is a distributed database arranged in a 
hierarchy.  The top in denoted "root" and is known via a file that
is supplied to all nameservers.

Each level in this hierarchy may "delegate" a portion below. So the root
delegated "com" "net" "se" and a few hundred other domains.

The folks running one of these controls what is commonly called a TLD
( or top level domain). They also delegate, and many does this for a fee (thats
what they live on). Suppose you apply for "CosmicD.com" .Then you are
supposed to set up a couple of nameservers that knows everything (in dns) that
is to know about "CosmicD.com". Then you will have to ask the folks at "com"
to delegate "CosmicD.com" (and everything below that) to your nameservers.
You will typically store the data in a "zonefile" which will (among other
things ) contain 'A' records ( mapping computer names, or Fully Qualified
Names) to ip-addresses.

Anyone else on Internet now has a chain to follow whenever they want to
get data about something at or below "CosmicD.com", they ask the root's, who 
says "ask a com server", the comservers in turn will refer to your servers
and your servers will, when asked, supply the answer.

A commonly confused area is the so called "reverse domains" where all 
existing ip-addresses is mapped to computer names. This is made possible
by the fact that ipaddresses conventionally is expressed as 'dotted decimal'.
Since dot's are the delimiting character between domains, it's possible
to arrange this. From root is a "in-addr.arpa" domain, below that digits
from 1 to 226(or so) which happens to be the first octet of an ipaddress.
This is continued, octet by octet until one finds the point where an 
organization has been assigned all addresses ( at least until CIDR delegation
was begun in 1994. You will read about it).

Suppose you have got the "class-C" address 192.1.2.0. arin/ripe or some other entity
will then assign your nameservers to answer for everything below 2.1.192.in-addr.arpa.
You will typically fill this zonefile with PTR records ( mapping ipaddresses
to computer names)


The invention of DNS was one of the most successfull launching of a technology
ever seen. In spite of a growth that was 1000's of times bugger then the 
most aggressive nightmare of the designers of arpanet, it still functions well
and has no problems with future growth. 
This is attributed by a careful design where the number of servers get's
larger as Internet expands, combined with local caching whenever possible.


Now, go and get the book, it's worth the money !



-- 
Peter Håkanson         
        IPSec  Sverige      ( At Gothenburg Riverside )
           Sorry about my e-mail address, but i'm trying to keep spam out,
	   remove "icke-reklam" if you feel for mailing me. Thanx.