[MLB-WIRELESS] DNS and Locfinder

[Donovan Baarda]

On Fri, Nov 29, 2002 at 06:04:25AM +1100, evilbunny wrote:
> Hello James,
> 
> DNS was never meant to be a directory service, and I have no idea why
> people insist on confusing reverse and forward lookups into the mix as
> well. Doing a traceroute with anything as the forward lookup, won't
> show up in traceroute... then of course that would come down to a
> reverse lookup policy...
> 
> If you want a directory service I'd suggest taking a look at...

If you want directory service, why not LDAP? One cool thing this would allow
is allowing DNS access to the LDAP contents with ldapdns. There are plenty
of other tools that can access the ldap contents too, though it would be
slower than a native DNS service.

> ftp://ftp.cs.pdx.edu/pub/mobile/urld/ABOUT.txt
> ftp://ftp.cs.pdx.edu/pub/mobile/urld/urldv2.tar.gz
> ftp://ftp.cs.pdx.edu/pub/mobile/urld/urldv2.zip

I had a look at this and I can't really see how useful it is... It looks
more like an webserver advertisement service than a naming service.

> The reason for global DNS is simple, people that multihome, ie wireless
> and wired at the same time will have issues with non-public DNS
> structures, as DNS doesn't round robin as such, if it hits a DNS
> server (say the one issued by DHCP from optus, telstra etc) and it
> returns a not found record, it won't look at an internal one, on the
> flip side if they lookup google.com on an internal server and it is
> unable to locate it then of course it won't look else where it'll fail
> to find it...

The big problem with global DNS is you probably need global IP's to match...
does melbwireless have class C's to dish out?

I think it makes sense to use non-global DNS for non-global IP's. It is not
hard to configure things so that they work. 

multi-home sites will need two IP's (wired, and wireless), with the wired
having a GLOBAL DNS name, and the wireless having a non-global name. They
need to configure their system so that it will use upstream global DNS
servers for global names, and upstream wireless DNS servers for wireless
names. The easiest way to do this is run a caching nameserver that can be
configured to use the appropriate upstream DNS server. 

A simple caching dns server for this is pdnsd. It can be configured to use
different upstream servers for different queries.

For example, a multi-homed site could be

IP              FQDN                   Authoritative Server
172.16.1.1      node.melb.wireless.net ns.melb.wireless.net
203.12.237.9    node.apana.org.au      ns.melb.apana.org.au

Anyone who wants to be able to lookup both domains needs to configure their
DNS service to only use ns.melb.wireless.net for any queries for
*.melb.wireless.net or 172.16.*.*, and any global DNS server for everything
else.

> I'm definitely not in favour of long DNS names, this is self
> defeating, the whole point of DNS was to remove the need to remember
> IP addresses, and if you go off and do that, then others will
> most likely do what I'm planning to, run their own domains. It's
> neither difficult or expensive and turns the DNS issue into a
> non-debate as your still compliant with the rest of the internet...

long DNS names are OK, provided they are easy to remember. A short cryptic
DNS name is worse than a long obvious one.

-- 
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