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An [Acronym] for __D__omain __N__ame __S__ervice.

The glue that binds the InterNet together -- the [Protocol] that takes you from typing <tt>www.JRandomWebsite.com</tt> into your web browser to the InternetProtocol address of the site which would look something like <tt>123.45.67.89</tt> so that:

* You can remember <tt>www.amd.com</tt> instead of <tt>64.41.192.105</tt>
* They can change the name to point somewhere else if they need to (if something like the CodeRedBungle happens).

[DNS] does more than just that (a ForwardLookup) though -- there are different types of ResourceRecord~s. It is usually provided by a program called named(8) -- commonly a version of bind, the Berkeley Internet Name Daemon.

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This is pasted here from a conversation on IRC because this information is important but I don't have time to sit down and write it up as a nice paragraph, it should also have it's facts verified:

<verbatim>
 <Isomer> people set up dns so that replies don't come from the same ip sometimes
 <quantum_> i wonder about this: client c sends a resquest to s1
 <quantum_> which forwards the request to s2
 <quantum_> but using a wierd packet so the reply goes right back to c
 <quantum_> bypassing s1 completely
 <Isomer> that doesn't happen
 <Isomer> it's more when you have a machine
 <Isomer> h1
 <Isomer> with two interfaces i1 and i2
 <quantum_> (which is just stupid, because then s1 cant cache)
 <Isomer> which have one unique IP each
 <Isomer> now the default route goes out i1
 <Isomer> but i2 is the IP in DNS as the nameserver
 <Isomer> you send a query to i2, but when h1 creates a new packet and sends it
 <Isomer> the OS attaches i1 as the source address instead of i2
 <Isomer> because it uses the IP of the interface that the packet leaves from
 <Isomer> see?
 <Isomer> this can't be easily fixed either, coz if you use the IP of i1
 <Isomer> then people on i2 have the same issue
 <Isomer> bind fixes this by opening one port per interface
 <Isomer> hence why you see lots of :53's for bind
 <Isomer> but it can't bind to new port 53's when you bring up another interface after it's started and has  dropped privileges
 <quantum_> ah
 <Isomer> so yeah
 <Isomer> I should wiki this
 <quantum_> yes
 <quantum_> because many things were just made clear
 <Isomer> which is why so many things have cone nat's
 <Isomer> because if they were restrictive nats
 <quantum_> all because recv() can tell you who sent the packet
 <Isomer> then you can't query some dns servers
 <quantum_> but not where it arrived in the machine.
 <Isomer> thats not the problem
 <Isomer> the problem is sending a packet with a specific source address
 <quantum_> im sure ive seen log messages about bind discovering new interfaces
 <quantum_> so they could leave a suid root child which communicates to its parent over unix domain socket
 <quantum_> to pass file descs
 <quantum_> and does nothing else, so is (hopefully) mostly secure
 <Isomer> you run bind as root?
 <quantum_> (maybe they do this, i dont admin any bind nameservers, nor have looked at the source)
</verbatim>

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More crud, from the deleted page about the A6 ResourceRecord:

I tried setting this up at home - debian woody, bind9. I could do host -t A6 $domain fine, and host -t A6 $host.$domain worked too, although it returned the fragment for the host and the domain name as part of the record - not what its supposed to do.  Glibc under debian woody doesn't appear to support it, and its listed as a bug as of June 15 2003, tagged 'wishlist'. Pity too, as A6 addressing makes a LOT of sense for dynamic IP.

I had:

<verbatim>
$ORIGIN element.tla.
test   10 IN A6 0 2002:6to4:prefix::

$ORIGIN test.element.tla.
helium 10 IN A6 0 ::1 test.element.tla.
</verbatim>

which is how I interpreted the bind9 docs on setting up A6 addressing. If i'm doing this wrong let me know. -- DanielLawson

''Some name servers (bind9?) support <tt>A6</tt> -> <tt>AAAA</tt> translations, can this be enabled?''

''I can find no mention of this. Bind9 supports A6 addresses in full, which are essentially identical to AAAA addresses, but thats not what I want''

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!NZ Zone Push Times

Added here for lack of ideas about a better page to put it on.

Currently the .nz zone push occurs every hour on the hour.

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See also:
* NameServer
* NamedNotes
* [DNSHowto]
* RFC:1034 (Domain Names -- Concepts and Facilities)
* RFC:1035 (Domain Names -- Implementations and Specification)
* [ICANN]

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Part of CategoryDns, CategoryNetworking and CategoryProtocols
81 pages link to DNS:
Last edited on Saturday, June 3, 2006 9:34:48 pm by MichaelJager
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