[Babel-users] AHCP and hostnames

[Dave Taht]

On Mon, Jan 7, 2013 at 12:06 PM, Juliusz Chroboczek <jch at pps.jussieu.fr> wrote:
>>> What application do you have in mind?
>
>> Assume no global connectivity, where do you register?
>
> With the DNS server advertised by AHCP?

With some sort of dynupdate facility, kind of ok, but it is faster to
do in the ahcp protocol and has the following benefits:

A) less round trips
B) less state mismatches - an address and name are assigned/deassigned
at the same time
C) it's how dhcp and dhcpv6 work  (not exactly a recomendation, yes)

 I don't know what simon has planned for dyn updates for dnsmasq

>> Since dnsmasq is rather common on just about everything embedded, and
>> doesn't support a dynupdate facility
>
> Oh, that's just an implementation detail.  (Famous last words.)
>
>> fe80::whatever routername.routers.mydomain.com
>
> You cannot do that -- link-local addresses are "scoped", they're only
> valid on a given link.  And the sockets API enforces that -- you
> cannot address a link-local address without specifying an interface
> number.

The point of a IPv6 fe80:: based dns extension is to be informational
rather than addressable.

eg:

fd86:c47f:b775:4::/64 via fe80::a021:b7ff:feb0:569f dev gw11  proto
zebra  metric 1024
fdd3:924:a0b6::/64 via fe80::de9f:dbff:fe21:302e dev se00  proto zebra
 metric 1024

vs:

daves-net via gw11.router1.routers.mydomain.org
bilbos-net via se00.router1.routers.mydomain.org

is way easier for humans. And tools exist.

>
> (Now you might argue that's a flaw in the spec, and that link-local
> addresses should be globally unique, but there are good reasons for
> that -- you really want link-local addresses to exist as soon as the
> interface is upped, even on hosts with no local storage and no MAC
> addresses.  For the anecdote, IPv6 originally defined a number of
> similar "scoped" addresses -- but all except the link-local addresses
> have been replaced by ULA.)


>> Would make interpreting babelweb data in particular easier.
>
> Use RFC 4620?  It's a much saner protocol than reverse DNS.

Perhaps.  I'll look it over.

Everybody does seem to want to toss everything into dns or mdns... but
I've stared at enough ULAs in the last few weeks to not want to stare
at them for the rest of my life.

>
> -- Juliusz



-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html